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1.  HIV-1 Transmission during Early Infection in Men Who Have Sex with Men: A Phylodynamic Analysis 
PLoS Medicine  2013;10(12):e1001568.
Erik Volz and colleagues use HIV genetic information from a cohort of men who have sex with men in Detroit, USA to dissect the timing of onward transmission during HIV infection.
Please see later in the article for the Editors' Summary
Background
Conventional epidemiological surveillance of infectious diseases is focused on characterization of incident infections and estimation of the number of prevalent infections. Advances in methods for the analysis of the population-level genetic variation of viruses can potentially provide information about donors, not just recipients, of infection. Genetic sequences from many viruses are increasingly abundant, especially HIV, which is routinely sequenced for surveillance of drug resistance mutations. We conducted a phylodynamic analysis of HIV genetic sequence data and surveillance data from a US population of men who have sex with men (MSM) and estimated incidence and transmission rates by stage of infection.
Methods and Findings
We analyzed 662 HIV-1 subtype B sequences collected between October 14, 2004, and February 24, 2012, from MSM in the Detroit metropolitan area, Michigan. These sequences were cross-referenced with a database of 30,200 patients diagnosed with HIV infection in the state of Michigan, which includes clinical information that is informative about the recency of infection at the time of diagnosis. These data were analyzed using recently developed population genetic methods that have enabled the estimation of transmission rates from the population-level genetic diversity of the virus. We found that genetic data are highly informative about HIV donors in ways that standard surveillance data are not. Genetic data are especially informative about the stage of infection of donors at the point of transmission. We estimate that 44.7% (95% CI, 42.2%–46.4%) of transmissions occur during the first year of infection.
Conclusions
In this study, almost half of transmissions occurred within the first year of HIV infection in MSM. Our conclusions may be sensitive to un-modeled intra-host evolutionary dynamics, un-modeled sexual risk behavior, and uncertainty in the stage of infected hosts at the time of sampling. The intensity of transmission during early infection may have significance for public health interventions based on early treatment of newly diagnosed individuals.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Since the first recorded case of AIDS in 1981, the number of people infected with HIV, the virus that causes AIDS, has risen steadily. About 34 million people are currently HIV-positive, and about 2.5 million people become newly infected with HIV every year. Because HIV is usually transmitted through unprotected sex with an infected partner, individuals can reduce their risk of infection by abstaining from sex, by having only one or a few partners, and by always using condoms. Most people do not become ill immediately after infection with HIV, although some develop a short flu-like illness. The next stage of HIV infection, which may last more than ten years, also has no major symptoms, but during this stage, HIV slowly destroys immune system cells. Eventually, the immune system can no longer fight off infections by other disease-causing organisms, and HIV-positive people then develop one or more life-threatening AIDS-defining conditions, including unusual infections and specific types of cancer. HIV infection can be controlled, but not cured, by taking a daily cocktail of antiretroviral drugs.
Why Was This Study Done?
The design of effective programs to prevent the spread of HIV/AIDS depends on knowing how HIV transmissibility varies over the course of HIV infection. Consider, for example, a prevention strategy that focuses on increasing treatment rates: antiretroviral drugs, in addition to reducing illness and death among HIV-positive people, reduce HIV transmission from HIV-positive individuals. “Treatment as prevention” can only block transmissions that occur after diagnosis and entry into care. However, the transmissibility of HIV per sexual contact depends on a person's viral load, which peaks during early HIV infection, when people are often unaware of their HIV status and may still be following the high-risk patterns of sexual behavior that caused their own infection. Epidemiological surveillance data (information on HIV infections within populations) can be used to estimate how many new HIV infections occur within a population annually (HIV incidence) and the proportion of the population that is HIV-positive (HIV prevalence), but cannot be used to estimate the timing of transmission events. In this study, the researchers use “phylodynamic analysis” to estimate HIV incidence and prevalence and the timing of HIV transmission during infection. HIV, like many other viruses, rapidly accumulates genetic changes. The timing of transmission influences the pattern of these changes. Viral phylodynamic analysis—the quantitative study of how epidemiological, immunological, and evolutionary processes shape viral phylogenies (evolutionary trees)—can therefore provide estimates of transmission dynamics.
What Did the Researchers Do and Find?
The researchers obtained HIV sequence data (collected for routine surveillance of antiretroviral resistance mutations) and epidemiological surveillance data (including information on the stage of infection at diagnosis) for 662 HIV-positive men who have sex with men living in the Detroit metropolitan area of Michigan. They constructed a phylogenetic tree from the sequences using a “relaxed clock” approach and then fitted an epidemiological model (a mathematical model that represents the progress of individual patients through various stages of HIV infection) to the sequence data. Their approach, which integrates surveillance data and genetic data, yielded estimates of HIV incidence and prevalence among the study population similar to those obtained from surveillance data alone. However, it also provided information about HIV transmission that could not be obtained from surveillance data alone. In particular, it allowed the researchers to estimate that, in the current HIV epidemic among men who have sex with men in Detroit, 44.7% of HIV transmissions occur during the first year of infection.
What Do These Findings Mean?
The robustness of these findings depends on the validity of the assumptions included in the researchers' population genetic model and on the accuracy of the data fed into the model, and may not be generalizable to other cities or to other risk groups. Nevertheless, the findings of this analysis, which can be repeated in any setting where HIV sequence data for individual patients can be linked to patient-specific clinical and behavioral information, have important implications for HIV control strategies based on the early treatment of newly diagnosed individuals. Because relatively few infected individuals are diagnosed during early HIV infection, when the HIV transmission rate is high, it is unlikely, suggest the researchers, that the “treatment as prevention” strategy will effectively control the spread of HIV unless there are very high rates of HIV testing and treatment.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001568.
This study is further discussed in a PLOS Medicine Perspective by Timothy Hallett
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including information on HIV treatment as prevention (in English and Spanish)
The PLOS Medicine Collection Investigating the Impact of Treatment on New HIV Infections provides more information about HIV treatment as prevention
A PLOS Computational Biology Topic Page (a review article that is a published copy of record of a dynamic version of the article as found in Wikipedia) about viral phylodynamics is available
The US National Institute of Health–funded HIV Sequence Database contains HIV sequences and tools to analyze these sequences
Patient stories about living with HIV/AIDS are available through Avert; the charity website Healthtalkonline also provides personal stories about living with HIV
doi:10.1371/journal.pmed.1001568
PMCID: PMC3858227  PMID: 24339751
2.  The Role of Viral Introductions in Sustaining Community-Based HIV Epidemics in Rural Uganda: Evidence from Spatial Clustering, Phylogenetics, and Egocentric Transmission Models 
PLoS Medicine  2014;11(3):e1001610.
Using different approaches to investigate HIV transmission patterns, Justin Lessler and colleagues find that extra-community HIV introductions are frequent and likely play a role in sustaining the epidemic in the Rakai community.
Please see later in the article for the Editors' Summary
Background
It is often assumed that local sexual networks play a dominant role in HIV spread in sub-Saharan Africa. The aim of this study was to determine the extent to which continued HIV transmission in rural communities—home to two-thirds of the African population—is driven by intra-community sexual networks versus viral introductions from outside of communities.
Methods and Findings
We analyzed the spatial dynamics of HIV transmission in rural Rakai District, Uganda, using data from a cohort of 14,594 individuals within 46 communities. We applied spatial clustering statistics, viral phylogenetics, and probabilistic transmission models to quantify the relative contribution of viral introductions into communities versus community- and household-based transmission to HIV incidence. Individuals living in households with HIV-incident (n = 189) or HIV-prevalent (n = 1,597) persons were 3.2 (95% CI: 2.7–3.7) times more likely to be HIV infected themselves compared to the population in general, but spatial clustering outside of households was relatively weak and was confined to distances <500 m. Phylogenetic analyses of gag and env genes suggest that chains of transmission frequently cross community boundaries. A total of 95 phylogenetic clusters were identified, of which 44% (42/95) were two individuals sharing a household. Among the remaining clusters, 72% (38/53) crossed community boundaries. Using the locations of self-reported sexual partners, we estimate that 39% (95% CI: 34%–42%) of new viral transmissions occur within stable household partnerships, and that among those infected by extra-household sexual partners, 62% (95% CI: 55%–70%) are infected by sexual partners from outside their community. These results rely on the representativeness of the sample and the quality of self-reported partnership data and may not reflect HIV transmission patterns outside of Rakai.
Conclusions
Our findings suggest that HIV introductions into communities are common and account for a significant proportion of new HIV infections acquired outside of households in rural Uganda, though the extent to which this is true elsewhere in Africa remains unknown. Our results also suggest that HIV prevention efforts should be implemented at spatial scales broader than the community and should target key populations likely responsible for introductions into communities.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
About 35 million people (25 million of whom live in sub-Saharan Africa) are currently infected with HIV, the virus that causes AIDS, and about 2.3 million people become newly infected every year. HIV destroys immune system cells, leaving infected individuals susceptible to other infections. HIV infection can be controlled by taking antiretroviral drugs (antiretroviral therapy, or ART) daily throughout life. Although originally available only to people living in wealthy countries, recent political efforts mean that 9.7 million people in low- and middle-income countries now have access to ART. However, ART does not cure HIV infection, so prevention of viral transmission remains extremely important. Because HIV is usually transmitted through unprotected sex with an infected partner, individuals can reduce their risk of infection by abstaining from sex, by having one or a few partners, and by using condoms. Male circumcision also reduces HIV transmission. In addition to reducing illness and death among HIV-positive people, ART also reduces HIV transmission.
Why Was This Study Done?
Effective HIV control requires an understanding of how HIV spreads through sexual networks. These networks include sexual partnerships between individuals in households, between community members in different households, and between individuals from different communities. Local sexual networks (household and intra-community sexual partnerships) are sometimes assumed to be the dominant driving force in HIV spread in sub-Saharan Africa, but are viral introductions from sexual partnerships with individuals outside the community also important? This question needs answering because the effectiveness of interventions such as ART as prevention partly depends on how many new infections in an intervention area are attributable to infection from partners residing in that area and how many are attributable to infection from partners living elsewhere. Here, the researchers use three analytical methods—spatial clustering statistics, viral phylogenetics, and egocentric transmission modeling—to ask whether HIV transmission in rural Uganda is driven predominantly by intra-community sexual networks. Spatial clustering analysis uses the geographical coordinates of households to measure the tendency of HIV-infected people to cluster spatially at scales consistent with community transmission. Viral phylogenetic analysis examines the genetic relatedness of viruses; if transmission is through local networks, viruses in newly infected individuals should more closely resemble viruses in other community members than those in people outside the community. Egocentric transmission modelling uses information on the locations of recent sexual partners to estimate the proportions of new transmissions from household, intra-community, and extra-community partners.
What Did the Researchers Do and Find?
The researchers applied their three analytical methods to data collected from 14,594 individuals living in 46 communities (governmental administrative units) in Rakai District, Uganda. Spatial clustering analysis indicated that individuals who lived in households with individuals with incident HIV (newly diagnosed) or prevalent HIV (previously diagnosed) were 3.2 times more likely than the general population to be HIV-positive themselves. Spatial clustering outside households was relatively weak, however, and was confined to distances of less than half a kilometer. Viral phylogenetic analysis indicated that 44% of phylogenetic clusters (viruses with related genetic sequences found in more than one individual) were within households, but that 40% of clusters crossed community borders. Finally, analysis of the locations of self-reported sexual partners indicated that 39% of new viral transmissions occurred within stable household partnerships, but that among people newly infected by extra-household partners, nearly two-thirds were infected by partners from outside their community.
What Do These Findings Mean?
The results of all three analyses suggest that HIV introductions into communities are frequent and are likely to play an important role in sustaining HIV transmission in the Rakai District. Specifically, within this rural HIV-endemic region (a region where HIV infection is always present), viral introductions combined with intra-household transmission account for the majority of new infections, although community-based sexual networks also play a critical role in HIV transmission. These findings may not be generalizable to the broader Ugandan population or to other regions of Africa, and their accuracy is likely to be limited by the use of self-reported sexual partner data. Nevertheless, these findings indicate that the dynamics of HIV transmission in rural Uganda (and probably elsewhere) are complex. Consequently, to halt the spread of HIV, prevention efforts will need to be implemented at spatial scales broader than individual communities, and key populations that are likely to introduce HIV into communities will need to be targeted.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001610.
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS, and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including information on HIV and AIDS in Uganda and on HIV prevention strategies (in English and Spanish)
The UNAIDS Report on the Global AIDS Epidemic 2013 provides up-to-date information about the AIDS epidemic and efforts to halt it
The Center for AIDS Prevention Studies (University of California, San Francisco) has a fact sheet about sexual networks and HIV prevention
Wikipedia provides information on spatial clustering analysis (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
A PLOS Computational Biology Topic Page (a review article that is a published copy of record of a dynamic version of the article as found in Wikipedia) about viral phylodynamics is available
Personal stories about living with HIV/AIDS are available through Avert, NAM/aidsmap, and Healthtalkonline
doi:10.1371/journal.pmed.1001610
PMCID: PMC3942316  PMID: 24595023
3.  Incident HIV during Pregnancy and Postpartum and Risk of Mother-to-Child HIV Transmission: A Systematic Review and Meta-Analysis 
PLoS Medicine  2014;11(2):e1001608.
Alison Drake and colleagues conduct a systematic review and meta-analysis to estimate maternal HIV incidence during pregnancy and the postpartum period and to compare mother-to-child HIV transmission risk among women with incident versus chronic infection.
Please see later in the article for the Editors' Summary
Background
Women may have persistent risk of HIV acquisition during pregnancy and postpartum. Estimating risk of HIV during these periods is important to inform optimal prevention approaches. We performed a systematic review and meta-analysis to estimate maternal HIV incidence during pregnancy/postpartum and to compare mother-to-child HIV transmission (MTCT) risk among women with incident versus chronic infection.
Methods and Findings
We searched PubMed, Embase, and AIDS-related conference abstracts between January 1, 1980, and October 31, 2013, for articles and abstracts describing HIV acquisition during pregnancy/postpartum. The inclusion criterion was studies with data on recent HIV during pregnancy/postpartum. Random effects models were constructed to pool HIV incidence rates, cumulative HIV incidence, hazard ratios (HRs), or odds ratios (ORs) summarizing the association between pregnancy/postpartum status and HIV incidence, and MTCT risk and rates. Overall, 1,176 studies met the search criteria, of which 78 met the inclusion criterion, and 47 contributed data. Using data from 19 cohorts representing 22,803 total person-years, the pooled HIV incidence rate during pregnancy/postpartum was 3.8/100 person-years (95% CI 3.0–4.6): 4.7/100 person-years during pregnancy and 2.9/100 person-years postpartum (p = 0.18). Pooled cumulative HIV incidence was significantly higher in African than non-African countries (3.6% versus 0.3%, respectively; p<0.001). Risk of HIV was not significantly higher among pregnant (HR 1.3, 95% CI 0.5–2.1) or postpartum women (HR 1.1, 95% CI 0.6–1.6) than among non-pregnant/non-postpartum women in five studies with available data. In African cohorts, MTCT risk was significantly higher among women with incident versus chronic HIV infection in the postpartum period (OR 2.9, 95% CI 2.2–3.9) or in pregnancy/postpartum periods combined (OR 2.3, 95% CI 1.2–4.4). However, the small number of studies limited power to detect associations and sources of heterogeneity.
Conclusions
Pregnancy and the postpartum period are times of persistent HIV risk, at rates similar to “high risk” cohorts. MTCT risk was elevated among women with incident infections. Detection and prevention of incident HIV in pregnancy/postpartum should be prioritized, and is critical to decrease MTCT.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Worldwide, about 3.4 million children younger than 15 years old (mostly living in sub-Saharan Africa) are infected with HIV, the virus that causes AIDS by gradually destroying immune system cells, thereby leaving infected individuals susceptible to other serious infections. In 2012 alone, 230,000 children (more than 700 every day) were newly infected with HIV. Most HIV infections among children are the result of mother-to-child HIV transmission (MTCT) during pregnancy, delivery, or breastfeeding. The rate of MTCT (and deaths among HIV-positive pregnant women from complications related to HIV infection) can be greatly reduced by testing women for HIV infection during pregnancy (antenatal HIV testing), treating HIV-positive women with antiretroviral drugs (ARVs, powerful drugs that control HIV replication and allow the immune system to recover) during pregnancy, delivery, and breastfeeding, and giving ARVs to their newborn babies.
Why Was This Study Done?
The World Health Organization and the Joint United Nations Programme on HIV/AIDS (UNAIDS) have developed a global plan that aims to move towards eliminating new HIV infections among children by 2015 and towards keeping their mothers alive. To ensure the plan's success, the incidence of HIV (the number of new infections) among women and the rate of MTCT must be reduced by increasing ARV uptake by mothers and their infants for the prevention of MTCT. However, the risk of HIV infection among pregnant women and among women who have recently given birth (postpartum women) is poorly understood because, although guidelines recommend repeat HIV testing during late pregnancy or at delivery in settings where HIV infection is common, pregnant women are often tested only once for HIV infection. The lack of retesting represents a missed opportunity to identify pregnant and postpartum women who have recently acquired HIV and to prevent MTCT by initiating ARV therapy. In this systematic review (a study that uses predefined criteria to identify all the research on a given topic) and meta-analysis (a study that uses statistical methods to combine the results of several studies), the researchers estimate maternal HIV incidence during pregnancy and the postpartum period, and compare the risk of MTCT among women with incident (new) and chronic (long-standing) HIV infection.
What Did the Researchers Do and Find?
The researchers identified 47 studies (35 undertaken in Africa) that examined recent HIV acquisition by women during pregnancy and the 12-month postpartum period. They used random effects statistical models to estimate the pooled HIV incidence rate and cumulative HIV incidence (the number of new infections per number of people at risk), and the association between pregnancy/postpartum status and HIV incidence and MTCT risk and rates. The pooled HIV incidence rate among pregnant/postpartum women estimated from 19 studies (all from sub-Saharan Africa) that reported HIV incidence rates was 3.8/100 person-years. The pooled cumulative HIV incidence was significantly higher in African countries than in non-African countries (3.6% and 0.3%, respectively; a “significant” difference is one that is unlikely to arise by chance). In the five studies that provided suitable data, the risk of HIV acquisition was similar in pregnant, postpartum, and non-pregnant/non-postpartum women. Finally, among African women, the risk of MTCT was 2.9-fold higher during the postpartum period among those who had recently acquired HIV than among those with chronic HIV infection, and 2.3-fold higher during the pregnancy/postpartum periods combined.
What Do These Findings Mean?
These results suggest that women living in regions where HIV infection is common are at high risk of acquiring HIV infection during pregnancy and the postpartum period and that mothers who acquire HIV during pregnancy or postpartum are more likely to pass the infection on to their offspring than mothers with chronic HIV infections. However, the small number of studies included in this meta-analysis and the use of heterogeneous research methodologies in these studies may limit the accuracy of these findings. Nevertheless, these findings have important implications for the global plan to eliminate HIV infections in children. First, they suggest that women living in regions where HIV infection is common should be offered repeat HIV testing (using sensitive methods to enhance early detection of infection) during pregnancy and in the postpartum period to detect incident HIV infections, and should be promptly referred to HIV care and treatment. Second, they suggest that prevention of HIV transmission during pregnancy and postpartum should be prioritized, for example, by counseling women about the need to use condoms to prevent transmission during this period of their lives.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001608.
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including information on children and HIV/AIDS and on the prevention of mother-to-child transmission of HIV (in English and Spanish)
The 2013 UNAIDS World AIDS Day Report provides information about the AIDS epidemic and efforts to halt it; the 2013 UNAIDS Progress Report on the Global Plan provides information on progress towards eliminating new HIV infections among children; the UNAIDS Believe it. Do it website provides information about the campaign to support the UNAIDS global plan
Personal stories about living with HIV/AIDS, including stories from young people infected with HIV, are available through Avert, NAM/aidsmap, and Healthtalkonline
doi:10.1371/journal.pmed.1001608
PMCID: PMC3934828  PMID: 24586123
4.  Elimination of HIV in South Africa through Expanded Access to Antiretroviral Therapy: A Model Comparison Study 
PLoS Medicine  2013;10(10):e1001534.
Using nine structurally different models, Jan Hontelez and colleagues investigate timeframes for HIV elimination in South Africa using a universal test and treat strategy.
Please see later in the article for the Editors' Summary
Background
Expanded access to antiretroviral therapy (ART) using universal test and treat (UTT) has been suggested as a strategy to eliminate HIV in South Africa within 7 y based on an influential mathematical modeling study. However, the underlying deterministic model was criticized widely, and other modeling studies did not always confirm the study's finding. The objective of our study is to better understand the implications of different model structures and assumptions, so as to arrive at the best possible predictions of the long-term impact of UTT and the possibility of elimination of HIV.
Methods and Findings
We developed nine structurally different mathematical models of the South African HIV epidemic in a stepwise approach of increasing complexity and realism. The simplest model resembles the initial deterministic model, while the most comprehensive model is the stochastic microsimulation model STDSIM, which includes sexual networks and HIV stages with different degrees of infectiousness. We defined UTT as annual screening and immediate ART for all HIV-infected adults, starting at 13% in January 2012 and scaled up to 90% coverage by January 2019. All models predict elimination, yet those that capture more processes underlying the HIV transmission dynamics predict elimination at a later point in time, after 20 to 25 y. Importantly, the most comprehensive model predicts that the current strategy of ART at CD4 count ≤350 cells/µl will also lead to elimination, albeit 10 y later compared to UTT. Still, UTT remains cost-effective, as many additional life-years would be saved. The study's major limitations are that elimination was defined as incidence below 1/1,000 person-years rather than 0% prevalence, and drug resistance was not modeled.
Conclusions
Our results confirm previous predictions that the HIV epidemic in South Africa can be eliminated through universal testing and immediate treatment at 90% coverage. However, more realistic models show that elimination is likely to occur at a much later point in time than the initial model suggested. Also, UTT is a cost-effective intervention, but less cost-effective than previously predicted because the current South African ART treatment policy alone could already drive HIV into elimination.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
About 34 million people (mostly in low- and middle-income countries) are currently infected with HIV, the virus that causes AIDS, and every year another 2.5 million people become infected. HIV, which is usually transmitted through unprotected sex with an infected partner, gradually destroys CD4 lymphocytes and other immune system cells, leaving infected individuals susceptible to other infections. Early in the AIDS epidemic, people infected with HIV often died within ten years of infection. Then, in 1996, antiretroviral therapy (ART) became available, and, for people living in affluent countries, HIV/AIDS became a chronic condition. However, ART was expensive, so HIV/AIDS remained a fatal condition for people living in resource-limited countries. In 2006, the international community set a target of achieving universal ART coverage by 2010, and ART programs were initiated in many resource-limited countries. Although universal ART coverage has still not been achieved in South Africa, where nearly 6 million people are HIV-positive, 80% of people in need of ART were receiving a World Health Organization–recommended ART regimen by October 2012.
Why Was This Study Done?
ART is usually started when a person's CD4 count falls below 350 cells/µl blood, but it is thought that treatment of all HIV-positive individuals, regardless of their CD4 count, could reduce HIV transmission by reducing the infectiousness of HIV-positive individuals (“treatment as prevention”). Might it be possible, therefore, to eliminate HIV by screening everyone annually for infection and treating all HIV-positive individuals immediately? In 2009, a mathematical modeling study suggested that seven years of universal test and treat (UTT) could eliminate HIV in South Africa. The deterministic (nonrandom) model used in that study has been widely criticized, however, and some subsequent modeling studies have reached different conclusions, probably because of differences in the models' structures and in the assumptions built into them. A better understanding of the reasons for the discrepancies between models would help policy-makers decide whether to introduce UTT, so, here, the researchers developed several increasingly complex and realistic models of the South African HIV epidemic and used these models to predict the long-term impact of UTT in South Africa.
What Did the Researchers Do and Find?
The researchers developed nine structurally different mathematical models of the South African HIV epidemic based on the STDSIM framework, a stochastic microsimulation model that simulates the life course of individuals in a dynamic network of sexual contacts and in which events such as HIV infection are random processes. The simplest model, which resembled the original deterministic model, was extended by sequentially adding in factors such as different HIV transmission rates at different stages of HIV infection and up-to-date assumptions regarding the ability of ART to reduce HIV infectiousness. All the models replicated the prevalence of HIV in South Africa (the proportion of the population that was HIV-positive) between 1990 and 2010, and all predicted that UTT (defined as annual screening of individuals age 15+ years and immediate ART for all HIV-infected adults starting in 2012 and scaled up to 90% coverage by 2019) would result in HIV elimination (less than one new infection per 1,000 person-years). However, whereas the simplest model predicted that UTT would eliminate HIV after seven years, the more complex, realistic models predicted elimination at much later time points. Importantly, the most comprehensive model predicted that, although elimination would be reached after about 17 years of UTT, the current strategy of ART initiation for HIV-positive individuals at a CD4 cell count at or below 350 cells/µl would also lead to HIV elimination, albeit ten years later than UTT.
What Do These Findings Mean?
These findings confirm previous predictions that UTT could eliminate HIV in South Africa, but the development of more realistic models than those used in the past suggests that HIV elimination would occur substantially later than originally predicted. Importantly, the most comprehensive model suggests that HIV could be eliminated in South Africa using the current strategy for ART treatment alone. As with all modeling studies, the accuracy of these findings depends on the assumptions built into the models and on the structure of the models. Thus, although these findings support the use of UTT as an intervention to eliminate HIV, more research with comprehensive models that incorporate factors such as data from ongoing trials of treatment as prevention is needed to determine the population-level impact and overall cost-effectiveness of UTT.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001534.
This study is further discussed in a PLOS Medicine Perspective by Ford and Hirnschall
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including information on HIV and AIDS in South Africa, on HIV treatment as prevention and the possibility of HIV elimination (in English and Spanish)
The 2012 UNAIDS World AIDS Day Report provides up-to-date information about the AIDS epidemic and efforts to halt it
The World Health Organization provides information about universal access to AIDS treatment (in several languages); its 2010 ART guidelines can be downloaded
The PLOS Medicine Collection Investigating the Impact of Treatment on New HIV Infections provides more information about HIV treatment as prevention
Personal stories about living with HIV/AIDS are available through Avert, through NAM/aidsmap, and through the charity website Healthtalkonline
doi:10.1371/journal.pmed.1001534
PMCID: PMC3805487  PMID: 24167449
5.  The Potential Impact of Male Circumcision on HIV in Sub-Saharan Africa 
PLoS Medicine  2006;3(7):e262.
Background
A randomized controlled trial (RCT) has shown that male circumcision (MC) reduces sexual transmission of HIV from women to men by 60% (32%−76%; 95% CI) offering an intervention of proven efficacy for reducing the sexual spread of HIV. We explore the implications of this finding for the promotion of MC as a public health intervention to control HIV in sub-Saharan Africa.
Methods and Findings
Using dynamical simulation models we consider the impact of MC on the relative prevalence of HIV in men and women and in circumcised and uncircumcised men. Using country level data on HIV prevalence and MC, we estimate the impact of increasing MC coverage on HIV incidence, HIV prevalence, and HIV-related deaths over the next ten, twenty, and thirty years in sub-Saharan Africa. Assuming that full coverage of MC is achieved over the next ten years, we consider three scenarios in which the reduction in transmission is given by the best estimate and the upper and lower 95% confidence limits of the reduction in transmission observed in the RCT.
MC could avert 2.0 (1.1−3.8) million new HIV infections and 0.3 (0.1−0.5) million deaths over the next ten years in sub-Saharan Africa. In the ten years after that, it could avert a further 3.7 (1.9−7.5) million new HIV infections and 2.7 (1.5−5.3) million deaths, with about one quarter of all the incident cases prevented and the deaths averted occurring in South Africa. We show that a) MC will increase the proportion of infected people who are women from about 52% to 58%; b) where there is homogenous mixing but not all men are circumcised, the prevalence of infection in circumcised men is likely to be about 80% of that in uncircumcised men; c) MC is equivalent to an intervention, such as a vaccine or increased condom use, that reduces transmission in both directions by 37%.
Conclusions
This analysis is based on the result of just one RCT, but if the results of that trial are confirmed we suggest that MC could substantially reduce the burden of HIV in Africa, especially in southern Africa where the prevalence of MC is low and the prevalence of HIV is high. While the protective benefit to HIV-negative men will be immediate, the full impact of MC on HIV-related illness and death will only be apparent in ten to twenty years.
Editors' Summary
Background.
Africa is the continent most affected by HIV/AIDS, and it is important to consider all possible means of reducing the spread of HIV infection. Male circumcision has been a tradition in many parts of Africa for hundreds of years. Boys who are circumcised usually have it done in late childhood or their early teenage years. It was noticed some years ago that those African groups in which circumcision is routinely done on all boys have fewer cases of HIV/AIDS than are found in groups where circumcision is not a tradition. This finding gave rise to the idea that circumcision might give a degree of protection against HIV, though it was recognised that some other, unknown difference between these groups of people might actually be the important factor. In 2005 a trial was reported from the Orange Farm area of South Africa, in which uncircumcised men were offered the chance to be circumcised. The men who agreed were divided at random into those who had the operation straightaway and those who were to have it two years later. During the next 18 months, the number of new cases of HIV infection was much higher amongst the men who had not been circumcised. Circumcision did therefore seem to offer a measure of protection against infection. This protective effect was estimated at being about 60%. Similar trials are under way in other parts of Africa but there are no results available from them at this stage.
Why Was This Study Done?
If the level of effectiveness of circumcision suggested by the South African trial is correct, then, as one part of a range of measures to reduce the spread of HIV, it would seem logical to encourage the practice of male circumcision. It would be useful to have an estimate of just how many new cases could be prevented and how many lives would be saved by the promotion of male circumcision. Calculations would have to allow for various factors, such as the present level of HIV infection, which varies from one country to another, and the fact that many men are already circumcised.
What Did the Researchers Do and Find?
This research did not involve collecting any new data. The researchers used mathematical modelling to make calculations. They based their model on data from the Orange Farm trial and on information from various sub-Saharan African countries on the proportion of men who are circumcised and the proportion who are HIV-positive. They made the assumption that if circumcision is intensively promoted, all men in those countries will be circumcised in 10 years time. They calculated the number of new cases that would be prevented and the lives that would be saved in ten years, 20 years, and 30 years time. Their best estimate is that with the promotion of male circumcision, two million cases and 0.3 million deaths will be avoided in ten years time. Over the following ten years, according to the researchers' model, a further 3.7 million cases and 2.7 million deaths would be prevented. Most of the initial impact would be in men, but the reduction in the number of HIV-positive men would in time also lower the risk of women becoming infected. Overall, on the basis of these calculations, male circumcision would reduce the rate of infections by about 37%—both female-to-male and male-to-female transmission. The size of the impact would vary from one country to another; it would be greatest in southern Africa where HIV infection rates are high and circumcision rates relatively low compared with the rest of sub-Saharan Africa.
What Do These Findings Mean?
Male circumcision alone cannot bring the HIV/AIDS epidemic in Africa under control. Even circumcised men can become infected, though their risk of doing so is much lower. However, the researchers call for the promotion of male circumcision to become a major part of AIDS control programmes. Their results are based on the findings of just one study (the Orange Farm trial), and it will be important to repeat the calculations when further studies have been completed.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0030262:
• The Orange Farm trial was published in PLoS Medicine. Several articles discussing the trial were also published in the same issue of the journal
• The Joint United Nations Programme on HIV/AIDS (UNAIDS) has information about the state of the HIV/AIDS epidemic and prevention strategies worldwide. It produces an annual report and has documents on a wide range of topics
•  AEGIS is the world's largest searchable database on HIV and AIDS.
• Many organizations provide information on AIDS prevention—for example, the Terrence Higgins Trust
• The World Bank's Global HIV/AIDS Program has a report about male circumcision and HIV infection
A modelling study, based on one trial plus national figures for current prevalence of HIV and of male circumcision (MC), found increasing MC in Africa could produce major fall in HIV prevalence in 10-12 years.
doi:10.1371/journal.pmed.0030262
PMCID: PMC1489185  PMID: 16822094
6.  Bacterial Vaginosis Associated with Increased Risk of Female-to-Male HIV-1 Transmission: A Prospective Cohort Analysis among African Couples 
PLoS Medicine  2012;9(6):e1001251.
In a prospective study, Craig Cohen and colleagues investigate the association between bacterial vaginosis and the risk of female-to-male HIV-1 transmission.
Background
Bacterial vaginosis (BV), a disruption of the normal vaginal flora, has been associated with a 60% increased risk of HIV-1 acquisition in women and higher concentration of HIV-1 RNA in the genital tract of HIV-1–infected women. However, whether BV, which is present in up to half of African HIV-1–infected women, is associated with an increase in HIV-1 transmission to male partners has not been assessed in previous studies.
Methods and Findings
We assessed the association between BV on female-to-male HIV-1 transmission risk in a prospective study of 2,236 HIV-1–seropositive women and their HIV-1 uninfected male partners from seven African countries from a randomized placebo-controlled trial that enrolled heterosexual African adults who were seropositive for both HIV-1 and herpes simplex virus (HSV)-2, and their HIV-1–seronegative partners. Participants were followed for up to 24 months; every three months, vaginal swabs were obtained from female partners for Gram stain and male partners were tested for HIV-1. BV and normal vaginal flora were defined as a Nugent score of 7–10 and 0–3, respectively. To reduce misclassification, HIV-1 sequence analysis of viruses from seroconverters and their partners was performed to determine linkage of HIV-1 transmissions. Overall, 50 incident HIV-1 infections occurred in men in which the HIV-1–infected female partner had an evaluable vaginal Gram stain. HIV-1 incidence in men whose HIV-1–infected female partners had BV was 2.91 versus 0.76 per 100 person-years in men whose female partners had normal vaginal flora (hazard ratio 3.62, 95% CI 1.74–7.52). After controlling for sociodemographic factors, sexual behavior, male circumcision, sexually transmitted infections, pregnancy, and plasma HIV-1 RNA levels in female partners, BV was associated with a greater than 3-fold increased risk of female-to-male HIV-1 transmission (adjusted hazard ratio 3.17, 95% CI 1.37–7.33).
Conclusions
This study identified an association between BV and increased risk of HIV-1 transmission to male partners. Several limitations may affect the generalizability of our results including: all participants underwent couples HIV counseling and testing and enrolled in an HIV-1 prevention trial, and index participants had a baseline CD4 count ≥250 cells/mm3 and were HSV-2 seropositive. Given the high prevalence of BV and the association of BV with increased risk of both female HIV-1 acquisition and transmission found in our study, if this association proves to be causal, BV could be responsible for a substantial proportion of new HIV-1 infections in Africa. Normalization of vaginal flora in HIV-1–infected women could mitigate female-to-male HIV-1 transmission.
Trial Registration: ClinicalTrials.com NCT00194519
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Since the first reported case of AIDS in 1981, the number of people infected with HIV, the virus that causes AIDS, has risen steadily. By the end of 2010, 34 million people were living with HIV/AIDS. At the beginning of the epidemic more men than women were infected with HIV. Now, however, 50% of all adults infected with HIV are women and in sub-Saharan Africa, where two-thirds of HIV-positive people live, women account for 59% of people living with HIV. Moreover, among 15–24 year-olds, women are eight times more likely than men to be HIV-positive. This pattern of infection has developed because most people in sub-Saharan Africa contract HIV through unprotected heterosexual sex. The risk of HIV transmission for both men and women in Africa and elsewhere can be reduced by abstaining from sex, by only having one or a few partners, by always using condoms, and by male circumcision. In addition, several studies suggest that antiretroviral therapy (ART) greatly reduces HIV transmission.
Why Was This Study Done?
Unfortunately, in sub-Saharan Africa, only about a fifth of HIV-positive people are currently receiving ART, which means that there is an urgent need to find other effective ways to reduce HIV transmission in this region. In this prospective cohort study (a type of study that follows a group of people for some time to see which personal characteristics are associated with disease development), the researchers investigate whether bacterial vaginosis—a condition in which harmful bacteria disrupt the normal vaginal flora—increases the risk of female-to-male HIV transmission among African couples. Bacterial vaginosis, which is extremely common in sub-Saharan Africa, has been associated with an increased risk of HIV acquisition in women and induces viral replication and shedding in the vagina in HIV-positive women, which may mean that HIV-positive women with bacterial vaginosis are more likely to transmit HIV to their male partners than women without this condition. If this is the case, then interventions that reduce the incidence of bacterial vaginosis might be valuable HIV prevention strategies.
What Did the Researchers Do and Find?
The researchers analyzed data collected from 2,236 heterosexual African couples enrolled in a clinical trial (the Partners in Prevention HSV/HIV Transmission Study) whose primary aim was to investigate whether suppression of herpes simplex virus infection could prevent HIV transmission. In all the couples, the woman was HIV-positive and the man was initially HIV-negative. The female partners were examined every three months for the presence of bacterial vaginosis and the male partners were tested regularly for HIV infection. The researchers also determined whether the men who became HIV-positive were infected with the same HIV strain as their partner to check that their infection had been acquired from this partner. The HIV incidence in men whose partners had bacterial vaginosis was 2.9 per 100 person-years (that is, 2.9 out of every 100 men became HIV-positive per year) whereas the HIV incidence in men whose partners had a normal vaginal flora was 0.76 per 100 person-years. After controlling for factors that might affect the risk of HIV transmission such as male circumcision and viral levels in female partner's blood, the researchers estimated that bacterial vaginosis was associated with a 3.17-fold increased risk of female-to-male HIV transmission in their study population.
What Do These Findings Mean?
These findings suggest that HIV-positive African women with bacterial vaginosis are more than three times as likely to transmit HIV to their male partners as those with a normal vaginal flora. It is possible that some unknown characteristic of the men in this study might have increased both their own risk of HIV infection and their partner's risk of bacterial vaginosis. Nevertheless, because bacterial vaginosis is so common in Africa (half of the women in this study had bacterial vaginosis at least once during follow-up) and because this condition is associated with both female HIV acquisition and transmission, these findings suggest that bacterial vaginosis could be responsible for a substantial proportion of new HIV infections in Africa. Normalization of vaginal flora in HIV-infected women by frequent presumptive treatment with antimicrobials (treatment with a curative dose of antibiotics without testing for bacterial vaginosis) or possibly by treatment with probiotics (live “good” bacteria) might, therefore, reduce female-to-male HIV transmission in sub-Saharan Africa.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001251.
Information is available from the US National Institute of Allergy and infectious diseases on all aspects of HIV infection and AIDS and on bacterial vaginosis
The US Centers for Disease Control and Prevention has information on all aspects of HIV/AIDS, including specific information about HIV/AIDS and women; it also has information on bacterial vaginosis (in English and Spanish)
NAM/aidsmap provides basic information about HIV/AIDS, and summaries of recent research findings on HIV care and treatment, and information on bacterial vaginosis and HIV transmission (in several languages)
Information is available from Avert, an international AIDS nonprofit group on many aspects of HIV/AIDS, including detailed information on HIV and AIDS prevention, on women, HIV and AIDS and on HIV/AIDS in Africa (in English and Spanish); personal stories of women living with HIV are available; the website Healthtalkonline also provides personal stories about living with HIV
More information about the Partners in Prevention HSV/HIV Transmission Study is available
doi:10.1371/journal.pmed.1001251
PMCID: PMC3383741  PMID: 22745608
7.  Polymorphisms in TLR4 and TLR9 influence viral load in a sero-incident cohort of HIV-1-infected individuals 
AIDS (London, England)  2009;23(18):2387-2395.
OBJECTIVES
Toll-like receptors (TLR) are innate immune sensors that are integral to resisting chronic and opportunistic infections. Mounting evidence implicates TLR polymorphisms in susceptibilities to various infectious diseases, including HIV-1. We investigated the impact of TLR single-nucleotide polymorphisms (SNPs) on clinical outcome in a sero-incident cohort of HIV-1-infected volunteers.
DESIGN
We analyzed TLR SNPs in 201 antiretroviral treatment-naïve HIV-1 infected subjects from a longitudinal sero-incident cohort with regular follow-up intervals (median follow-up 4.2 years, interquartile range 4.4). Subjects were stratified into two groups according to either disease progression, defined as peripheral blood CD4+ T-cell decline over time, or peak and setpoint viral load.
METHODS
Haplotype-tagging SNPs from TLR2, TLR3, TLR4, and TLR9 were detected by mass-array genotyping, and CD4+ T-cell counts and viral load measurements were determined prior to antiretroviral therapy initiation. The association of TLR haplotypes with viral load and rapid progression was assessed by multivariate regression models using age and sex as covariates.
RESULTS
Two TLR4 SNPs in strong linkage disequilibrium (1063A/G [D299G] and 1363C/T [T399I]) were more frequent among subjects with high peak viral load compared to low/moderate peak viral load (OR=6.65, 95% CI 2.19–20.46, P<0.001; adjusted P=0.002 for 1063A/G). In addition, a TLR9 SNP previously associated with slow progression was found less frequently among subjects with high viral setpoint compared to low/moderate setpoint (OR=0.29, 95% CI 0.13–0.65, P=0.003, adjusted P=0.04).
CONCLUSION
This study suggests a potentially new role for TLR4 polymorphisms in HIV-1 peak viral load and confirms a role for TLR9 polymorphisms in disease progression.
doi:10.1097/QAD.0b013e328330b489
PMCID: PMC2919356  PMID: 19855253
HIV-1; Innate Immunity; HIV genetics; HIV immunology; Single Nucleotide Polymorphism; Toll-Like Receptor 9; Toll-Like Receptor 4
8.  Recent HIV-1 Infection: Identification of Individuals with High Viral Load Setpoint in a Voluntary Counselling and Testing Centre in Rural Mozambique 
PLoS ONE  2012;7(2):e31859.
Background
Identification of recent HIV-infections is important for describing the HIV epidemic and compiling HIV-RNA-setpoint data for future HIV intervention trials. We conducted a study to characterize recent infections, and HIV-RNA-setpoint within the adult population presenting at a voluntary counselling and testing centre (VCT) in southern Mozambique.
Methods
All adults attending the Manhiça District-Hospital VCT between April and October 2009 were recruited if they had at least one positive rapid HIV-serology test. Patients were screened for recent HIV-1 infection by BED-CEIA HIV-incidence test. Clinical examination, assessment of HIV-RNA and CD4 cell counts were performed at enrollment, 4 and 10 months.
Results
Of the 492 participants included in this study, the prevalence of recent infections as defined by BED-CEIA test, CD4 counts >200 cells/µl and HIV-RNA >400 copies/mL, was 11.58% (57/492; 95% CI 8.89–14.74). Due to heterogeneity in HIV-RNA levels in recently infected patients, individuals were categorized as having “high” HIV-RNA load if their HIV-RNA level was above the median (4.98 log10 copies/mL) at diagnosis. The “high” HIV-RNA group sustained a significantly higher HIV-viral load at all visits with a median HIV-RNA setpoint of 5.22 log10 copies/mL (IQR 5.18–5.47) as compared to the median of 4.15 log10 copies/ml (IQR 3.37–4.43) for the other patients (p = 0.0001).
Conclusion
The low proportion of recent HIV-infections among HIV-seropositive VCT clients suggests that most of this population attends the VCT at later stages of HIV/AIDS. Characterization of HIV-RNA-setpoint may serve to identify recently infected individuals maintaining HIV viral load>5 log10 copies/mL as candidates for antiretroviral treatment as prevention interventions.
doi:10.1371/journal.pone.0031859
PMCID: PMC3283689  PMID: 22363755
9.  Timing and source of subtype-C HIV-1 superinfection in the newly infected partner of Zambian couples with disparate viruses 
Retrovirology  2012;9:22.
Background
HIV-1 superinfection occurs at varying frequencies in different at risk populations. Though seroincidence is decreased, in the negative partner of HIV-discordant couples after joint testing and counseling in the Zambia Emory HIV Research Project (ZEHRP) cohort, the annual infection rate remains relatively high at 7-8%. Based on sequencing within the gp41 region of each partner's virus, 24% of new infections between 2004 and 2008 were the result of transmission from a non-spousal partner. Since these seroconvertors and their spouses have disparate epidemiologically-unlinked viruses, there is a risk of superinfection within the marriage. We have, therefore, investigated the incidence and viral origin of superinfection in these couples.
Results
Superinfection was detected by heteroduplex mobility assay (HMA), degenerate base counting of the gp41 sequence, or by phylogenetic analysis of the longitudinal sequences. It was confirmed by full-length env single genome amplification and phylogenetic analysis. In 22 couples (44 individuals), followed for up to five years, three of the newly infected (initially HIV uninfected) partners became superinfected. In each case superinfection occurred during the first 12 months following initial infection of the negative partner, and in each case the superinfecting virus was derived from a non-spousal partner. In addition, one probable case of intra-couple HIV-1 superinfection was observed in a chronically infected partner at the time of his seroconverting spouse's initial viremia. Extensive recombination within the env gene was observed following superinfection.
Conclusions
In this subtype-C discordant couple cohort, superinfection, during the first year after HIV-1 infection of the previously negative partner, occurred at a rate similar to primary infection (13.6% [95% CI 5.2-34.8] vs 7.8% [7.1-8.6]). While limited intra-couple superinfection may in part reflect continued condom usage within couples, this and our lack of detecting newly superinfected individuals after one year of primary infection raise the possibility that immunological resistance to intra-subtype superinfection may develop over time in subtype C infected individuals.
doi:10.1186/1742-4690-9-22
PMCID: PMC3349552  PMID: 22433432
10.  Identifying HIV-1 dual infections 
Retrovirology  2007;4:67.
Transmission of human immunodeficiency virus (HIV) is no exception to the phenomenon that a second, productive infection with another strain of the same virus is feasible. Experiments with RNA viruses have suggested that both coinfections (simultaneous infection with two strains of a virus) and superinfections (second infection after a specific immune response to the first infecting strain has developed) can result in increased fitness of the viral population. Concerns about dual infections with HIV are increasing. First, the frequent detection of superinfections seems to indicate that it will be difficult to develop a prophylactic vaccine. Second, HIV-1 superinfections have been associated with accelerated disease progression, although this is not true for all persons. In fact, superinfections have even been detected in persons controlling their HIV infections without antiretroviral therapy. Third, dual infections can give rise to recombinant viruses, which are increasingly found in the HIV-1 epidemic. Recombinants could have increased fitness over the parental strains, as in vitro models suggest, and could exhibit increased pathogenicity. Multiple drug resistant (MDR) strains could recombine to produce a pan-resistant, transmittable virus.
We will describe in this review what is presently known about super- and re-infection among ambient viral infections, as well as the first cases of HIV-1 superinfection, including HIV-1 triple infections. The clinical implications, the impact of the immune system, and the effect of anti-retroviral therapy will be covered, as will as the timing of HIV superinfection. The methods used to detect HIV-1 dual infections will be discussed in detail. To increase the likelihood of detecting a dual HIV-1 infection, pre-selection of patients can be done by serotyping, heteroduplex mobility assays (HMA), counting the degenerate base codes in the HIV-1 genotyping sequence, or surveying unexpected increases in the viral load during follow-up. The actual demonstration of dual infections involves a great deal of additional research to completely characterize the patient's viral quasispecies. The identification of a source partner would of course confirm the authenticity of the second infection.
doi:10.1186/1742-4690-4-67
PMCID: PMC2045676  PMID: 17892568
11.  Intrapatient Diversity and Its Correlation with Viral Setpoint in Human Immunodeficiency Virus Type 1 CRF02_A/G-IbNG Infection 
Journal of Virology  2002;76(21):10745-10755.
The human immunodeficiency virus type 1 (HIV-1) viral setpoint during the disease-free interval has been strongly associated with future risk of disease progression. An awareness of the correlation between viral setpoint and HIV-1 genetic evolution over time is important in the understanding of viral dynamics and infection. We examined genetic diversity in HIV-1 CRF02_A/G-IbNG-infected seroincident women in Dakar, Senegal; determined whether a viral setpoint kinetic pattern existed for CRF02_A/G-IbNG during the disease-free interval; and correlated viral load level and diversity. Samples were drawn during the disease-free interval from consenting CRF02_A/G-IbNG-infected, antiretroviral therapy-naïve female commercial sex workers in Dakar, Senegal. Based on sequential plasma RNA values, low and high viral setpoint groups were established. Intrapatient diversity and divergence over time was determined from earlier and later time point DNA samples from each person. Most individuals followed the viral setpoint paradigm. For each 1|−|log10 copy/ml of plasma increase in viral load, intrapatient diversity increased by 1.4% (P = 0.028). A greater diversification rate was observed in the high viral setpoint group than in the low viral setpoint group (P = 0.01). Greater nucleotide (P = 0.015) and amino acid (P = 0.048) divergences and a greater nucleotide divergence rate (P = 0.03) were found in the high viral setpoint group. There was no difference between the groups in the ratio of the number of nonsynonymous substitutions per nonsynonymous site to the number of synonymous substitutions per synonymous site. The greater intrapatient diversity, divergence, and diversification rates observed in the high viral setpoint group supports the notion that diversity is driven by cycles of viral replication resulting in accumulated mutations. Recognizing diversity potential based on viral load levels in individuals may inform the design of vaccines and therapies.
doi:10.1128/JVI.76.21.10745-10755.2002
PMCID: PMC136616  PMID: 12368317
12.  Episodic Sexual Transmission of HIV Revealed by Molecular Phylodynamics 
PLoS Medicine  2008;5(3):e50.
Background
The structure of sexual contact networks plays a key role in the epidemiology of sexually transmitted infections, and their reconstruction from interview data has provided valuable insights into the spread of infection. For HIV, the long period of infectivity has made the interpretation of contact networks more difficult, and major discrepancies have been observed between the contact network and the transmission network revealed by viral phylogenetics. The high rate of HIV evolution in principle allows for detailed reconstruction of links between virus from different individuals, but often sampling has been too sparse to describe the structure of the transmission network. The aim of this study was to analyze a high-density sample of an HIV-infected population using recently developed techniques in phylogenetics to infer the short-term dynamics of the epidemic among men who have sex with men (MSM).
Methods and Findings
Sequences of the protease and reverse transcriptase coding regions from 2,126 patients, predominantly MSM, from London were compared: 402 of these showed a close match to at least one other subtype B sequence. Nine large clusters were identified on the basis of genetic distance; all were confirmed by Bayesian Monte Carlo Markov chain (MCMC) phylogenetic analysis. Overall, 25% of individuals with a close match with one sequence are linked to 10 or more others. Dated phylogenies of the clusters using a relaxed clock indicated that 65% of the transmissions within clusters took place between 1995 and 2000, and 25% occurred within 6 mo after infection. The likelihood that not all members of the clusters have been identified renders the latter observation conservative.
Conclusions
Reconstruction of the HIV transmission network using a dated phylogeny approach has revealed the HIV epidemic among MSM in London to have been episodic, with evidence of multiple clusters of transmissions dating to the late 1990s, a period when HIV prevalence is known to have doubled in this population. The quantitative description of the transmission dynamics among MSM will be important for parameterization of epidemiological models and in designing intervention strategies.
Using viral genotype data from HIV drug resistance testing at a London clinic, Andrew Leigh Brown and colleagues derive the structure of the transmission network through phylogenetic analysis.
Editors' Summary
Background.
Human immunodeficiency virus (HIV), the cause of acquired immunodeficiency syndrome (AIDS), is mainly spread through unprotected sex with an infected partner. Like other sexually transmitted diseases, HIV/AIDS spreads through networks of sexual contacts. The characteristics of these complex networks (which include people who have serial sexual relationships with single partners and people who have concurrent sexual relationships with several partners) affect how quickly diseases spread in the short term and how common the disease is in the long term. For many sexually transmitted diseases, sexual contact networks can be reconstructed from interview data. The information gained in this way can be used for partner notification so that transmitters of the disease and people who may have been unknowingly infected can be identified, treated, and advised about disease prevention. It can also be used to develop effective community-based prevention strategies.
Why Was This Study Done?
Although sexual contact networks have provided valuable information about the spread of many sexually transmitted diseases, they cannot easily be used to understand HIV transmission patterns. This is because the period of infectivity with HIV is long and the risk of infection from a single sexual contact with an infected person is low. Another way to understand the spread of HIV is through phylogenetics, which examines the genetic relatedness of viruses obtained from different individuals. Frequent small changes in the genetic blueprint of HIV allow the virus to avoid the human immune response and to become resistant to antiretroviral drugs. In this study, the researchers use recently developed analytical methods, viral sequences from a large proportion of a specific HIV-infected population, and information on when each sample was taken, to learn about transmission of HIV/AIDS in London among men who have sex with men (MSM; a term that encompasses gay, bisexual, and transgendered men and heterosexual men who sometimes have sex with men). This new approach, which combines information on viral genetic variation and viral population dynamics, is called “molecular phylodynamics.”
What Did the Researchers Do and Find?
The researchers compared the sequences of the genes encoding the HIV-1 protease and reverse transcriptase from more than 2,000 patients, mainly MSM, attending a large London HIV clinic between 1997 and 2003. 402 of these sequences closely matched at least one other subtype B sequence (the HIV/AIDS epidemic among MSM in the UK primarily involves HIV subtype B). Further analysis showed that the patients from whom this subset of sequences came formed six clusters of ten or more individuals, as well as many smaller clusters, based on the genetic relatedness of their HIV viruses. The researchers then used information on the date when each sample was collected and a “relaxed clock” approach (which accounts for the possibility that different sequences evolve at different rates) to determine dated phylogenies (patterns of genetic relatedness that indicate when gene sequences change) for the clusters. These phylogenies indicated that at least in one in four transmissions between the individuals in the large clusters occurred within 6 months of infection, and that most of the transmissions within each cluster occurred over periods of 3–4 years during the late 1990s.
What Do These Findings Mean?
This phylodynamic reconstruction of the HIV transmission network among MSM in a London clinic indicates that the HIV epidemic in this population has been episodic with multiple clusters of transmission occurring during the late 1990s, a time when the number of HIV infections in this population doubled. It also suggests that transmission of the virus during the early stages of HIV infection is likely to be an important driver of the epidemic. Whether these results apply more generally to the MSM population at risk for transmitting or acquiring HIV depends on whether the patients in this study are representative of that group. Additional studies are needed to determine this, but if the patterns revealed here are generalizable, then this quantitative description of HIV transmission dynamics should help in the design of strategies to strengthen HIV prevention among MSM.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050050.
Read a related PLoS Medicine Perspective article
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
HIV InSite has comprehensive information on all aspects of HIV/AIDS, including a list of organizations that provide information for gay men and MSM
The US Centers for Disease Control and Prevention provides information on HIV/AIDS and on HIV/AIDS among MSM (in English and Spanish)
Information is available from Avert, an international AIDS charity, on HIV, AIDS, and men who have sex with men
The Center for AIDS Prevention Studies (University of California, San Francisco) provides information on sexual networks and HIV prevention
The US National Center for Biotechnology Information provides a science primer on molecular phylogenetics
UK Collaborative Group on HIV Drug Resistance maintains a database of resistance tests
HIV i-Base offers HIV treatment information for health-care professionals and HIV-positive people
The NIH-funded HIV Sequence Database contains data on genetic sequences, resistance, immunology, and vaccine trials
doi:10.1371/journal.pmed.0050050
PMCID: PMC2267814  PMID: 18351795
13.  Gender Differences in Survival among Adult Patients Starting Antiretroviral Therapy in South Africa: A Multicentre Cohort Study 
PLoS Medicine  2012;9(9):e1001304.
Morna Cornell and colleagues investigate differences in mortality for HIV-positive men and women on antiretroviral therapy in South Africa.
Background
Increased mortality among men on antiretroviral therapy (ART) has been documented but remains poorly understood. We examined the magnitude of and risk factors for gender differences in mortality on ART.
Methods and Findings
Analyses included 46,201 ART-naïve adults starting ART between January 2002 and December 2009 in eight ART programmes across South Africa (SA). Patients were followed from initiation of ART to outcome or analysis closure. The primary outcome was mortality; secondary outcomes were loss to follow-up (LTF), virologic suppression, and CD4+ cell count responses. Survival analyses were used to examine the hazard of death on ART by gender. Sensitivity analyses were limited to patients who were virologically suppressed and patients whose CD4+ cell count reached >200 cells/µl. We compared gender differences in mortality among HIV+ patients on ART with mortality in an age-standardised HIV-negative population.
Among 46,201 adults (65% female, median age 35 years), during 77,578 person-years of follow-up, men had lower median CD4+ cell counts than women (85 versus 110 cells/µl, p<0.001), were more likely to be classified WHO stage III/IV (86 versus 77%, p<0.001), and had higher mortality in crude (8.5 versus 5.7 deaths/100 person-years, p<0.001) and adjusted analyses (adjusted hazard ratio [AHR] 1.31, 95% CI 1.22–1.41). After 36 months on ART, men were more likely than women to be truly LTF (AHR 1.20, 95% CI 1.12–1.28) but not to die after LTF (AHR 1.04, 95% CI 0.86–1.25). Findings were consistent across all eight programmes. Virologic suppression was similar by gender; women had slightly better immunologic responses than men. Notably, the observed gender differences in mortality on ART were smaller than gender differences in age-standardised death rates in the HIV-negative South African population. Over time, non-HIV mortality appeared to account for an increasing proportion of observed mortality. The analysis was limited by missing data on baseline HIV disease characteristics, and we did not observe directly mortality in HIV-negative populations where the participating cohorts were located.
Conclusions
HIV-infected men have higher mortality on ART than women in South African programmes, but these differences are only partly explained by more advanced HIV disease at the time of ART initiation, differential LTF and subsequent mortality, and differences in responses to treatment. The observed differences in mortality on ART may be best explained by background differences in mortality between men and women in the South African population unrelated to the HIV/AIDS epidemic.
Please see later in the article for the Editors' Summary.
Editors' Summary
Background
About 34 million people (most living in low- and middle-income countries) are currently infected with HIV, the virus that causes AIDS. HIV destroys CD4 lymphocytes and other immune system cells, leaving infected individuals susceptible to other infections. Early in the AIDS epidemic, most HIV-infected people died within 10 years of becoming infected. Then, in 1996, antiretroviral therapy (ART)—cocktails of drugs that keep HIV in check—became available. For people living in affluent countries, HIV/AIDS became a chronic condition. However, ART was expensive and, for people living in poorer countries, HIV/AIDS remained a fatal illness. In 2003, this situation was declared a global emergency, and governments and international agencies began to implement plans to increase ART coverage in resource-limited countries. Since then, ART programs in these countries have grown rapidly. In South Africa, for example, about 52% of the 3.14 million adults in need of ART were receiving an ART regimen recommended by the World Health Organization by the end of 2010.
Why Was This Study Done?
The outcomes of ART programs in resource-limited countries need to be evaluated thoroughly so that these programs can be optimized. One area of concern to ART providers is that of gender differences in survival among patients receiving treatment. In sub-Saharan Africa, for example, men are more likely to die than women while receiving ART. This gender difference in mortality may arise because men initiating ART in many African ART programs have more advanced HIV disease than women (early ART initiation is associated with better outcomes than late initiation) or because men are more likely to be lost to follow-up than women (failure to continue treatment is associated with death). Other possible explanations for gender differentials in mortality on ART include gender differences in immunologic and virologic responses to treatment (increased numbers of immune system cells and reduced amounts of virus in the blood, respectively). In this multicenter cohort study, the researchers examine the size of, and risk factors for, gender differences in mortality on ART in South Africa by examining data collected from adults starting ART at International Epidemiologic Databases to Evaluate AIDS South Africa (IeDEA-SA) collaboration sites.
What Did the Researchers Do and Find?
The researchers analyzed data collected from 46,201 ART-naïve adults who started ART between 2002 and 2009 in eight IeDEA-SA ART programs. At ART initiation, men had a lower CD4 count on average and were more likely to have advanced HIV disease than women. During the study, after allowing for factors likely to affect mortality such as HIV disease stage at initiation, men on ART had a 31% higher risk of dying than women. Men were more likely to be lost to follow-up than women, but men and women who were lost to follow-up were equally likely to die. Women had a slightly better immunological response to ART than men but virologic suppression was similar in both genders. Importantly, in analyses of mortality limited to individuals who were virologically suppressed at 12 months and to patients who had a good immunological response to ART, men still had a higher risk of death than women. However, the gender differences in mortality on ART were smaller than the gender differences in age-standardized mortality in the HIV-negative South African population.
What Do These Findings Mean?
These analyses show that among South African patients initiating ART between 2002 and 2009, men were more likely to die than women but that this gender difference in mortality on ART cannot be completely explained by gender differences in baseline characteristics, loss to follow-up, or virologic and/or immunologic responses. Instead, the observed gender differences in mortality can best be explained by background gender differences in mortality in the whole South African population. Because substantial amounts of data were missing in this study (for example, HIV disease stage was not available for all the patients), these findings need to be interpreted cautiously. Moreover, similar studies need to be done in other settings to investigate whether they are generalizable to the South African national ART program and to other countries. If confirmed, however, these findings suggest that the root causes of gender differences in mortality on ART may be unrelated to HIV/AIDS or to the characteristics of ART programs.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001304.
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
Information on the treatment of HIV/AIDS in South Africa is available from the Southern African HIV Clinicians Society
NAM/aidsmap provides basic information about HIV/AIDS and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity on many aspects of HIV/AIDS, including information on HIV/AIDS treatment and care, and on HIV/AIDS in South Africa (in English and Spanish)
WHO provides information about universal access to AIDS treatment (in several languages); its 2010 ART guidelines can be downloaded
Information about the IeDEA-SA collaboration is available
The Treatment Action Campaign provides information on antiretroviral therapy and South African HIV statistics
Patient stories about living with HIV/AIDS are available through Avert; the nonprofit website Healthtalkonline also provides personal stories about living with HIV, including stories about taking anti-HIV drugs and the challenges of anti-HIV drugs
doi:10.1371/journal.pmed.1001304
PMCID: PMC3433409  PMID: 22973181
14.  Public-Health and Individual Approaches to Antiretroviral Therapy: Township South Africa and Switzerland Compared 
PLoS Medicine  2008;5(7):e148.
Background
The provision of highly active antiretroviral therapy (HAART) in resource-limited settings follows a public health approach, which is characterised by a limited number of regimens and the standardisation of clinical and laboratory monitoring. In industrialized countries doctors prescribe from the full range of available antiretroviral drugs, supported by resistance testing and frequent laboratory monitoring. We compared virologic response, changes to first-line regimens, and mortality in HIV-infected patients starting HAART in South Africa and Switzerland.
Methods and Findings
We analysed data from the Swiss HIV Cohort Study and two HAART programmes in townships of Cape Town, South Africa. We included treatment-naïve patients aged 16 y or older who had started treatment with at least three drugs since 2001, and excluded intravenous drug users. Data from a total of 2,348 patients from South Africa and 1,016 patients from the Swiss HIV Cohort Study were analysed. Median baseline CD4+ T cell counts were 80 cells/μl in South Africa and 204 cells/μl in Switzerland. In South Africa, patients started with one of four first-line regimens, which was subsequently changed in 514 patients (22%). In Switzerland, 36 first-line regimens were used initially, and these were changed in 539 patients (53%). In most patients HIV-1 RNA was suppressed to 500 copies/ml or less within one year: 96% (95% confidence interval [CI] 95%–97%) in South Africa and 96% (94%–97%) in Switzerland, and 26% (22%–29%) and 27% (24%–31%), respectively, developed viral rebound within two years. Mortality was higher in South Africa than in Switzerland during the first months of HAART: adjusted hazard ratios were 5.90 (95% CI 1.81–19.2) during months 1–3 and 1.77 (0.90–3.50) during months 4–24.
Conclusions
Compared to the highly individualised approach in Switzerland, programmatic HAART in South Africa resulted in similar virologic outcomes, with relatively few changes to initial regimens. Further innovation and resources are required in South Africa to both achieve more timely access to HAART and improve the prognosis of patients who start HAART with advanced disease.
Comparing HIV treatment in Switzerland, where drug selection is individualized, and South Africa, where a programmatic approach is used, Matthias Egger and colleagues find similar virologic outcomes over two years.
Editors' Summary
Background.
Acquired immunodeficiency syndrome (AIDS) has killed more than 25 million people since the first reported case in 1981, and more than 30 million people are now infected with the human immunodeficiency virus (HIV), which causes AIDS. HIV destroys immune system cells (including CD4 cells, a type of lymphocyte), leaving infected individuals susceptible to other infections. Early in the AIDS epidemic, most HIV-infected people died within 10 years of becoming infected. Then, in 1996, highly active antiretroviral therapy (HAART)—a combination of several antiretroviral drugs—was developed. Now, in resource-rich countries, clinicians provide individually tailored care for HIV-infected people by prescribing combinations of antiretroviral drugs chosen from more than 20 approved medicines. The approach to treatment of HIV in developed countries typically also includes frequent monitoring of the amount of virus in patients' blood (viral load), viral resistance testing (to see whether any viruses are resistant to specific antiretroviral drugs), and regular CD4 cell counts (an indication of immune-system health). Since the implementation of these interventions, the health and life expectancy of people with HIV has improved dramatically in these countries.
Why Was This Study Done?
The history of HIV care in resource-poor countries has been very different. Initially, these countries could not afford to provide HAART for their populations. In 2003, however, governments, international agencies, and funding bodies began to implement plans to increase HAART coverage in developing countries. By December 2006, more than a quarter of the HIV-infected people in low- and middle-income countries who urgently needed treatment were receiving HAART. However, instead of individualized treatment, HAART programs in developing countries follow a public-health approach developed by the World Health Organization. That is, drug regimens, clinical decision-making, and clinical and laboratory monitoring are all standardized. This public-health approach takes into account the realities of under-resourced health systems, but is it as effective as the individualized approach? The researchers addressed this question by comparing virologic responses (the effect of treatment on the viral load), changes to first-line (initial) therapy, and deaths in patients receiving HAART in South Africa (public-health approach) and in Switzerland (individualized approach).
What Did the Researchers Do and Find?
The researchers analyzed data collected since 2001 from more than 2,000 patients enrolled in HAART programs in two townships (Gugulethu and Khayelitsha) in Cape Town, South Africa, and from more than 1,000 patients enrolled in the Swiss HIV Cohort Study, a nationwide study of HIV-infected people. The patients in South Africa, who had a lower starting CD4 cell count and were more likely to have advanced AIDS than the patients in Switzerland, started their treatment for HIV infection with one of four first-line therapies, and about a quarter changed to a second-line therapy during the study. By contrast, 36 first-line regimens were used in Switzerland and half the patients changed to a different regimen. Despite these differences, the viral load was greatly reduced within a year in virtually all the patients and viral rebound (an increased viral load after a low measurement) developed within 2 years in a quarter of the patients in both countries. However, more patients died in South Africa than in Switzerland, particularly during the first 3 months of therapy.
What Do These Findings Mean?
These findings suggest that the public-health approach to HAART practiced in South Africa is as effective in terms of virologic outcomes as the individualized approach practiced in Switzerland. This is reassuring because it suggests that “antiretroviral anarchy” (the unregulated use of antiretroviral drugs, interruptions in drug supplies, and the lack of treatment monitoring), which is likely to lead to the emergence of viral resistance, is not happening in South Africa as some experts feared it might. Thus, these findings support the continued rollout of the public-health approach to HAART in resource-poor countries. Conversely, they also suggest that a more standardized approach to HAART could be taken in Switzerland (and in other industrialized countries) without compromising its effectiveness. Finally, the higher mortality in South Africa than in Switzerland, which partly reflects the many patients in South Africa in desperate need of HAART and their more advanced disease at the start of therapy, suggests that HIV-infected patients in South Africa and in other resource-limited countries would benefit from earlier initiation of therapy.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050148.
The World Health Organization provides information about universal access to HIV treatment (in several languages) and on its recommendations for a public-health approach to antiretroviral therapy for HIV infection
More details on the Swiss HIV Cohort Study and on the studies in Gugulethu and Khayelitsha are available
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
HIV InSite has comprehensive information on all aspects of HIV/AIDS, including detailed information about antiretroviral therapy and links to treatment guidelines for various countries
Information is available from Avert, an international AIDS charity, on HIV and AIDS around the world and on providing AIDS drug treatment for millions
doi:10.1371/journal.pmed.0050148
PMCID: PMC2443185  PMID: 18613745
15.  HIV Treatment as Prevention: Systematic Comparison of Mathematical Models of the Potential Impact of Antiretroviral Therapy on HIV Incidence in South Africa 
PLoS Medicine  2012;9(7):e1001245.
Background
Many mathematical models have investigated the impact of expanding access to antiretroviral therapy (ART) on new HIV infections. Comparing results and conclusions across models is challenging because models have addressed slightly different questions and have reported different outcome metrics. This study compares the predictions of several mathematical models simulating the same ART intervention programmes to determine the extent to which models agree about the epidemiological impact of expanded ART.
Methods and Findings
Twelve independent mathematical models evaluated a set of standardised ART intervention scenarios in South Africa and reported a common set of outputs. Intervention scenarios systematically varied the CD4 count threshold for treatment eligibility, access to treatment, and programme retention. For a scenario in which 80% of HIV-infected individuals start treatment on average 1 y after their CD4 count drops below 350 cells/µl and 85% remain on treatment after 3 y, the models projected that HIV incidence would be 35% to 54% lower 8 y after the introduction of ART, compared to a counterfactual scenario in which there is no ART. More variation existed in the estimated long-term (38 y) reductions in incidence. The impact of optimistic interventions including immediate ART initiation varied widely across models, maintaining substantial uncertainty about the theoretical prospect for elimination of HIV from the population using ART alone over the next four decades. The number of person-years of ART per infection averted over 8 y ranged between 5.8 and 18.7. Considering the actual scale-up of ART in South Africa, seven models estimated that current HIV incidence is 17% to 32% lower than it would have been in the absence of ART. Differences between model assumptions about CD4 decline and HIV transmissibility over the course of infection explained only a modest amount of the variation in model results.
Conclusions
Mathematical models evaluating the impact of ART vary substantially in structure, complexity, and parameter choices, but all suggest that ART, at high levels of access and with high adherence, has the potential to substantially reduce new HIV infections. There was broad agreement regarding the short-term epidemiologic impact of ambitious treatment scale-up, but more variation in longer term projections and in the efficiency with which treatment can reduce new infections. Differences between model predictions could not be explained by differences in model structure or parameterization that were hypothesized to affect intervention impact.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Following the first reported case of AIDS in 1981, the number of people infected with HIV, the virus that causes AIDS, increased rapidly. In recent years, the number of people becoming newly infected has declined slightly, but the virus continues to spread at unacceptably high levels. In 2010 alone, 2.7 million people became HIV-positive. HIV, which is usually transmitted through unprotected sex, destroys CD4 lymphocytes and other immune system cells, leaving infected individuals susceptible to other infections. Early in the AIDS epidemic, half of HIV-infected people died within eleven years of infection. Then, in 1996, antiretroviral therapy (ART) became available, and, for people living in affluent countries, HIV/AIDS gradually became considered a chronic condition. But because ART was expensive, for people living in developing countries HIV/AIDS remained a fatal condition. Roll-out of ART in developing countries first started in the early 2000s. In 2006, the international community set a target of achieving universal ART coverage by 2010. Although this target has still not been reached, by the end of 2010, 6.6 million of the estimated 15 million people in need of ART in developing countries were receiving ART.
Why Was This Study Done?
Several studies suggest that ART, in addition to reducing illness and death among HIV-positive people, reduces HIV transmission. Consequently, there is interest in expanding the provision of ART as a strategy for reducing the spread of HIV (“HIV treatment as prevention"), particularly in sub-Saharan Africa, where one in 20 adults is HIV-positive. It is important to understand exactly how ART might contribute to averting HIV transmission. Several mathematical models that simulate HIV infection and disease progression have been developed to investigate the impact of expanding access to ART on the incidence of HIV (the number of new infections occurring in a population over a year). But, although all these models predict that increased ART coverage will have epidemiologic (population) benefits, they vary widely in their estimates of the magnitude of these benefits. In this study, the researchers systematically compare the predictions of 12 mathematical models of the HIV epidemic in South Africa, simulating the same ART intervention programs to determine the extent to which different models agree about the impact of expanded ART.
What Did the Researchers Do and Find?
The researchers invited groups who had previously developed mathematical models of the epidemiological impact of expanded access to ART in South Africa to participate in a systematic comparison exercise in which their models were used to simulate ART scale-up scenarios in which the CD4 count threshold for treatment eligibility, access to treatment, and retention on treatment were systematically varied. To exclude variation resulting from different model assumptions about the past and current ART program, it was assumed that ART is introduced into the population in the year 2012, with no treatment provision prior to this, and interventions were evaluated in comparison to an artificial counterfactual scenario in which no treatment is provided. A standard scenario based on the World Health Organization's recommended threshold for initiation of ART, although unrepresentative of current provision in South Africa, was used to compare the models. In this scenario, 80% of HIV-infected individuals received treatment, they started treatment on average a year after their CD4 count dropped below 350 cells per microliter of blood, and 85% remained on treatment after three years. The models predicted that, with a start point of 2012, the HIV incidence would be 35%–54% lower in 2020 and 32%–74% lower in 2050 compared to a counterfactual scenario where there was no ART. Estimates of the number of person-years of ART needed per infection averted (the efficiency with which ART reduced new infections) ranged from 6.3–18.7 and from 4.5–20.2 over the periods 2012–2020 and 2012–2050, respectively. Finally, estimates of the impact of ambitious interventions (for example, immediate treatment of all HIV-positive individuals) varied widely across the models.
What Do These Findings Mean?
Although the mathematical models used in this study had different characteristics, all 12 predict that ART, at high levels of access and adherence, has the potential to reduce new HIV infections. However, although the models broadly agree about the short-term epidemiologic impact of treatment scale-up, their longer-term projections (including whether ART alone can eliminate HIV infection) and their estimates of the efficiency with which ART can reduce new infections vary widely. Importantly, it is possible that all these predictions will be wrong—all the models may have excluded some aspect of HIV transmission that will be found in the future to be crucial. Finally, these findings do not aim to indicate which specific ART interventions should be used to reduce the incidence of HIV. Rather, by comparing the models that are being used to investigate the feasibility of “HIV treatment as prevention," these findings should help modelers and policy-makers think critically about how the assumptions underlying these models affect the models' predictions.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001245.
This study is part of the July 2012 PLoS Medicine Collection, Investigating the Impact of Treatment on New HIV Infections
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity on many aspects of HIV/AIDS, including information on HIV/AIDS treatment and care, on HIV treatment as prevention, and on HIV/AIDS in South Africa (in English and Spanish)
The World Health Organization provides information about universal access to AIDS treatment (in English, French, and Spanish); its 2010 ART guidelines can be downloaded
The HIV Modelling Consortium aims to improve scientific support for decision-making by coordinating mathematical modeling of the HIV epidemic
Patient stories about living with HIV/AIDS are available through Avert; the charity website Healthtalkonline also provides personal stories about living with HIV, including stories about taking anti-HIV drugs and the challenges of anti-HIV drugs
doi:10.1371/journal.pmed.1001245
PMCID: PMC3393664  PMID: 22802730
16.  Safety and efficacy assessment of the HVTN 503/Phambili Study: A double-blind randomized placebo-controlled test-of-concept study of a Clade B-based HIV-1 vaccine in South Africa 
The Lancet infectious diseases  2011;11(7):507-515.
Summary
We report the primary analysis of the safety and efficacy of the MRKad5 gag/pol/nef HIV-1 sub-type B vaccine in South Africa (SA), where the major circulating clade is sub-type C.
Methods
This phase IIb double-blind, randomized test-of-concept study was conducted in sexually active HIV-1 sero-negative participants in SA. The co-primary endpoints were a vaccine-induced reduction in HIV-1 acquisition or viral-load setpoint. These were assessed independently in the modified intent-to-treat (MITT) cohort with two-tailed significance tests stratified by gender. Immunogenicity was assessed by interferon-gamma (IFNγ) ELISPOT in peripheral blood mononuclear cells. Following the lack of efficacy of the MRKAd5 HIV-1 vaccine in the Step study, enrollment and vaccination in this study was halted, treatment unblinding occurred and follow-up continued. This study is registered with the SA National Health Research Database (DOH-27-0207-1539) and ClinicalTrials.gov (NCT00413725).
Results
801 of a scheduled 3000 participants were enrolled, of whom 360 (44.9%) were women, more than half (55.6%) had Ad5 titres > 200, and almost a third (29.3%) of men were circumcised. 62 MITT participants were diagnosed with HIV-1, 34 in the vaccine arm and 28 in the placebo arm, with infection rates of 4.54 and 3.70 per 100 person-years, respectively. There was no evidence of vaccine efficacy (VE); the hazard ratio adjusted for gender was 1.25 (95% CI: 0.76, 2.05). VE did not differ by Ad5 titre, gender, age, HSV-2 status, or circumcision. The geometric mean viral load setpoint was 20,483 copies/ml (N=33) in vaccinees and 34,032 copies/ml (N=28) in placebo recipients (p=0.39). The vaccine elicited IFNγ-secreting T cells recognizing both clade B (89.2%) and C (77.4%) antigens.
Conclusion
The MRKAd5 HIV-1 vaccine did not prevent HIV-1 infection or lower viral-load setpoint however early stopping likely compromised our ability to draw conclusions. The high incidence rates seen in SA highlight the critical need for intensified efforts to develop an efficacious vaccine.
doi:10.1016/S1473-3099(11)70098-6
PMCID: PMC3417349  PMID: 21570355
HIV; HIV vaccine efficacy studies; South Africa
17.  Association of the ANRS-12126 Male Circumcision Project with HIV Levels among Men in a South African Township: Evaluation of Effectiveness using Cross-sectional Surveys 
PLoS Medicine  2013;10(9):e1001509.
Betran Auvert and colleagues report findings from the Bophelo Pele project, a community-based HIV prevention intervention offering free voluntary medical male circumcision (VMMC), that demonstrate an association between VMMC roll-out and a reduction in the incidence and prevalence of HIV in the community.
Please see later in the article for the Editors' Summary
Background
Randomized controlled trials have shown that voluntary medical male circumcision (VMMC) reduces HIV infection by 50% to 60% in sub-Saharan African populations; however, little is known about the population-level effect of adult male circumcision (MC) as an HIV prevention method. We assessed the effectiveness of VMMC roll-out on the levels of HIV in the South African township of Orange Farm where the first randomized controlled trial (RCT) to test the effect of VMMC on HIV acquisition was conducted in 2002–2005.
Methods and Findings
The Bophelo Pele project is a community-based campaign against HIV, which includes the roll-out of free VMMC. A baseline cross-sectional biomedical survey was conducted in 2007–2008 among a random sample of 1,998 men aged 15 to 49 (survey response rate 80.7%). In 2010–2011, we conducted a follow-up random survey among 3,338 men aged 15 to 49 (survey response rate 79.6%) to evaluate the project. Participants were interviewed, blood samples were collected and tested for HIV and recent HIV infection (using the BED HIV incidence assay), and MC status was assessed through a clinical examination. Data were analyzed using multivariate and propensity statistical methods.
Owing to the VMMCs performed in the context of the RCT and the Bophelo Pele project, the prevalence rate of adult MC increased from 0.12 (95% CI 0.10–0.14) to 0.53 (95% CI 0.51–0.55). Without these VMMCs, the HIV prevalence rate in 2010–2011 would have been 19% (95% CI 12%–26%) higher (0.147 instead of 0.123).
When comparing circumcised and uncircumcised men, no association of MC status with sexual behavior was detected. Among circumcised and uncircumcised men, the proportion consistently using condoms with non-spousal partners in the past 12 months was 44.0% (95% CI 41.7%–46.5%) versus 45.4% (95% CI 42.2%–48.6%) with weighted prevalence rate ratio (wPRR) = 0.94 (95% CI 0.85–1.03). The proportion having two or more non-spousal partners was 50.4% (95% CI 47.9%–52.9%) versus 44.2% (95% CI 41.3%–46.9%) with wPRR = 1.03 (95% CI 0.95–1.10).
We found a reduction of BED-estimated HIV incidence rate ranging from 57% (95% CI 29%–76%) to 61% (95% CI 14%–83%) among circumcised men in comparison with uncircumcised men.
Conclusions
Findings suggest that the roll-out of VMMC in Orange Farm is associated with a significant reduction of HIV levels in the community. The main limitation of the study is that it was not randomized and cannot prove a causal association. The roll-out of VMMC among adults in sub-Saharan Africa should be an international priority and needs to be accelerated to effectively combat the spread of HIV.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Every year about 2.2 million people (mostly in sub-Saharan Africa) become infected with HIV, the virus that causes AIDS. There is no cure for HIV/AIDS. Consequently, prevention of HIV transmission is extremely important. Because HIV is most often spread through unprotected sex with an infected partner, individuals can reduce their risk of HIV infection by abstaining from sex, by having only one or a few sexual partners, and by always using a male or female condom. The results of three randomized controlled trials conducted in sub-Saharan Africa also suggest that voluntary medical male circumcision (VMMC)—the removal of the foreskin, a loose fold of skin that covers the head of the penis—can reduce the heterosexual acquisition of HIV in men by 50%–60%. In 2007, the World Health Organization (WHO) and the Joint United Nations Programme on HIV/AIDS (UNAIDS) recommended that VMMC should be offered as part of comprehensive HIV risk reduction programs in settings with generalized HIV epidemics and low levels of male circumcision and prioritized 14 east and southern African countries for VMMC roll-out.
Why Was This Study Done?
To date, about 3 million VMMCs have been performed for HIV prevention but it is not known whether “real world” VMMC roll-out programs will replicate the promising results obtained in the earlier trials. Indeed, there are fears that “risk compensation” (an increase in risky sexual behaviors after VMMC) might lead to increased HIV transmission in regions where VMMC is rolled out. In this study, the researchers use sequential cross-sectional surveys (studies that collect data from a group of people at a single time point) to investigate HIV infection levels in men in Orange Farm, a township in South Africa where one of the randomized controlled trials of VMMC was undertaken. The surveys were conducted before and after implementation of the Bophelo Pele project, a community-based campaign against HIV that was initiated in 2008 and that includes free VMMC.
What Did the Researchers Do and Find?
The researchers asked a random sample of nearly 2,000 men aged 15–49 years about their sexual behavior (for example, how many non-spousal partners they had had over the past year), and their intention to become circumcised if uncircumcised in a baseline survey in 2007–2008. The study participants were also offered HIV counseling and testing (including a test that indicated whether the participant had recently become HIV positive) and were examined to see whether they were already circumcised. A similar follow-up survey was conducted in 2010–2011 in which more than 3,000 men were invited to take part. At baseline, 12% of the men surveyed had been circumcised (a prevalence of circumcision of 12%) whereas in the follow-up survey, the overall prevalence of circumcision and the prevalence of circumcision among 15–29 year-olds (an important target group for VMMC roll-out) were 53% and 58%, respectively. The overall HIV prevalence at follow-up was 12% and the researchers estimated that without the VMMCs performed during the Bophelo Pele project and the preceding randomized control trial the prevalence of HIV among men living in Orange Farm would have been 15% in 2011. Using various cut-off values and corrections for a laboratory-based test to measure recent HIV infections, the researchers reported a reduction in the rate of new HIV infections (incidence rate) ranging from 57% to 61% among circumcised men in comparison with uncircumcised men. Importantly, there was no evidence of an association between circumcision status and risky sexual behavior but circumcision was associated with a reduction in the number of men who had recently become HIV positive.
What Do These Findings Mean?
These findings suggest that VMMC roll out in Orange Farm is associated with a reduction in HIV infection levels in the community and that circumcision is not associated with changes in sexual behavior that might affect HIV infection rates. They also suggest that VMMC roll-out is associated with a rapid uptake of VMMC, especially among young men, in an African community where male circumcision is not a social norm. Because this study is not a randomized controlled trial, it cannot establish cause and effect. Thus, although the observed reduction in HIV prevalence among circumcised men compared to uncircumcised men suggests that circumcision provided protection against HIV acquisition within the study population, the results do not conclusively prove this. The findings of this study nevertheless support the continuation and acceleration of the roll-out of adult VMMC in Africa although further studies are needed to show whether VMMC roll-out is also associated with a reduction in HIV acquisition among women and among uncircumcised men.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001509.
Information and resources on male circumcision for HIV prevention are available
Information is available from the US National Institute of Allergy and infectious diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS, summaries of recent research findings on HIV care and treatment, and information on male circumcision for the prevention of HIV transmission
Information is available from WHO and UNAIDS on all aspects of HIV/AIDS; the Clearinghouse on Male Circumcision, a resource provided by WHO, UNAIDS and other international bodies, provides information and tools for VMMC policy development and program implementation; a report entitled Progress in scaling up voluntary medical male circumcision for HIV prevention in East and Southern Africa, January-December 2011 is available
Information is available from Avert, an international AIDS charity on many aspects of HIV/AIDS, including information on HIV and AIDS in South Africa, on HIV prevention, and on circumcision and HIV (in English and Spanish)
A 2010 PLOS Medicine Research Article by Pascale Lissouba et al. provides more information about the Bophelo Pele project
Personal stories about living with HIV/AIDS are available through Avert, through Nam/aidsmap, and through the charity website Healthtalkonline; a personal story about circumcision in Zimbabwe is available
doi:10.1371/journal.pmed.1001509
PMCID: PMC3760784  PMID: 24019763
18.  Kidney and liver organ transplantation in persons with human immunodeficiency virus 
Executive Summary
Objective
The objective of this analysis is to determine the effectiveness of solid organ transplantation in persons with end stage organ failure (ESOF) and human immunodeficiency virus (HIV+)
Clinical Need: Condition and Target Population
Patients with end stage organ failure who have been unresponsive to other forms of treatment eventually require solid organ transplantation. Similar to persons who are HIV negative (HIV−), persons living with HIV infection (HIV+) are at risk for ESOF from viral (e.g. hepatitis B and C) and non-viral aetiologies (e.g. coronary artery disease, diabetes, hepatocellular carcinoma). Additionally, HIV+ persons also incur risks of ESOF from HIV-associated nephropathy (HIVAN), accelerated liver damage from hepatitis C virus (HCV+), with which an estimated 30% of HIV positive (HIV+) persons are co-infected, and coronary artery disease secondary to antiretroviral therapy. Concerns that the need for post transplant immunosuppression and/or the interaction of immunosuppressive drugs with antiretroviral agents may accelerate the progression of HIV disease, as well as the risk of opportunistic infections post transplantation, have led to uncertainty regarding the overall benefit of transplantation among HIV+ patients. Moreover, the scarcity of donor organs and their use in a population where the clinical benefit of transplantation is uncertain has limited the availability of organ transplantation to persons living with ESOF and HIV.
With the development of highly active anti retroviral therapy (HAART), which has been available in Canada since 1997, there has been improved survival and health-related quality of life for persons living with HIV. HAART can suppress HIV replication, enhance immune function, and slow disease progression. HAART managed persons can now be expected to live longer than those in the pre-HAART era and as a result many will now experience ESOF well before they experience life-threatening conditions related to HIV infection. Given their improved prognosis and the burden of illness they may experience from ESOF, the benefit of solid organ transplantation for HIV+ patients needs to be reassessed.
Evidence-Based Analysis Methods
Research Questions
What are the effectiveness and cost effectiveness of solid organ transplantation in HIV+ persons with ESOF?
Literature Search
A literature search was performed on September 22, 2009 using OVID MEDLINE, MEDLINE In-Process and Other Non-Indexed Citations, EMBASE, the Cumulative Index to Nursing & Allied Health Literature (CINAHL), the Cochrane Library, and the International Agency for Health Technology Assessment (INAHTA) for studies published from January 1, 1996 to September 22, 2009.
Inclusion Criteria
Systematic review with or without a Meta analysis, RCT, Non-RCT with controls
HIV+ population undergoing solid organ transplantation
HIV+ population managed with HAART therapy
Controls include persons undergoing solid organ transplantation who are i) HIV− ii) HCV+ mono-infected, and iii) HIV+ persons with ESOF not transplanted.
Studies that completed and reported results of a Kaplan-Meier Survival Curve analysis.
Studies with a minimum (mean or medium) follow up of 1-year.
English language citations
Exclusion Criteria
Case reports and case series were excluded form this review.
Outcomes of Interest
i) Risk of Death after transplantation
ii) Death censored graft survival (DCGS)
iii) HIV disease progression defined as the post transplant incidence of:
- opportunistic infections or neoplasms,
- CD4+ T-cell count < 200mm3, and
- any detectable level of plasma HIV viral load.
iv) Acute graft rejection,
v) Return to dialysis,
vi) Recurrence of HCV infection
Summary of Findings
No direct evidence comparing an HIV+ cohort undergoing transplantation with the same not undergoing transplantation (wait list) was found in the literature search.
The results of this review are reported for the following comparison cohorts undergoing transplantation:
i) Kidney Transplantation: HIV+ cohort compared with HIV− cohort
ii) Liver Transplantation: HIV+ cohort compared with HIV− negative cohort
iii) Liver Transplantation: HIV+ HCV+ (co-infected) cohort compared with HCV+ (mono-infected) cohort
Kidney Transplantation: HIV+ vs. HIV−
Based on a pooled HIV+ cohort sample size of 285 patients across four studies, the risk of death after kidney transplantation in an HIV+ cohort does not differ to that of an HIV− cohort [hazard ratio (HR): 0.90; 95% CI: 0.36, 2.23]. The quality of evidence supporting this outcome is very low.
Death censored graft survival was reported in one study with an HIV+ cohort sample size of 100, and was statistically significantly different (p=.03) to that in the HIV− cohort (n=36,492). However, the quality of evidence supporting this outcome was determined to be very low. There was also uncertainty in the rate of return to dialysis after kidney transplantation in both the HIV+ and HIV− groups and the effect, if any, this may have on patient survival. Because of the very low quality evidence rating, the effect of kidney transplantation on HIV-disease progression is uncertain.
The rate of acute graft rejection was determined using the data from one study. There was a nonsignificant difference between the HIV+ and HIV− cohorts (OR 0.13; 95% CI: 0.01, 2.64), although again, because of very low quality evidence there is uncertainty in this estimate of effect.
Liver Transplantation: HIV+ vs. HIV−
Based on a combined HIV+ cohort sample size of 198 patient across five studies, the risk of death after liver transplantation in an HIV+ cohort (with at least 50% of the cohort co-infected with HCV+) is statistically significantly 64% greater compared with an HIV− cohort (HR: 1.64; 95% CI: 1.32, 2.02). The quality of evidence supporting this outcome is very low.
Death censored graft survival was reported for an HIV+ cohort in one study (n=11) however the DCGS rate of the contemporaneous control HIV− cohort was not reported. Because of sparse data the quality of evidence supporting this outcome is very low indicating death censored graft survival is uncertain.
Both the CD4+ T-cell count and HIV viral load appear controlled post transplant with an incidence of opportunistic infection of 20.5%. However, the quality of this evidence for these outcomes is very low indicating uncertainty in these effects. Similarly, because of very low quality evidence there is uncertainty in the rate of acute graft rejection among both the HIV+ and HIV− groups
Liver Transplantation: HIV+/HCV+ vs. HCV+
Based on a combined HIV+/HCV+ cohort sample size of 156 from seven studies, the risk of death after liver transplantation is significantly greater (2.8 fold) in a co-infected cohort compared with an HCV+ mono-infected cohort (HR: 2.81; 95% CI: 1.47, 5.37). The quality of evidence supporting this outcome is very low. Death censored graft survival evidence was not available.
Regarding disease progression, based on a combined sample size of 71 persons in the co-infected cohort, the CD4+ T-cell count and HIV viral load appear controlled post transplant; however, again the quality of evidence supporting this outcome is very low. The rate of opportunistic infection in the co-infected cohort was 7.2%. The quality of evidence supporting this estimate is very low, indicating uncertainty in these estimates of effect.
Based on a combined HIV+/HCV+ cohort (n=57) the rate of acute graft rejection does not differ to that of an HCV+ mono-infected cohort (OR: 0.88; 95% CI: 0.44, 1.76). Also based on a combined HIV+/HCV+ cohort (n=83), the rate of HCV+ recurrence does not differ to that of an HCV+ mono-infected cohort (OR: 0.66; 95% CI: 0.27, 1.59). In both cases, the quality of the supporting evidence was very low.
Overall, because of very low quality evidence there is uncertainty in the effect of kidney or liver transplantation in HIV+ persons with end stage organ failure compared with those not infected with HIV. Examining the economics of this issue, the cost of kidney and liver transplants in an HIV+ patient population are, on average, 56K and 147K per case, based on both Canadian and American experiences.
PMCID: PMC3377507  PMID: 23074407
19.  Cost-Effectiveness of Male Circumcision for HIV Prevention in a South African Setting  
PLoS Medicine  2006;3(12):e517.
Background
Consistent with observational studies, a randomized controlled intervention trial of adult male circumcision (MC) conducted in the general population in Orange Farm (OF) (Gauteng Province, South Africa) demonstrated a protective effect against HIV acquisition of 60%. The objective of this study is to present the first cost-effectiveness analysis of the use of MC as an intervention to reduce the spread of HIV in sub-Saharan Africa.
Methods and Findings
Cost-effectiveness was modeled for 1,000 MCs done within a general adult male population. Intervention costs included performing MC and treatment of adverse events. HIV prevalence was estimated from published estimates and incidence among susceptible subjects calculated assuming a steady-state epidemic. Effectiveness was defined as the number of HIV infections averted (HIA), which was estimated by dynamically projecting over 20 years the reduction in HIV incidence observed in the OF trial, including secondary transmission to women. Net savings were calculated with adjustment for the averted lifetime duration cost of HIV treatment. Sensitivity analyses examined the effects of input uncertainty and program coverage. All results were discounted to the present at 3% per year.
For Gauteng Province, assuming full coverage of the MC intervention, with a 2005 adult male prevalence of 25.6%, 1,000 circumcisions would avert an estimated 308 (80% CI 189–428) infections over 20 years. The cost is $181 (80% CI $117–$306) per HIA, and net savings are $2.4 million (80% CI $1.3 million to $3.6 million). Cost-effectiveness is sensitive to the costs of MC and of averted HIV treatment, the protective effect of MC, and HIV prevalence. With an HIV prevalence of 8.4%, the cost per HIA is $551 (80% CI $344–$1,071) and net savings are $753,000 (80% CI $0.3 million to $1.2 million). Cost-effectiveness improves by less than 10% when MC intervention coverage is 50% of full coverage.
Conclusions
In settings in sub-Saharan Africa with high or moderate HIV prevalence among the general population, adult MC is likely to be a cost-effective HIV prevention strategy, even when it has a low coverage. MC generates large net savings after adjustment for averted HIV medical costs.
Based on data from a trial of adult male circumcision to reduce the spread of HIV, a modeling study shows this intervention to be a cost-effective strategy.
Editors' Summary
Background.
Preventing the spread of HIV is an enormous challenge of great importance worldwide. In 2005, HIV/AIDS was responsible for around 3 million deaths, of which approximately one-third were in sub-Saharan Africa. HIV is spread from one person to another in three main ways: through unprotected sex; through contaminated blood or blood products (for example when shared needles are used); and from mother to child (during pregnancy, labor, and breastfeeding). Many strategies for preventing HIV focus on reducing risky behaviors. For example, condoms used correctly are effective at preventing HIV infection, and many countries now aim to promote condom use, together with other approaches that will reduce the risk of getting HIV. However, it is unlikely that strategies involving large-scale changes in behavior will ever be completely effective. Recently, much attention has focused on the possibility that circumcision might provide men with some protection against getting HIV. The results of a trial carried out in South Africa, the ANRS 1265 trial (published in PLoS Medicine in October 2005) seem to support this theory, and additional trials are being carried out in Kenya and Uganda. The results from these further trials will help determine whether, and to what extent, the effect of circumcision seen in the South African trial is true more generally.
Why Was This Study Done?
The investigators who had carried out the South African circumcision trial wanted to find out how the economic aspects of this prevention strategy would compare with other strategies for prevention of HIV. Specifically, they wanted to know how much male circumcision would cost overall, per HIV infection prevented, as compared with the cost of other strategies. They also wanted to understand whether circumcision would be “cost-saving.” In other words, would the cost of performing the operation (together with the cost of treating any adverse effects suffered by the men who were circumcised) be offset by the costs of treatment for HIV infections that the intervention prevented? Getting this information is crucial before health policy makers can decide what strategies for preventing HIV are most appropriate for their country.
What Did the Researchers Do and Find?
In this study, the researchers carried out a set of mathematical calculations, using the results from the ANRS 1265 trial, together with some other data and background assumptions. Their model was based on a hypothetical group of 1,000 men, all of whom would be circumcised. The researchers calculated that in such a hypothetical group, the cost of providing male circumcision, per HIV infection prevented, would be around $180. Overall, this procedure seemed to be cost-saving when the cost of HIV treatment was also factored in; around $2.4 million would be saved for the 1,000 men circumcised.
What Do These Findings Mean?
These results suggest that, assuming the results of the South African trial are generally true, male circumcision would reduce the cost of health care in South Africa, mainly through savings on the cost of HIV treatment. The overall cost of male circumcision, per HIV infection prevented, is reasonable as compared to the costs of other strategies for prevention of HIV. There would also be implications for HIV prevention programs in other African countries. However, these estimates are based on the data from one trial only. The World Health Organization does not currently recommend the promotion of male circumcision for prevention of HIV. Meanwhile, proven strategies for preventing HIV exist, and more information is available from the links below.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0030517.
The World Health Organization has an HIV/AIDS program site providing comprehensive information on the HIV/AIDS epidemic worldwide
General information and resources from the US Centers for Disease Control and Prevention on preventing HIV/AIDS
Fact sheet from the Joint United Nations Programme on HIV/AIDS about male circumcision and HIV
Results of the ANRS 1265 Trial evaluating male circumcision for HIV prevention were published in PLoS Medicine in October 2005; two related “Perspective” articles were also published in the same issue by Nandi Siegfried and Peter Cleaton-Jones
doi:10.1371/journal.pmed.0030517
PMCID: PMC1716193  PMID: 17194197
20.  Changes in HIV Incidence among People Who Inject Drugs in Taiwan following Introduction of a Harm Reduction Program: A Study of Two Cohorts 
PLoS Medicine  2014;11(4):e1001625.
Kenrad Nelson and colleagues report on the association between HIV incidence and exposure to a national harm-reduction program among people who inject drugs in Taiwan.
Please see later in the article for the Editors' Summary
Background
Harm reduction strategies for combating HIV epidemics among people who inject drugs (PWID) have been implemented in several countries. However, large-scale studies using sensitive measurements of HIV incidence and intervention exposures in defined cohorts are rare. The aim of this study was to determine the association between harm reduction programs and HIV incidence among PWID.
Methods and Findings
The study included two populations. For 3,851 PWID who entered prison between 2004 and 2010 and tested HIV positive upon incarceration, we tested their sera using a BED HIV-1 capture enzyme immunoassay to estimate HIV incidence. Also, we enrolled in a prospective study a cohort of 4,357 individuals who were released from prison via an amnesty on July 16, 2007. We followed them with interviews at intervals of 6–12 mo and by linking several databases. A total of 2,473 participants who were HIV negative in January 2006 had interviews between then and 2010 to evaluate the association between use of harm reduction programs and HIV incidence. We used survival methods with attendance at methadone clinics as a time-varying covariate to measure the association with HIV incidence. We used a Poisson regression model and calculated the HIV incidence rate to evaluate the association between needle/syringe program use and HIV incidence. Among the population of PWID who were imprisoned, the implementation of comprehensive harm reduction programs and a lower mean community HIV viral load were associated with a reduced HIV incidence among PWID. The HIV incidence in this population of PWID decreased from 18.2% in 2005 to 0.3% in 2010. In an individual-level analysis of the amnesty cohort, attendance at methadone clinics was associated with a significantly lower HIV incidence (adjusted hazard ratio: 0.20, 95% CI: 0.06–0.67), and frequent users of needle/syringe program services had lower HIV incidence (0% in high NSP users, 0.5% in non NSP users). In addition, no HIV seroconversions were detected among prison inmates.
Conclusions
Although our data are affected by participation bias, they strongly suggest that comprehensive harm- reduction services and free treatment were associated with reversal of a rapidly emerging epidemic of HIV among PWID.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
About 35 million people worldwide are currently infected with HIV, the virus that causes AIDS, and about 2.3 million people become newly infected every year. HIV is mainly transmitted through unprotected sex with an infected partner. However, people who inject drugs (PWID) have a particularly high risk of HIV infection because blood transfer through needle and syringe sharing can transmit the virus. It is estimated that 5%–10% of all people living with HIV are PWID. Indeed, in some regions of the world the primary route of HIV transmission is through shared drug injection equipment and the prevalence (the proportion of a population that has a specific disease) of HIV infection among PWID is very high. In Asia, for example, more than a quarter of PWID are HIV positive. Because the high prevalence of HIV among PWID poses a global health challenge, bodies such as the Joint United Nations Programme on HIV/AIDS endorse harm reduction strategies to prevent risky injection behaviors among PWID. These strategies include the provision of clean needles and syringes, opioid substitution therapy such as methadone maintenance treatment, and antiretroviral treatment for HIV-positive PWID.
Why Was This Study Done?
Although harm reduction strategies for combating HIV epidemics among PWID have been implemented in several countries, few large-scale studies have examined the association between HIV incidence (the proportion of new cases of HIV in a population per year) and exposure to harm reduction programs among PWID. In this cohort study (an investigation that determines the characteristics of a group of people and then follows them over time), the researchers determine the association between harm reduction programs and HIV incidence among PWID in Taiwan. HIV infections used to be rare among the 60,000 PWID living in Taiwan, but after the introduction of a new HIV strain into the country in 2003, an HIV epidemic spread rapidly. In response, the Taiwanese government introduced a pilot program of harm reduction that included the provision of clean needles and syringes and health education in July 2005. The program was expanded to include methadone maintenance treatment in early 2006 and implemented nationwide in June 2006.
What Did the Researchers Do and Find?
The researchers enrolled two study populations. The first cohort comprised 3,851 PWID who were incarcerated for illicit drug use between 2004 and 2010 and who tested positive for HIV upon admission into prison. By using the BED assay, which indicates whether an HIV infection is recent, the researchers were able to determine the HIV incidence among the prisoners. In 2004, the estimated HIV incidence among prisoners with a history of drug injection was 6.44%. The incidence peaked in 2005 at 18.2%, but fell to 0.3% in 2010.
The second study population comprised 2,473 individuals who were HIV negative on January 1, 2006, and who had been incarcerated for drug use crimes but were released on July 16, 2007, during an amnesty. The researchers regularly interviewed these participants between their release and 2010 about their use of harm reduction interventions, and obtained other data about them (for example, diagnosis of HIV infection) from official databases. Analysis of all these data indicated that, in this cohort, attendance at methadone maintenance treatment clinics and frequent use of needle and syringe services were both associated with a significantly lower HIV incidence.
What Do These Findings Mean?
These findings suggest that the introduction of a comprehensive harm reduction program in Taiwan was associated with a significant reduction in the HIV incidence rate among PWID. These findings must be interpreted with caution, however. First, because the participants in the study were selected from PWID with histories of incarceration, the findings may not be representative of all PWID in Taiwan or of PWID in other countries. Second, PWID who chose to use needle and syringe services or methadone maintenance treatment clinics might have shared other unknown characteristics that affected their risk of HIV infection. Finally, some of the reduction in HIV incidence seen during the study is likely to be associated with the availability of free treatment, which has been offered to all HIV-positive individuals in Taiwan since 1997. Despite these limitations, these findings suggest that countries with a high prevalence and incidence of HIV among PWID should provide comprehensive harm reduction services to their populations to reduce risky drug injection behaviors.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001625.
Information is available from the US National Institute of Allergy and Infectious diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS, and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including information on injecting drug users and HIV/AIDS and on harm reduction and HIV prevention (in English and Spanish)
The US National Institute on Drug Abuse also provides information about drug abuse and HIV/AIDS (in English and Spanish)
The 2013 UNAIDS World AIDS Day report provides up-to-date information about the AIDS epidemic and efforts to halt it
Personal stories about living with HIV/AIDS are available through Avert, Nam/aidsmap, and Healthtalkonline
doi:10.1371/journal.pmed.1001625
PMCID: PMC3979649  PMID: 24714449
21.  Hormonal contraceptive use and HIV disease progression among women in Uganda and Zimbabwe 
Background
HIV-infected women need highly effective contraception to reduce unintended pregnancies and mother-to-child HIV transmission. Previous studies report conflicting results regarding the effect of hormonal contraception (HC) on HIV disease progression.
Methods
HIV-infected women in Uganda and Zimbabwe were recruited immediately after seroconversion; CD4 testing and clinical exams were conducted quarterly. The study endpoint was time to AIDS (two successive CD4 ≤200 cells/mm3 or WHO advanced stage 3 or stage 4 disease). We used marginal structural Cox survival models to estimate the effect of cumulative exposure to depot-medroxyprogesterone acetate (DMPA) and oral contraceptives (OC) on time to AIDS.
Results
303 HIV-infected women contributed 1,408 person-years (py). 111 women (37%) developed AIDS. Cumulative probability of AIDS was 50% at 7 years and did not vary by country. AIDS incidence was 6.6, 9.3 and 8.8 per 100py for DMPA, OC and non-hormonal users. Neither DMPA (adjusted hazard ratio (AHR) = 0.90; 95% CI 0.76-1.08) nor OCs (AHR =1.07; 95% CI 0.89-1.29) were associated with HIV disease progression. Alternative exposure definitions of HC use during the year prior to AIDS or at time of HIV infection produced similar results. STI symptoms were associated with faster progression while young age at HIV infection (18-24 years) was associated with slower progression. Adding baseline CD4 level and setpoint viral load to models did not change the HC results but subtype D infection became associated with disease progression.
Conclusion
Hormonal contraceptive use was not associated with more rapid HIV disease progression but older age, STI symptoms and subtype D infection were.
doi:10.1097/QAI.0b013e318214ba4a
PMCID: PMC3164299  PMID: 21358412
HIV; disease progression; hormonal contraception; family planning; women
22.  HIV among People Who Inject Drugs in the Middle East and North Africa: Systematic Review and Data Synthesis 
PLoS Medicine  2014;11(6):e1001663.
Laith Abu-Raddad and colleagues assess the current state of knowledge of the HIV epidemic among people who inject drugs in the Middle East and North Africa.
Please see later in the article for the Editors' Summary
Background
It is perceived that little is known about the epidemiology of HIV infection among people who inject drugs (PWID) in the Middle East and North Africa (MENA). The primary objective of this study was to assess the status of the HIV epidemic among PWID in MENA by describing HIV prevalence and incidence. Secondary objectives were to describe the risk behavior environment and the HIV epidemic potential among PWID, and to estimate the prevalence of injecting drug use in MENA.
Methods and Findings
This was a systematic review following the PRISMA guidelines and covering 23 MENA countries. PubMed, Embase, regional and international databases, as well as country-level reports were searched up to December 16, 2013. Primary studies reporting (1) the prevalence/incidence of HIV, other sexually transmitted infections, or hepatitis C virus (HCV) among PWIDs; or (2) the prevalence of injecting or sexual risk behaviors, or HIV knowledge among PWID; or (3) the number/proportion of PWID in MENA countries, were eligible for inclusion. The quality, quantity, and geographic coverage of the data were assessed at country level. Risk of bias in predefined quality domains was described to assess the quality of available HIV prevalence measures. After multiple level screening, 192 eligible reports were included in the review. There were 197 HIV prevalence measures on a total of 58,241 PWID extracted from reports, and an additional 226 HIV prevalence measures extracted from the databases.
We estimated that there are 626,000 PWID in MENA (range: 335,000–1,635,000, prevalence of 0.24 per 100 adults). We found evidence of HIV epidemics among PWID in at least one-third of MENA countries, most of which are emerging concentrated epidemics and with HIV prevalence overall in the range of 10%–15%. Some of the epidemics have however already reached considerable levels including some of the highest HIV prevalence among PWID globally (87.1% in Tripoli, Libya). The relatively high prevalence of sharing needles/syringes (18%–28% in the last injection), the low levels of condom use (20%–54% ever condom use), the high levels of having sex with sex workers and of men having sex with men (15%–30% and 2%–10% in the last year, respectively), and of selling sex (5%–29% in the last year), indicate a high injecting and sexual risk environment. The prevalence of HCV (31%–64%) and of sexually transmitted infections suggest high levels of risk behavior indicative of the potential for more and larger HIV epidemics.
Conclusions
Our study identified a large volume of HIV-related biological and behavioral data among PWID in the MENA region. The coverage and quality of the data varied between countries. There is robust evidence for HIV epidemics among PWID in multiple countries, most of which have emerged within the last decade and continue to grow. The lack of sufficient evidence in some MENA countries does not preclude the possibility of hidden epidemics among PWID in these settings. With the HIV epidemic among PWID in overall a relatively early phase, there is a window of opportunity for prevention that should not be missed through the provision of comprehensive programs, including scale-up of harm reduction services and expansion of surveillance systems.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
About 35 million people worldwide are currently infected with HIV, the virus that causes AIDS, and around 2.3 million people become newly infected every year. HIV is mainly transmitted through unprotected sex with an infected partner. However, people who inject drugs (PWID) have a particularly high risk of HIV infection because blood transfer through needle and syringe sharing can transmit the virus. Worldwide, 5%–10% of all HIV-positive people are PWID but in some regions of the world the fraction of all HIV-positive people that are PWID is even higher. To meet the global health challenge of the high HIV prevalence (the proportion of a population that has a specific disease) among PWID, the Joint United Nations Programme on HIV/AIDS (UNAIDS) and other international bodies endorse harm reduction strategies to prevent risky injection behaviors among PWID. These strategies include education and the provision of clean needles, syringes, and opioid substitution therapy.
Why Was This Study Done?
To maximize the effect of these harm-reduction strategies in specific regions, it is important to understand the status of the HIV epidemic among PWID. Although surveillance systems provide the information on HIV infection needed to track the progress of HIV epidemics among PWID in many regions, little is known about the HIV epidemic among PWID in the Middle East and North Africa (MENA, a geographical region that encompasses countries that share historical, socio-cultural, linguistic, and religious characteristics). Several factors contribute to the likelihood of individuals injecting drugs in MENA. For example, Afghanistan (a MENA country) produces most of the world's supply of heroin, which is largely trafficked through Iran and Pakistan (also MENA countries). In this systematic review and data synthesis, the researchers use predefined criteria to identify all the published and unpublished data on HIV prevalence and incidence (the number of new cases of a disease in a population in a given time) among PWID in MENA and combine (synthesize) these data to assess the status of the HIV epidemic in this key population for HIV transmission in MENA.
What Did the Researchers Do and Find?
The researchers identified 192 reports that reported the prevalence/incidence of HIV, other sexually transmitted infections and infection with hepatitis C virus (HCV, another virus transmitted through drug injection) among PWID, the prevalence of injecting or sexual risk behaviors among PWID, or the number/proportion of PWID in MENA. From these data, the researchers estimated that there are about 600,000 PWID in MENA (a prevalence of 0.24 per 100 adults, which is comparable with figures from other regions). The data provided evidence for HIV epidemics among PWID in at least a third of MENA countries, mainly emerging concentrated epidemics (epidemics that are still growing but in which HIV infection and transmission are already considerable). HIV prevalence among PWID in MENA varied considerably, reaching an extremely high prevalence of 87.1% in Tripoli, Libya. The data also revealed a high injecting and sexual risk environment among PWID in MENA (for example, on average, about a quarter of PWID shared a needle or syringe in their most recent injection and only a third reported ever using condoms) that, together with a high prevalence of HCV and sexually transmitted infections among PWID, indicates the potential for more and larger HIV epidemics.
What Do These Findings Mean?
These findings indicate that substantial amounts of HIV-related data have been collected from PWID in MENA but that the coverage and quality of these data vary widely between countries. They provide robust evidence for growing HIV epidemics, most of which have emerged within the past decade, among PWID in several MENA countries, but do not preclude the possibility of hidden epidemics among PWID in additional MENA countries. Overall, these findings suggest that the HIV epidemic among PWID in MENA is at a relatively early stage. This window of opportunity to control the emerging epidemics should not be missed, warn the researchers. HIV surveillance among PWID in MENA must be expanded to detect and monitor emerging and growing HIV epidemics, they suggest, and to inform effective HIV policy and programming. Improvements in HIV prevention and treatment among PWID in MENA are essential, they conclude, to confront the growing HIV problem in this population and, to prevent the onward transmission of HIV from PWID to other population groups.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001663.
A 2010 report produced by the World Bank, UNAIDS, and WHO provides information on the status of the HIV epidemic in the Middle East and North Africa; the UNAIDS Middle East and North Africa Regional Report on AIDS 2011 provides further information
The 2013 UNAIDS World AIDS Day Report provides up-to-date information about the AIDS epidemic and efforts to halt it
The Middle East and North Africa Harm Reduction Association (MENAHRA) provides information about harm reduction efforts, services, and programs in the Middle East and North Africa; Harm Reduction International provides information about harm reduction concepts, strategies, programs, and publications globally
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
NAM/aidsmap provides basic information about HIV/AIDS, and summaries of recent research findings on HIV care and treatment
Information is available from Avert, an international AIDS charity, on many aspects of HIV/AIDS, including information on people who inject drugs and HIV/AIDS and on harm reduction and HIV prevention (in English and Spanish)
The US National Institute on Drug Abuse also provides information about drug abuse and HIV/AIDS (in English and Spanish)
Personal stories about living with HIV/AIDS are available through Avert, Nam/aidsmap, and Healthtalkonline
doi:10.1371/journal.pmed.1001663
PMCID: PMC4061009  PMID: 24937136
23.  Impact of Antiretroviral Therapy on Incidence of Pregnancy among HIV-Infected Women in Sub-Saharan Africa: A Cohort Study 
PLoS Medicine  2010;7(2):e1000229.
A multicountry cohort study in sub-Saharan Africa by Landon Myer and colleagues reveals higher pregnancy rates in HIV-infected women on antiretroviral therapy (ART).
Background
With the rapid expansion of antiretroviral therapy (ART) services in sub-Saharan Africa there is growing recognition of the importance of fertility and childbearing among HIV-infected women. However there are few data on whether ART initiation influences pregnancy rates.
Methods and Findings
We analyzed data from the Mother-to-Child Transmission-Plus (MTCT-Plus) Initiative, a multicountry HIV care and treatment program for women, children, and families. From 11 programs in seven African countries, women were enrolled into care regardless of HIV disease stage and followed at regular intervals; ART was initiated according to national guidelines on the basis of immunological and/or clinical criteria. Standardized forms were used to collect sociodemographic and clinical data, including incident pregnancies. Overall 589 incident pregnancies were observed among the 4,531 women included in this analysis (pregnancy incidence, 7.8/100 person-years [PY]). The rate of new pregnancies was significantly higher among women receiving ART (9.0/100 PY) compared to women not on ART (6.5/100 PY) (adjusted hazard ratio, 1.74; 95% confidence interval, 1.19–2.54). Other factors independently associated with increased risk of incident pregnancy included younger age, lower educational attainment, being married or cohabiting, having a male partner enrolled into the program, failure to use nonbarrier contraception, and higher CD4 cell counts.
Conclusions
ART use is associated with significantly higher pregnancy rates among HIV-infected women in sub-Saharan Africa. While the possible behavioral or biomedical mechanisms that may underlie this association require further investigation, these data highlight the importance of pregnancy planning and management as a critical but neglected component of HIV care and treatment services.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Human immunodeficiency virus (HIV) causes Acquired Immunodeficiency Syndrome (AIDS), which is a major global cause of disease and death. More than 33 million people around the world are infected with HIV, with nearly 5,500 dying daily from HIV and AIDS-related complications. HIV/AIDS is especially problematic in sub-Saharan Africa, where it is the leading cause of death. There is no cure for HIV/AIDS, but medicines known as “antiretroviral therapy” (ART) can prolong life and reduce complications in patients infected with HIV. 97% of patients with HIV/AIDS live in low- and middle-income countries. According to the World Health Organization, nearly 10 million of these patients need ART. As patients' access to treatment is often hindered by the high cost and low availability of ART, global health efforts have focused on promoting ART use in resource-limited nations. Such efforts also increase awareness of how HIV is spread (contact with blood or semen, in sexual intercourse, sharing needles, or from mother to child during childbirth). ART reduces, but does not remove, the chance of a mother's passing HIV to her child during birth.
Why Was This Study Done?
By the end of 2007, 3 million HIV-infected patients in poor countries were receiving ART. Many of those treated with ART are young women of child-bearing age. Childbirth is an important means of spreading HIV in sub-Saharan Africa, where 60% of all HIV patients are women. This study questions whether the improved health and life expectancy that results from treatment with ART affects pregnancy rates of HIV-infected patients. The study explores this question in seven African countries, by examining the rates of pregnancy in HIV-infected women before and after they started ART.
What Did the Researchers Do and Find?
The authors looked at the records of 4,531 HIV-infected women enrolled in the Mother-to-Child-Transmission-Plus (MTCT-Plus) Initiative in seven African countries. MTCT -Plus, begun in 2002, is a family-centered treatment program that offers regular checkups, blood tests, counseling, and ART treatment (if appropriate) to women and their families. At each checkup, women's CD4+ cell counts and World Health Organization guidelines were used to determine their eligibility for starting ART. Over a 4-year period, nearly a third of the women starting ART experienced a pregnancy: 244 pregnancies occurred in the “pre-ART” group (women not receiving ART) compared to 345 pregnancies in the “on-ART” group (women receiving ART). The chance of pregnancy increased over time in the on-ART group to almost 80% greater than the pre-ART group, while remaining relatively low and constant in the pre-ART group. The authors noted that, as expected, other factors also increased the chances of pregnancy, including younger age, lower educational status, and use of nonbarrier contraception such as injectable hormones.
What Do These Findings Mean?
This study suggests that starting ART is associated with higher pregnancy rates in sub-Saharan Africa, nearly doubling the chances of a woman becoming pregnant. The reasons for this link are unclear. One possible explanation is behavioral: women receiving ART may feel more motivated to have children as their health and quality of life improve. However, the study did not examine how pregnancy desires and sexual activity of women changed while on ART, and cannot discern why ART is linked to increased pregnancy. By using pregnancy data gathered from patient questionnaires rather than laboratory tests, the study is limited by the possibility of inaccurate patient reporting. Understanding how pregnancy rates vary in HIV-infected women receiving ART helps support the formation of responsive, effective HIV programs. Female HIV patients of child-bearing age, who form the majority of patients receiving ART in sub-Saharan Africa, would benefit from programs that combine starting HIV treatment with ART with education and contraception counseling and pregnancy-related care.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000229.
Information is available from the US National Institute of Allergy and Infectious Diseases on HIV infection and AIDS
HIV InSite has comprehensive information on all aspects of HIV/AIDS, including a list of articles and other sources of information about the primary care of adolescents with HIV
A UNAIDS 2008 report is available on the global AIDS epidemic
The International Planned Parenthood Foundation provides information on sexual and reproductive health and HIV
The International Center for AIDS Care and Treatment Programs at the Columbia University Mailman School of Public health provides information to assist HIV care and treatment programs in resource-limited settings
doi:10.1371/journal.pmed.1000229
PMCID: PMC2817715  PMID: 20161723
24.  Increasing Clinical Virulence in Two Decades of the Italian HIV Epidemic 
PLoS Pathogens  2009;5(5):e1000454.
The recent origin and great evolutionary potential of HIV imply that the virulence of the virus might still be changing, which could greatly affect the future of the pandemic. However, previous studies of time trends of HIV virulence have yielded conflicting results. Here we used an established methodology to assess time trends in the severity (virulence) of untreated HIV infections in a large Italian cohort. We characterized clinical virulence by the decline slope of the CD4 count (n = 1423 patients) and the viral setpoint (n = 785 patients) in untreated patients with sufficient data points. We used linear regression models to detect correlations between the date of diagnosis (ranging 1984–2006) and the virulence markers, controlling for gender, exposure category, age, and CD4 count at entry. The decline slope of the CD4 count and the viral setpoint displayed highly significant correlation with the date of diagnosis pointing in the direction of increasing virulence. A detailed analysis of riskgroups revealed that the epidemics of intravenous drug users started with an apparently less virulent virus, but experienced the strongest trend towards steeper CD4 decline among the major exposure categories. While our study did not allow us to exclude the effect of potential time trends in host factors, our findings are consistent with the hypothesis of increasing HIV virulence. Importantly, the use of an established methodology allowed for a comparison with earlier results, which confirmed that genuine differences exist in the time trends of HIV virulence between different epidemics. We thus conclude that there is not a single global trend of HIV virulence, and results obtained in one epidemic cannot be extrapolated to others. Comparison of discordant patterns between riskgroups and epidemics hints at a converging trend, which might indicate that an optimal level of virulence might exist for the virus.
Author Summary
The AIDS epidemic claims more lives per year than any other infectious disease, even though its cause, the Human Immunodeficiency Virus (HIV), is the youngest of all major human pathogens. The recent origin and great evolutionary potential of the virus raise the possibility that the virus might still be adapting to humans. Of primary interest is whether the virulence of the virus, i.e. its ability to cause disease, has been changing over time. Unfortunately, previous results have yielded conflicting results. We investigated time trends of virulence in the Italian HIV epidemic and found increasing virulence. The use of an established methodology allowed, for the first time, direct comparison with results obtained in other epidemics. The comparisons revealed that genuine differences exist in the trends of HIV virulence between different epidemics. Thus, there is no single time trend of HIV virulence worldwide. Our results are consistent with the hypothesis of increasing HIV virulence; however, clinical virulence combines viral and host factors, and the effect of host factors could not be excluded in our analysis.
doi:10.1371/journal.ppat.1000454
PMCID: PMC2682199  PMID: 19478880
25.  Estimating Incidence from Prevalence in Generalised HIV Epidemics: Methods and Validation 
PLoS Medicine  2008;5(4):e80.
Background
HIV surveillance of generalised epidemics in Africa primarily relies on prevalence at antenatal clinics, but estimates of incidence in the general population would be more useful. Repeated cross-sectional measures of HIV prevalence are now becoming available for general populations in many countries, and we aim to develop and validate methods that use these data to estimate HIV incidence.
Methods and Findings
Two methods were developed that decompose observed changes in prevalence between two serosurveys into the contributions of new infections and mortality. Method 1 uses cohort mortality rates, and method 2 uses information on survival after infection. The performance of these two methods was assessed using simulated data from a mathematical model and actual data from three community-based cohort studies in Africa. Comparison with simulated data indicated that these methods can accurately estimates incidence rates and changes in incidence in a variety of epidemic conditions. Method 1 is simple to implement but relies on locally appropriate mortality data, whilst method 2 can make use of the same survival distribution in a wide range of scenarios. The estimates from both methods are within the 95% confidence intervals of almost all actual measurements of HIV incidence in adults and young people, and the patterns of incidence over age are correctly captured.
Conclusions
It is possible to estimate incidence from cross-sectional prevalence data with sufficient accuracy to monitor the HIV epidemic. Although these methods will theoretically work in any context, we have able to test them only in southern and eastern Africa, where HIV epidemics are mature and generalised. The choice of method will depend on the local availability of HIV mortality data.
Timothy Hallett and colleagues develop and test two user-friendly methods to estimate HIV incidence based on changes in cross-sectional prevalence, using either mortality rates or survival after infection.
Editors' Summary
Background.
More than 25 million people have died from AIDS and about 33 million people are currently infected with human immunodeficiency virus (HIV, the virus that causes AIDS). Faced with this threat to human health, governments and international agencies are working together to halt the AIDS epidemic. An important part of this effort is HIV surveillance. The spread of HIV needs to be monitored to assess the impact of interventions (for example, the provision of antiretroviral drugs) and to plan for current and future health care needs. HIV surveillance in countries where the epidemic has spread beyond specific groups into the whole population (a generalized epidemic) has mainly relied on determining the prevalence of HIV infection (the fraction of the population that is infected) among women attending antenatal clinics. Recently, however, household health surveys (for example, the Demographic and Health Surveys) have begun to use blood testing for antibodies to the AIDS virus (serological testing) to provide more accurate estimates of HIV prevalence in the general adult population.
Why Was This Study Done?
Although prevalence estimates provide useful information about the HIV epidemic, another important indicator is incidence—the number of new infections occurring during a specific time period. Incidence measurements provide more information about temporal changes in the epidemic and transmission patterns and allow public-health experts to make better predictions of future health care needs. But, whereas prevalence can be measured with anonymized serological surveys, individuals would have to be identified and followed up in repeat serological surveys to provide a direct measurement of incidence. This is expensive and hard to achieve in many settings. In this study, therefore, the researchers develop and validate two mathematical methods to estimate HIV incidence in generalized HIV epidemics from prevalence data.
What Did the Researchers Do and Find?
Changes in the fraction of the population living with HIV (prevalence) can occur not only because of changes in the rate of new infections (incidence), but also because mortality rates are much higher for infected individuals than others. The researchers' methods disentangle the contributions to HIV prevalence (as measured in serological surveys) made by new infections from those due to deaths from AIDS and other causes. Their first method incorporates information on death rates collected in cohort studies of HIV infection (cohort studies investigate outcomes in groups of people); their second method uses information on survival after HIV infection, also collected in long-running cohort studies. The accuracy of both methods was assessed using computer-simulated data and actual data on HIV prevalence and incidence collected in three community-based cohort studies in Zimbabwe and Uganda (countries with generalized but declining HIV epidemics) and Tanzania (a country with a generalized, stable epidemic). Both methods provided accurate estimates of HIV incidence from the simulated data. Using the data collected in Africa, the mean difference between actual measurements of incidence and the estimate provided by method 1 was 19%; for method 2 it was 14%. In addition, the measured and estimated incidences were in good agreement for all age groups.
What Do These Findings Mean?
These findings suggest HIV incidence rates can be estimated from repeat surveys of prevalence with sufficient accuracy to monitor the HIV epidemic. The accuracy of the estimates across all age groups is particularly important because knowledge of the age-related risk pattern provides the information on transmission patterns that is needed to design effective intervention programs. Because these methods were tested using data only from southern and eastern Africa where the HIV epidemic is mature and generalized, they may not work as well in regions where the epidemic is restricted to subsets of the population. Other factors that might affect their accuracy include the amount of international migration and the uptake of antiretroviral therapies. Nevertheless, with the increased availability of serial measurements of serological prevalence, these new methods for estimating HIV incidence from HIV prevalence could prove extremely useful for monitoring the progress of national HIV epidemics and for guiding HIV control programs. The authors include spreadsheets that can be used to calculate incidence by either method from consecutive survey data.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050080.
The US National Institute of Allergy and Infectious Diseases provides information on HIV infection and AIDS
The US Centers for Disease Control and Prevention provides information on global HIV/AIDS topics (in English and Spanish)
The HIV InSite provides comprehensive and up-to-date information on all aspects of HIV/AIDS from the University of California San Francisco, including country reports on the AIDS epidemic in 195 countries, including Uganda, Zimbabwe, and Tanzania
Avert, an international AIDS charity, provides information on all aspects of HIV/AIDS, including fact sheets on understanding HIV and AIDS statistics, and on HIV and AIDS in Africa
The Demographic and Health Surveys program collects, analyzes, and disseminates information on health and population trends in countries around the world
doi:10.1371/journal.pmed.0050080
PMCID: PMC2288620  PMID: 18590346

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