This analysis combined two population-based data sources to estimate the prevalence of diagnosed HIV infection among sexually active MSM in NYC. Findings suggest an overall high prevalence of diagnosed HIV infection (8.4%), and sensitivity analyses suggest this to be a conservative estimate. The HIV epidemic in NYC disproportionately affects certain segments of the NYC MSM population, particularly non-Hispanic black MSM and MSM in their late 30s–50s. Significant geographic variability also exists in the prevalence of diagnosed HIV infection among sexually active MSM in NYC, with prevalence estimates by borough of residence ranging from less than 2% in Staten Island to approximately 18% in Manhattan. The high prevalence of diagnosed HIV infection among MSM in NYC is likely due to the combination of high HIV incidence over the course of the epidemic and improved survival in the era of HAART.
The population-based estimates of the prevalence of diagnosed HIV infection among sexually active NYC MSM from our analysis are lower than those resulting from studies conducted among high-risk MSM attending STD clinics or other venues known to be frequented by MSM.4–8
Among NYC MSM NHBS participants, the prevalence of HIV infection was 18%7
, and among NYC MSM participating in YMS I and II, HIV prevalences were 12.1 and 17%.5,7
These prevalences are higher than our estimate of the prevalence of diagnosed HIV infection of 8.4%. In the NYC YMS analysis, HIV prevalence was highest among those who were black, Hispanic, or of mixed race/ethnicity and among 20- to 22-year olds.5
Our analysis also revealed a high prevalence of diagnosed HIV infection among sexually active non-Hispanic black MSM, but we identified a lower estimated HIV prevalence (1%) among sexually active MSM in the youngest age group (18–24 years). Methodologic differences between the two studies might account for some of the discrepant findings. The YMS study estimated the prevalence of diagnosed and undiagnosed HIV infection based on serologic testing. HIV surveillance can only account for diagnosed HIV infections that are reported to the HIV/AIDS surveillance registry. We accounted for undiagnosed HIV-infected MSM in our sensitivity analyses to compensate for this limitation. Our overall prevalence estimate increased to 11.2–17.6% when the estimated percent of undiagnosed HIV-infected MSM was included. YMS participants were sampled from public venues frequented by MSM and did not include young MSM who do not frequent such venues. Our population-based estimates are not affected by this selection bias.
In a serosurvey conducted in 1999 among persons attending two public NYC STD clinics, 18% of MSM clinic attendees were determined to be HIV-infected.15
This study was conducted among STD clinic attendees, 60% of whom had an STI diagnosed at the same visit the HIV testing was done, indicating recent unsafe sexual practices and higher risk for HIV infection. Because of the higher risk profile, prevalence estimates based on a serosurvey of MSM attending a public STD clinic are not widely generalizable to the overall NYC MSM population.
The levels of risky behaviors observed in our population-based survey are cause for concern, particularly in light of the high HIV prevalence estimates calculated here. We do not have information on the exact nature of sexual contact or the HIV-status of sexual partners of the MSM in our study population. However, approximately 60% of sexually active MSM reported that a condom was not used during their last sexual encounter, including over one-third of MSM with three or more sex partners in the past year. One in four MSM reported having had one or more recent STIs. This tendency for unsafe sexual practice is reflected in recently reported increases in Neisseria gonorrhoeae16
infections and the emergence of lymphogranuloma venereum18
among NYC MSM. A case-control study conducted among NYC MSM in 2001 reported that 50% of MSM with primary or secondary syphilis were coinfected with HIV and had acquired HIV a median of 7 years before their syphilis diagnosis.19
This finding indicates that risky sexual behaviors are occurring among NYC MSM who are known to be HIV-infected and should have been counseled about reducing risk behaviors.
The number of diagnosed and reported cases of HIV is dependent upon rates of HIV testing. One-third of sexually active MSM reported having been tested for HIV during the past year, and only 46% of MSM with three or more sex partners were tested for HIV during the past year. The prevalence of diagnosed HIV-infection was highest among non-Hispanic black MSM, a racial/ethnic group among whom the prevalence of HIV testing during the previous 12 months was only 38%. Therefore, an even more pronounced racial/ethnic disparity possibly exists in HIV prevalence than our results indicate. Testing rates observed in our study are low, relative to other estimates of HIV testing among MSM. The HIV Testing Surveys are anonymous, cross-sectional interview studies of persons at high-risk for HIV infection.19
Findings from 2002 HITS indicate that 77% of MSM participants had been tested for HIV in the past 12 months.20
A related survey conducted in NYC during 2000–2002 (HITS-NYC) found that 52% of NYC MSM were tested for HIV during the past year.21
Although lower than national estimates, this finding of 52% of MSM reporting having been tested for HIV during the past year is higher than our overall finding of only 34%. As seen with YMS, differences might be the result of the fact that the HITS participants are recruited from venues that are known to be frequented by persons who are at high risk for HIV and are therefore likely to be the focus of HIV prevention and testing programs by community-based organizations.22
However, larger proportions of MSM in certain subgroups, Hispanic (47%), aged 18–24 years (62%), residents of the Bronx (50%), and having more than one sex partner (>46%), reported having been tested for HIV in the past year. These subgroup findings are more consistent with the HITS-NYC result than is our overall finding of 34%.
The findings of this analysis are subject to methodologic limitations. Barriers to obtaining an accurate estimate of the number of HIV-infected MSM from HIV surveillance data include incomplete reporting of HIV transmission risk information to the HIV surveillance system and the presence of undiagnosed cases of HIV-infection. HIV transmission risk information was unknown for almost a quarter of HIV-infected males in our surveillance system as of the end of 2002. An unknown proportion of these males were MSM. In our sensitivity analyses, we calculated HIV prevalence based on varying assumptions regarding what proportion of this population might be MSM. The resulting HIV prevalence estimates ranged from 11–13%. Nationally, an estimated 25% of persons living with HIV infection have not been diagnosed and are unaware of their infection status.14
These persons are therefore not counted by public health surveillance systems and, consequently, are not included in the numerator of our main analysis. Based on the assumption that 25% of HIV-infected persons have not been diagnosed and are unaware of their HIV infection, resulting adjusted HIV prevalence ranged from 11.2–17.6%.
In contrast, other potential biases might serve to artifactually inflate the prevalence estimate. For example, our prevalence estimate includes all HIV-infected MSM identified through the surveillance registry, whether or not they have been sexually active during the past 12 months. However, the target population derived from the CHS for our prevalence estimate is sexually active MSM only, potentially inflating the estimated prevalence. The estimated number of MSM living in NYC is based on males who reported in a household telephone survey that they had sex with one or more males during the previous 12 months. This excludes MSM who have not been sexually active in the past year, such as those who might have ceased sexual activity when they were diagnosed with HIV to reduce transmission risk or because they were too sick to engage in sexual activity.23
Also excluded from the survey estimates were males who have been sexually active with another male during the past year but chose not to disclose that information. Lau et al. investigated differences in responses to sensitive sexual behavior questions between the conventional telephone interview and a computerized data collection method and concluded that respondents were more likely to report risk behaviors when responding to the computerized system.24
Reporting bias due to social desirability might underestimate the number of MSM living in NYC, and thus, overestimate the prevalence of diagnosed HIV infection. If underreporting of MSM varied by race/ethnicity, this would also contribute to observed racial/ethnic disparities in estimated HIV prevalence. Finally, the CHS does not sample the entire NYC population. Persons who live in nonresidential settings, such as prisons and college dormitories, and persons who do not have telephone service or who exclusively use cellular phones were not surveyed, thus, limiting ability to generalize these findings to those populations. Although these restrictions limit generalizability, these populations are not represented in comparable surveys providing national estimates of various health indicators, such as the BRFSS.
Despite high HIV prevalence among sexually active NYC MSM, prevalence of condom use and HIV testing are low. One quarter of sexually active MSM reported having a recent STI, an unknown proportion of whom are coinfected with HIV. The Centers for Disease Control and Prevention emphasizes the incorporation of HIV prevention efforts into the medical care of all HIV-infected persons through provider screening for HIV transmission risk behaviors and STIs, the provision of behavioral risk-reduction interventions, and assistance with partner notification.25
Education and prevention interventions should continue to focus on all MSM in NYC, but particularly those with higher estimated HIV prevalence including those who are non-Hispanic black, aged 35–54 years, and residents of Manhattan. HIV prevention programs should be culturally appropriate and tailored to the needs of the specific target group. Increased awareness of HIV status through frequent testing and safer sex practices among all MSM are essential to reduce transmission of HIV.
Combining data sources provides useful, replicable measures of the prevalence of diagnosed HIV infection among a population at high risk for HIV transmission. Although estimation through use of multiple sources is subject to the limitations described here, the findings are important for ongoing surveillance and targeting resources. Other jurisdictions with large, concentrated HIV epidemics can apply these novel methods to estimate the prevalence of HIV infection among specific at-risk populations such as sexually active persons and injecting drug users and to inform HIV education and prevention programs.