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1.  Long-Term Exposure to Silica Dust and Risk of Total and Cause-Specific Mortality in Chinese Workers: A Cohort Study 
PLoS Medicine  2012;9(4):e1001206.
A retro-prospective cohort study by Weihong Chen and colleagues provides new estimates for the risk of total and cause-specific mortality due to long-term silica dust exposure among Chinese workers.
Background
Human exposure to silica dust is very common in both working and living environments. However, the potential long-term health effects have not been well established across different exposure situations.
Methods and Findings
We studied 74,040 workers who worked at 29 metal mines and pottery factories in China for 1 y or more between January 1, 1960, and December 31, 1974, with follow-up until December 31, 2003 (median follow-up of 33 y). We estimated the cumulative silica dust exposure (CDE) for each worker by linking work history to a job–exposure matrix. We calculated standardized mortality ratios for underlying causes of death based on Chinese national mortality rates. Hazard ratios (HRs) for selected causes of death associated with CDE were estimated using the Cox proportional hazards model. The population attributable risks were estimated based on the prevalence of workers with silica dust exposure and HRs. The number of deaths attributable to silica dust exposure among Chinese workers was then calculated using the population attributable risk and the national mortality rate. We observed 19,516 deaths during 2,306,428 person-years of follow-up. Mortality from all causes was higher among workers exposed to silica dust than among non-exposed workers (993 versus 551 per 100,000 person-years). We observed significant positive exposure–response relationships between CDE (measured in milligrams/cubic meter–years, i.e., the sum of silica dust concentrations multiplied by the years of silica exposure) and mortality from all causes (HR 1.026, 95% confidence interval 1.023–1.029), respiratory diseases (1.069, 1.064–1.074), respiratory tuberculosis (1.065, 1.059–1.071), and cardiovascular disease (1.031, 1.025–1.036). Significantly elevated standardized mortality ratios were observed for all causes (1.06, 95% confidence interval 1.01–1.11), ischemic heart disease (1.65, 1.35–1.99), and pneumoconiosis (11.01, 7.67–14.95) among workers exposed to respirable silica concentrations equal to or lower than 0.1 mg/m3. After adjustment for potential confounders, including smoking, silica dust exposure accounted for 15.2% of all deaths in this study. We estimated that 4.2% of deaths (231,104 cases) among Chinese workers were attributable to silica dust exposure. The limitations of this study included a lack of data on dietary patterns and leisure time physical activity, possible underestimation of silica dust exposure for individuals who worked at the mines/factories before 1950, and a small number of deaths (4.3%) where the cause of death was based on oral reports from relatives.
Conclusions
Long-term silica dust exposure was associated with substantially increased mortality among Chinese workers. The increased risk was observed not only for deaths due to respiratory diseases and lung cancer, but also for deaths due to cardiovascular disease.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Walk along most sandy beaches and you will be walking on millions of grains of crystalline silica, one of the commonest minerals on earth and a major ingredient in glass and in ceramic glazes. Silica is also used in the manufacture of building materials, in foundry castings, and for sandblasting, and respirable (breathable) crystalline silica particles are produced during quarrying and mining. Unfortunately, silica dust is not innocuous. Several serious diseases are associated with exposure to this dust, including silicosis (a chronic lung disease characterized by scarring and destruction of lung tissue), lung cancer, and pulmonary tuberculosis (a serious lung infection). Moreover, exposure to silica dust increases the risk of death (mortality). Worryingly, recent reports indicate that in the US and Europe, about 1.7 and 3.0 million people, respectively, are occupationally exposed to silica dust, figures that are dwarfed by the more than 23 million workers who are exposed in China. Occupational silica exposure, therefore, represents an important global public health concern.
Why Was This Study Done?
Although the lung-related adverse health effects of exposure to silica dust have been extensively studied, silica-related health effects may not be limited to these diseases. For example, could silica dust particles increase the risk of cardiovascular disease (diseases that affect the heart and circulation)? Other environmental particulates, such as the products of internal combustion engines, are associated with an increased risk of cardiovascular disease, but no one knows if the same is true for silica dust particles. Moreover, although it is clear that high levels of exposure to silica dust are dangerous, little is known about the adverse health effects of lower exposure levels. In this cohort study, the researchers examined the effect of long-term exposure to silica dust on the risk of all cause and cause-specific mortality in a large group (cohort) of Chinese workers.
What Did the Researchers Do and Find?
The researchers estimated the cumulative silica dust exposure for 74,040 workers at 29 metal mines and pottery factories from 1960 to 2003 from individual work histories and more than four million measurements of workplace dust concentrations, and collected health and mortality data for all the workers. Death from all causes was higher among workers exposed to silica dust than among non-exposed workers (993 versus 551 deaths per 100,000 person-years), and there was a positive exposure–response relationship between silica dust exposure and death from all causes, respiratory diseases, respiratory tuberculosis, and cardiovascular disease. For example, the hazard ratio for all cause death was 1.026 for every increase in cumulative silica dust exposure of 1 mg/m3-year; a hazard ratio is the incidence of an event in an exposed group divided by its incidence in an unexposed group. Notably, there was significantly increased mortality from all causes, ischemic heart disease, and silicosis among workers exposed to respirable silica concentrations at or below 0.1 mg/m3, the workplace exposure limit for silica dust set by the US Occupational Safety and Health Administration. For example, the standardized mortality ratio (SMR) for silicosis among people exposed to low levels of silica dust was 11.01; an SMR is the ratio of observed deaths in a cohort to expected deaths calculated from recorded deaths in the general population. Finally, the researchers used their data to estimate that, in 2008, 4.2% of deaths among industrial workers in China (231,104 deaths) were attributable to silica dust exposure.
What Do These Findings Mean?
These findings indicate that long-term silica dust exposure is associated with substantially increased mortality among Chinese workers. They confirm that there is an exposure–response relationship between silica dust exposure and a heightened risk of death from respiratory diseases and lung cancer. That is, the risk of death from these diseases increases as exposure to silica dust increases. In addition, they show a significant relationship between silica dust exposure and death from cardiovascular diseases. Importantly, these findings suggest that even levels of silica dust that are considered safe increase the risk of death. The accuracy of these findings may be affected by the accuracy of the silica dust exposure estimates and/or by confounding (other factors shared by the people exposed to silica such as diet may have affected their risk of death). Nevertheless, these findings highlight the need to tighten regulations on workplace dust control in China and elsewhere.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001206.
The American Lung Association provides information on silicosis
The US Centers for Disease Control and Prevention provides information on silica in the workplace, including links to relevant US National Institute for Occupational Health and Safety publications, and information on silicosis and other pneumoconioses
The US Occupational Safety and Health Administration also has detailed information on occupational exposure to crystalline silica
What does silicosis mean to you is a video provided by the US Mine Safety and Health Administration that includes personal experiences of silicosis; Dont let silica dust you is a video produced by the Association of Occupational and Environmental Clinics that identifies ways to reduce silica dust exposure in the workplace
The MedlinePlus encyclopedia has a page on silicosis (in English and Spanish)
The International Labour Organization provides information on health surveillance for those exposed to respirable crystalline silica
The World Health Organization has published a report about the health effects of crystalline silica and quartz
doi:10.1371/journal.pmed.1001206
PMCID: PMC3328438  PMID: 22529751
2.  Knowledge of occupational exposure to HIV: a cross sectional study of healthcare workers in Tumbi and Dodoma hospitals, Tanzania 
Background
Insufficient knowledge on blood-borne pathogens has been identified as a factor that influences occupational exposure to needle stick and sharps injuries. The objective of this study was to assess healthcare workers’ knowledge on occupational exposure to HIV.
Methods
A cross sectional survey was conducted at Tumbi designated regional hospital and Dodoma regional hospital, Tanzania in February 2012. A self-administered questionnaire was used to capture information on knowledge of occupational exposure to HIV infection.
Results
A total of 401 healthcare workers responded to a self-administered questionnaire. High proportion of healthcare workers (96.3%) understood that they are at risk of occupational exposure to HIV. The majority of healthcare workers trained on post exposure prophylaxis procedure and use of personal protective equipment were clinicians (87.1% and 71.4% respectively) and nurses (81.8% and 74.6% respectively). Over a quarter of the healthcare workers were not aware of whom to contact in the event of occupational exposure. One third of healthcare workers did not have comprehensive knowledge on causes of occupational HIV transmission and did not know when post exposure prophylaxis is indicated. Healthcare workers not trained on the use of person protective equipment were less likely to have comprehensive knowledge on occupational exposure to HIV (OR = 0.5; 95% CI 0.3 – 0.9). Knowledge on causes of occupational exposure varied with the cadre of healthcare workers. Nurses were more likely to have comprehensive knowledge on occupational exposure to HIV than non-clinical staff (OR = 2.6; 95% CI 1.5 – 4.5).
Conclusion
A substantial proportion of studied healthcare workers had little knowledge on occupational exposure to HIV and was not aware of a contact person in the event of occupational exposure to HIV. Training on post exposure prophylaxis and infection prevention and control including the use of person protective equipment provided to nurses and clinicians should be extended to other clinical and non-clinical hospital staff.
doi:10.1186/s12913-015-0700-z
PMCID: PMC4307904  PMID: 25609261
Knowledge; Occupational exposure; HIV transmission; Healthcare workers
3.  Mortality in Iraq Associated with the 2003–2011 War and Occupation: Findings from a National Cluster Sample Survey by the University Collaborative Iraq Mortality Study 
PLoS Medicine  2013;10(10):e1001533.
Based on a survey of 2,000 randomly selected households throughout Iraq, Amy Hagopian and colleagues estimate that close to half a million excess deaths are attributable to the recent Iraq war and occupation.
Please see later in the article for the Editors' Summary
Background
Previous estimates of mortality in Iraq attributable to the 2003 invasion have been heterogeneous and controversial, and none were produced after 2006. The purpose of this research was to estimate direct and indirect deaths attributable to the war in Iraq between 2003 and 2011.
Methods and Findings
We conducted a survey of 2,000 randomly selected households throughout Iraq, using a two-stage cluster sampling method to ensure the sample of households was nationally representative. We asked every household head about births and deaths since 2001, and all household adults about mortality among their siblings. We used secondary data sources to correct for out-migration. From March 1, 2003, to June 30, 2011, the crude death rate in Iraq was 4.55 per 1,000 person-years (95% uncertainty interval 3.74–5.27), more than 0.5 times higher than the death rate during the 26-mo period preceding the war, resulting in approximately 405,000 (95% uncertainty interval 48,000–751,000) excess deaths attributable to the conflict. Among adults, the risk of death rose 0.7 times higher for women and 2.9 times higher for men between the pre-war period (January 1, 2001, to February 28, 2003) and the peak of the war (2005–2006). We estimate that more than 60% of excess deaths were directly attributable to violence, with the rest associated with the collapse of infrastructure and other indirect, but war-related, causes. We used secondary sources to estimate rates of death among emigrants. Those estimates suggest we missed at least 55,000 deaths that would have been reported by households had the households remained behind in Iraq, but which instead had migrated away. Only 24 households refused to participate in the study. An additional five households were not interviewed because of hostile or threatening behavior, for a 98.55% response rate. The reliance on outdated census data and the long recall period required of participants are limitations of our study.
Conclusions
Beyond expected rates, most mortality increases in Iraq can be attributed to direct violence, but about a third are attributable to indirect causes (such as from failures of health, sanitation, transportation, communication, and other systems). Approximately a half million deaths in Iraq could be attributable to the war.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
War is a major public health problem. Its health effects include violent deaths among soldiers and civilians as well as indirect increases in mortality and morbidity caused by conflict. Unlike those of other causes of death and disability, however, the consequences of war on population health are rarely studied scientifically. In conflict situations, deaths and diseases are not reliably measured and recorded, and estimating the proportion caused, directly or indirectly, by a war or conflict is challenging. Population-based mortality survey methods—asking representative survivors about deaths they know about—were developed by public health researchers to estimate death rates. By comparing death rate estimates for periods before and during a conflict, researchers can derive the number of excess deaths that are attributable to the conflict.
Why Was This Study Done?
A number of earlier studies have estimated the death toll in Iraq since the beginning of the war in March 2003. The previous studies covered different periods from 2003 to 2006 and derived different rates of overall deaths and excess deaths attributable to the war and conflict. All of them have been controversial, and their methodologies have been criticized. For this study, based on a population-based mortality survey, the researchers modified and improved their methodology in response to critiques of earlier surveys. The study covers the period from the beginning of the war in March 2003 until June 2011, including a period of high violence from 2006 to 2008. It provides population-based estimates for excess deaths in the years after 2006 and covers most of the period of the war and subsequent occupation.
What Did the Researchers Do and Find?
Interviewers trained by the researchers conducted the survey between May 2011 and July 2011 and collected data from 2,000 randomly selected households in 100 geographical clusters, distributed across Iraq's 18 governorates. The interviewers asked the head of each household about deaths among household members from 2001 to the time of the interview, including a pre-war period from January 2001 to March 2003 and the period of the war and occupation. They also asked all adults in the household about deaths among their siblings during the same period. From the first set of data, the researchers calculated the crude death rates (i.e., the number of deaths during a year per 1,000 individuals) before and during the war. They found the wartime crude death rate in Iraq to be 4.55 per 1,000, more than 50% higher than the death rate of 2.89 during the two-year period preceding the war. By multiplying those rates by the annual Iraq population, the authors estimate the total excess Iraqi deaths attributable to the war through mid-2011 to be about 405,000. The researchers also estimated that an additional 56,000 deaths were not counted due to migration. Including this number, their final estimate is that approximately half a million people died in Iraq as a result of the war and subsequent occupation from March 2003 to June 2011.
The risk of death at the peak of the conflict in 2006 almost tripled for men and rose by 70% for women. Respondents attributed 20% of household deaths to war-related violence. Violent deaths were attributed primarily to coalition forces (35%) and militia (32%). The majority (63%) of violent deaths were from gunshots. Twelve percent were attributed to car bombs. Based on the responses from adults in the surveyed households who reported on the alive-or-dead status of their siblings, the researchers estimated the total number of deaths among adults aged 15–60 years, from March 2003 to June 2011, to be approximately 376,000; 184,000 of these deaths were attributed to the conflict, and of those, the authors estimate that 132,000 were caused directly by war-related violence.
What Do These Findings Mean?
These findings provide the most up-to-date estimates of the death toll of the Iraq war and subsequent conflict. However, given the difficult circumstances, the estimates are associated with substantial uncertainties. The researchers extrapolated from a small representative sample of households to estimate Iraq's national death toll. In addition, respondents were asked to recall events that occurred up to ten years prior, which can lead to inaccuracies. The researchers also had to rely on outdated census data (the last complete population census in Iraq dates back to 1987) for their overall population figures. Thus, to accompany their estimate of 460,000 excess deaths from March 2003 to mid-2011, the authors used statistical methods to determine the likely range of the true estimate. Based on the statistical methods, the researchers are 95% confident that the true number of excess deaths lies between 48,000 and 751,000—a large range. More than two years past the end of the period covered in this study, the conflict in Iraq is far from over and continues to cost lives at alarming rates. As discussed in an accompanying Perspective by Salman Rawaf, violence and lawlessness continue to the present day. In addition, post-war Iraq has limited capacity to re-establish and maintain its battered public health and safety infrastructure.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001533
This study is further discussed in a PLOS Medicine Perspective by Salman Rawaf.
The Geneva Declaration on Armed Violence and Development website provides information on the global burden of armed violence.
The International Committee of the Red Cross provides information about war and international humanitarian law (in several languages).
Medact, a global health charity, has information on health and conflict.
Columbia University has a program on forced migration and health.
Johns Hopkins University runs the Center for Refugee and Disaster Response.
University of Washington's Health Alliance International website also has information about war and conflict.
doi:10.1371/journal.pmed.1001533
PMCID: PMC3797136  PMID: 24143140
4.  Sustained Low Influenza Vaccination Rates in US Healthcare Workers 
Preventive medicine  2010;50(4):210-212.
INTRODUCTION
A substantial morbidity and mortality burden attributable to the influenza virus is observed annually in the United States. Healthcare workers are an occupational group at increased risk of exposure, demonstrated to transmit influenza to their patient populations, and vital to the care of these patient populations. The prevention of the spread of the flu is a significant public health concern. In the present study, we examined influenza vaccination rates and their 5-year trends within the major occupational healthcare worker groups and compared them to non-Healthcare Workers.
METHODS
Using data from the nationally representative 2004–2008 National Health Interview Survey (NHIS), US healthcare workers (n=6,394) were analyzed.
RESULTS
Seasonal influenza vaccination coverage estimates remain substantially low among all healthcare workers, highest among the health diagnosing and treating practitioners (52.3%), and lowest among other healthcare support occupations (32.0%). Among all other occupational groups, pooled influenza vaccination rates were highest for white collar workers (24.7%), and lowest for farm workers (11.7%). There were no significant upward or downward trends in influenza vaccination rates for any healthcare or other occupational worker group during the five-year survey period.
CONCLUSION
Improving these low vaccination rates among healthcare workers warrants a comprehensive national approach to influenza prevention that includes education and strong encouragement of routine annual vaccination among healthcare workers. Policy enhancements such as free provision of seasonal influenza vaccine, coverage for treatment and workers compensation for vaccine-related complications are needed.
doi:10.1016/j.ypmed.2010.01.001
PMCID: PMC2839028  PMID: 20079761
Flu; Vaccination; healthcare workers; occupation; epidemiology
5.  Healthcare provider smoking cessation advice among US worker groups 
Tobacco Control  2007;16(5):325-328.
Objective
Among workers in dusty occupations, tobacco use is particularly detrimental to health because of the potential synergistic effects of occupational exposures (for example, asbestos) in causing disease. This study explored the prevalence of smoking and the reported smoking cessation discussion with a primary healthcare provider (HCP) among a representative sample of currently employed US worker groups.
Methods
Pooled data from the 1997–2003 National Health Interview Survey (NHIS) were used to estimate occupation specific smoking rates (n = 135 412). The 2000 NHIS Cancer Control Module was used to determine (among employed smokers with HCP visits) the prevalence of being advised to quit smoking by occupation (n = 3454).
Results
The average annual prevalence of current smoking was 25% in all workers. In 2000, 84% of smokers reported visiting an HCP during the past 12 months; 53% reported being advised by their physician to quit smoking (range 42%–66% among 30 occupations). However, an estimated 10.5 million smokers were not advised to quit smoking by their HCP. Workers with potentially increased occupational exposure to dusty work environments (including asbestos, silica, particulates, etc), at high risk for occupational lung disease and with high smoking prevalence, had relatively low reported discussions with an HCP about smoking cessation, including farm workers (30% overall smoking prevalence; 42% told to quit), construction and extractive trades (39%; 46%), and machine operators/tenderers (34%; 44%).
Conclusion
The relatively low reported prevalence of HCP initiated smoking cessation discussion, particularly among currently employed workers with potentially synergistic occupational exposures and high current smoking prevalence, needs to be addressed through educational campaigns targeting physicians and other HCPs.
doi:10.1136/tc.2006.019117
PMCID: PMC2598555  PMID: 17897991
occupational health; National Health Interview Survey; tobacco use
6.  Tuberculosis in Healthcare Workers and Infection Control Measures at Primary Healthcare Facilities in South Africa 
PLoS ONE  2013;8(10):e76272.
Background
Challenges exist regarding TB infection control and TB in hospital-based healthcare workers in South Africa. However, few studies report on TB in non-hospital based healthcare workers such as primary or community healthcare workers. Our objectives were to investigate the implementation of TB infection control measures at primary healthcare facilities, the smear positive TB incidence rate amongst primary healthcare workers and the association between TB infection control measures and all types of TB in healthcare workers.
Methods
One hundred and thirty three primary healthcare facilities were visited in five provinces of South Africa in 2009. At each facility, a TB infection control audit and facility questionnaire were completed. The number of healthcare workers who had had TB during the past three years was obtained.
Results
The standardised incidence ratio of smear positive TB in primary healthcare workers indicated an incidence rate of more than double that of the general population. In a univariable logistic regression, the infection control audit score was significantly associated with reported cases of TB in healthcare workers (OR=1.04, 95%CI 1.01-1.08, p=0.02) as was the number of staff (OR=3.78, 95%CI 1.77-8.08). In the multivariable analysis, the number of staff remained significantly associated with TB in healthcare workers (OR=3.33, 95%CI 1.37-8.08).
Conclusion
The high rate of TB in healthcare workers suggests a substantial nosocomial transmission risk, but the infection control audit tool which was used did not perform adequately as a measure of this risk. Infection control measures should be monitored by validated tools developed and tested locally. Different strategies, such as routine surveillance systems, could be used to evaluate the burden of TB in healthcare workers in order to calculate TB incidence, monitor trends and implement interventions to decrease occupational TB.
doi:10.1371/journal.pone.0076272
PMCID: PMC3788748  PMID: 24098461
7.  A study of hepatitis C prevalence in healthcare workers in the West of Scotland 
Gut  2001;48(1):116-120.
BACKGROUND AND AIMS—Whether healthcare workers have an increased prevalence of hepatitis C virus infection as a result of exposure to patient's blood and body fluids is controversial. This study assesses the prevalence of hepatitis C virus infection in healthcare workers, and its relation to the performance of exposure prone procedures and duration of occupational exposure, allowing an estimate to be made of the incidence of occupationally acquired hepatitis C infection among medical staff.
METHODS—In this anonymous retrospective cohort study, we estimated the prevalence of hepatitis C infection in 10 654 healthcare workers. ELISA-3 testing was performed on pools of five sera collected during immunisation against hepatitis B. Healthcare workers were arranged into five occupational groups, according to the degree of patient exposure, and three age bands (<30 years, 30-39 years, >40 years).
RESULTS—Prevalence of antibodies to hepatitis C was 0.28% (30/10 654), comparable in all occupational groups (p=0.34) and unrelated to duration of potential exposure. Assuming that all detected infections had been occupationally acquired, the maximum estimated risk of hepatitis C infection in exposure prone medical staff was low: 1.4% for surgeons and 1.0% for physicians over a 35 year professional career.
CONCLUSIONS—Hepatitis C infection is infrequent in healthcare workers in Glasgow. Those conducting exposure prone procedures do not seem to be at higher risk than other healthcare staff.


Keywords: hepatitis C virus; epidemiology; exposure prone procedures; healthcare worker
doi:10.1136/gut.48.1.116
PMCID: PMC1728181  PMID: 11115832
8.  Protecting patients, protecting healthcare workers: a review of the role of influenza vaccination 
International Nursing Review  2011;59(2):161-167.
MUSIC T. (2012) A review of the role the role of influenza vaccination in protecting patients, protecting healthcare workers the role of influenza vaccination. International Nursing Review59, 161–167
Aim:
Many health authorities recommend routine influenza vaccination for healthcare workers (HCWs), and during the 2009 A (H1N1) pandemic, the World Health Organization (WHO) recommended immunization of all HCWs worldwide. As this remains an important area of policy debate, this paper examines the case for vaccination, the role of local guidelines, barriers to immunization and initiatives to increase uptake.
Background:
Seasonal influenza is a major threat to public health, causing up to 1 million deaths annually. Extensive evidence supports the vaccination of priority groups, including HCWs. Immunization protects HCWs themselves, and their vulnerable patients from nosocomial influenza infections. In addition, influenza can disrupt health services and impact healthcare organizations financially. Immunization can reduce staff absences, offer cost savings and provide economic benefits.
Methods:
This paper reviews official immunization recommendations and HCW vaccination studies, including a recent International Federation of Pharmaceutical Manufacturers and Associations (IFPMA) survey of 26 countries from each region of the world.
Results:
HCW immunization is widely recommended and supported by the WHO. In the IFPMA study, 88% of countries recommended HCW vaccination, and 61% supported this financially (with no correlation to country development status). Overall, coverage can be improved, and research shows that uptake may be impacted by lack of conveniently available vaccines and misconceptions regarding vaccine safety/efficacy and influenza risk.
Conclusions:
Many countries recommend HCW vaccination against influenza. In recent years, there has been an increased uptake rate among HCWs in some countries, but not in others. Several initiatives can increase coverage, including education, easy access to free vaccines and the use of formal declination forms. The case for HCW vaccination is clear, and in an effort to further accelerate uptake as a patient safety measure, an increasing number of healthcare organizations, particularly in the USA, are implementing mandatory immunization policies, similar to other obligatory hygiene measures. However, it would be desirable if similar high vaccination uptake rates could be achieved through voluntary procedures.
doi:10.1111/j.1466-7657.2011.00961.x
PMCID: PMC3418836  PMID: 22591085
Coverage; Education; Guideline; Influenza; Policy; Recommendation; Reimbursement; Seasonal; Vaccine
9.  Tuberculosis among Health-Care Workers in Low- and Middle-Income Countries: A Systematic Review 
PLoS Medicine  2006;3(12):e494.
Background
The risk of transmission of Mycobacterium tuberculosis from patients to health-care workers (HCWs) is a neglected problem in many low- and middle-income countries (LMICs). Most health-care facilities in these countries lack resources to prevent nosocomial transmission of tuberculosis (TB).
Methods and Findings
We conducted a systematic review to summarize the evidence on the incidence and prevalence of latent TB infection (LTBI) and disease among HCWs in LMICs, and to evaluate the impact of various preventive strategies that have been attempted. To identify relevant studies, we searched electronic databases and journals, and contacted experts in the field. We identified 42 articles, consisting of 51 studies, and extracted data on incidence, prevalence, and risk factors for LTBI and disease among HCWs. The prevalence of LTBI among HCWs was, on average, 54% (range 33% to 79%). Estimates of the annual risk of LTBI ranged from 0.5% to 14.3%, and the annual incidence of TB disease in HCWs ranged from 69 to 5,780 per 100,000. The attributable risk for TB disease in HCWs, compared to the risk in the general population, ranged from 25 to 5,361 per 100,000 per year. A higher risk of acquiring TB disease was associated with certain work locations (inpatient TB facility, laboratory, internal medicine, and emergency facilities) and occupational categories (radiology technicians, patient attendants, nurses, ward attendants, paramedics, and clinical officers).
Conclusions
In summary, our review demonstrates that TB is a significant occupational problem among HCWs in LMICs. Available evidence reinforces the need to design and implement simple, effective, and affordable TB infection-control programs in health-care facilities in these countries.
A systematic review demonstrates that tuberculosis is an important occupational problem among health care workers in low and middle-income countries.
Editors' Summary
Background.
One third of the world's population is infected with Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB). In many people, the bug causes no health problems—it remains latent. But about 10% of infected people develop active, potentially fatal TB, often in their lungs. People with active pulmonary TB readily spread the infection to other people, including health-care workers (HCWs), in small airborne droplets produced when they cough or sneeze. In high-income countries such as the US, guidelines are in place to minimize the transmission of TB in health-care facilities. Administrative controls (for example, standard treatment plans for people with suspected or confirmed TB) aim to reduce the exposure of HCWs to people with TB. Environmental controls (for example, the use of special isolation rooms) aim to prevent the spread and to reduce the concentration of infectious droplets in the air. Finally, respiratory-protection controls (for example, personal respirators for nursing staff) aim to reduce the risk of infection when exposure to M. tuberculosis is unavoidably high. Together, these three layers of control have reduced the incidence of TB in HCWs (the number who catch TB annually) in high-income countries.
Why Was This Study Done?
But what about low- and middle-income countries (LMICs) where more than 90% of the world's cases of TB occur? Here, there is little money available to implement even low-cost strategies to reduce TB transmission in health-care facilities—so how important an occupational disease is TB in HCWs in these countries? In this study, the researchers have systematically reviewed published papers to find out the incidence and prevalence (how many people in a population have a specific disease) of active TB and latent TB infections (LTBIs) in HCWs in LMICs. They have also investigated whether any of the preventative strategies used in high-income countries have been shown to reduce the TB burden in HCWs in poorer countries.
What Did the Researchers Do and Find?
To identify studies on TB transmission to HCWs in LMICs, the researchers searched electronic databases and journals, and also contacted experts on TB transmission. They then extracted and analyzed the relevant data on TB incidence, prevalence, risk factors, and control measures. Averaged-out over the 51 identified studies, 54% of HCWs had LTBI. In most of the studies, increasing age and duration of employment in health-care facilities, indicating a longer cumulative exposure to infection, was associated with a higher prevalence of LTBI. The same trend was seen in a subgroup of medical and nursing students. After accounting for the incidence of TB in the relevant general population, the excess incidence of TB in the different studies that was attributable to being a HCW ranged from 25 to 5,361 cases per 100, 000 people per year. In addition, a higher risk of acquiring TB was associated with working in specific locations (for example, inpatient TB facilities or diagnostic laboratories) and with specific occupations, including nurses and radiology attendants; most of the health-care facilities examined in the published studies had no specific TB infection-control programs in place.
What Do These Findings Mean?
As with all systematic reviews, the accuracy of these findings may be limited by some aspects of the original studies, such as how the incidence of LTBI was measured. In addition, the possibility that the researchers missed some relevant published studies, or that only studies where there was a high incidence of TB in HCWs were published, may also affect the findings of this study. Nevertheless, they suggest that TB is an important occupational disease in HCWs in LMICs and that the HCWs most at risk of TB are those exposed to the most patients with TB. Reduction of that risk should be a high priority because occupational TB leads to the loss of essential, skilled HCWs. Unfortunately, there are few data available to indicate how this should be done. Thus, the researchers conclude, well-designed field studies are urgently needed to evaluate whether the TB-control measures that have reduced TB transmission to HCWs in high-income countries will work and be affordable in LMICs.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0030494.
• US National Institute of Allergy and Infectious Diseases patient fact sheet on tuberculosis
• US Centers for Disease Control and Prevention information for patients and professionals on tuberculosis
• MedlinePlus encyclopedia entry on tuberculosis
• NHS Direct Online, from the UK National Health Service, patient information on tuberculosis
• US National Institute for Occupational Health and Safety, information about tuberculosis for health-care workers
• American Lung Association information on tuberculosis and health-care workers
doi:10.1371/journal.pmed.0030494
PMCID: PMC1716189  PMID: 17194191
10.  Quantifying the Number of Pregnancies at Risk of Malaria in 2007: A Demographic Study 
PLoS Medicine  2010;7(1):e1000221.
By combining data from the Malaria Atlas Project with country-specific data, Feiko ter Kuile and colleagues provide the first contemporary global estimates of the annual number of pregnancies at risk of malaria.
Background
Comprehensive and contemporary estimates of the number of pregnancies at risk of malaria are not currently available, particularly for endemic areas outside of Africa. We derived global estimates of the number of women who became pregnant in 2007 in areas with Plasmodium falciparum and P. vivax transmission.
Methods and Findings
A recently published map of the global limits of P. falciparum transmission and an updated map of the limits of P. vivax transmission were combined with gridded population data and growth rates to estimate total populations at risk of malaria in 2007. Country-specific demographic data from the United Nations on age, sex, and total fertility rates were used to estimate the number of women of child-bearing age and the annual rate of live births. Subregional estimates of the number of induced abortions and country-specific stillbirths rates were obtained from recently published reviews. The number of miscarriages was estimated from the number of live births and corrected for induced abortion rates. The number of clinically recognised pregnancies at risk was then calculated as the sum of the number of live births, induced abortions, spontaneous miscarriages, and stillbirths among the population at risk in 2007. In 2007, 125.2 million pregnancies occurred in areas with P. falciparum and/or P. vivax transmission resulting in 82.6 million live births. This included 77.4, 30.3, 13.1, and 4.3 million pregnancies in the countries falling under the World Health Organization (WHO) regional offices for South-East-Asia (SEARO) and the Western-Pacific (WPRO) combined, Africa (AFRO), Europe and the Eastern Mediterranean (EURO/EMRO), and the Americas (AMRO), respectively. Of 85.3 million pregnancies in areas with P. falciparum transmission, 54.7 million occurred in areas with stable transmission and 30.6 million in areas with unstable transmission (clinical incidence <1 per 10,000 population/year); 92.9 million occurred in areas with P. vivax transmission, 53.0 million of which occurred in areas in which P. falciparum and P. vivax co-exist and 39.9 million in temperate regions with P. vivax transmission only.
Conclusions
In 2007, 54.7 million pregnancies occurred in areas with stable P. falciparum malaria and a further 70.5 million in areas with exceptionally low malaria transmission or with P. vivax only. These represent the first contemporary estimates of the global distribution of the number of pregnancies at risk of P. falciparum and P. vivax malaria and provide a first step towards a more informed estimate of the geographical distribution of infection rates and the corresponding disease burden of malaria in pregnancy.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Malaria, a mosquito-borne parasitic disease, is a major global public-health problem. About half of the world's population is at risk of malaria, which kills about one million people every year. Most of these deaths are caused by Plasmodium falciparum, which thrives in tropical and subtropical regions. However, the most widely distributed type of malaria is P. vivax malaria, which also occurs in temperate regions. Most malaria deaths are among young children in sub-Saharan Africa, but pregnant women and their unborn babies are also very vulnerable to malaria. About 10,000 women and 200,000 babies die annually because of malaria in pregnancy, which can cause miscarriages, preterm births, and low-birth-weight births. Over the past decade, a three-pronged approach has been developed to prevent and control malaria in pregnancy. This approach consists of intermittent preventative treatment of pregnant women with antimalarial drugs, the use of insecticide-treated bed nets to protect pregnant women from the bites of infected mosquitoes, and management of malarial illness among pregnant women.
Why Was This Study Done?
This strategy has begun to reduce the burden of malaria among pregnant women and their babies but the resources available for its introduction are very limited in many of the developing countries where malaria is endemic (always present). Policy makers in these countries need to know the number of pregnancies at risk of malaria so that they can use their resources wisely. However, although the World Health Organization recently estimated that more than 30 million African women living in malaria endemic areas become pregnant and are at risk for malaria each year, there are no comprehensive and contemporary estimates of the number of pregnancies at risk of malaria for endemic areas outside Africa. In this study, the researchers derive global estimates of the number of women who became pregnant in 2007 in areas with P. falciparum and P. vivax transmission.
What Did the Researchers Do and Find?
The researchers estimated the sizes of populations at risk of malaria in 2007 by combining maps of the global limits of P. vivax and P. falciparum transmission with data on population densities. They used data from various sources to calculate the annual number of pregnancies (the sum of live births, induced abortions, miscarriages, and still births) in each country. Finally, they calculated the annual number of pregnancies at risk of malaria in each country by multiplying the number of pregnancies in the entire country by the fraction of the population living within the spatial limits of malaria transmission in that country. In 2007, they calculate, 125.2 million pregnancies occurred in areas with P. falciparum and/or P. vivax transmission. These pregnancies—60% of all pregnancies globally—resulted in 82.6 million live births. 77.4 million at-risk pregnancies occurred in Southeast Asia and the Western Pacific (India had the most pregnancies at risk of both P. falciparum and P. vivax malaria), 30.3 million in Africa, 13.1 million in Europe and the Eastern Mediterranean, and 4.3 million in the Americas. 54.7 million at-risk pregnancies occurred in regions with stable P. falciparum transmission (more than one case of malaria per 10,000 people per year), whereas 70.5 million occurred in areas with low malaria transmission or P. vivax transmission only.
What Do These Findings Mean?
These findings are the first contemporary estimates of the global distribution of the number of pregnancies at risk of P. falciparum and P. vivax malaria. They do not provide any information on the actual incidence of malaria during pregnancy or the health burden on mothers and unborn babies. They simply represent “any risk” of exposure. So, for example, the researchers calculate that only about 5,000 actual malaria infections may occur annually among the 70.5 million at-risk pregnancies in areas with very low malaria transmission or with P. vivax transmission only. Furthermore, these findings do not allow for the seasonality of malaria—pregnancies that occur outside of the transmission season may be at no or very low risk of malaria. Nevertheless, the estimates reported in this study are an important first step towards a spatial map of the burden of malaria in pregnancy and should help policy makers allocate resources for research into and control of this important public-health problem.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000221.
Information is available from the World Health Organization on malaria and on malaria in pregnancy (in several languages)
The US Centers for Disease Control and Prevention also provides information on malaria and on malaria in pregnancy (in English and Spanish)
Information is available from the Roll Back Malaria Partnership on all aspects of global malaria control, including information on malaria in pregnancy
The Malaria in Pregnancy Consortium is undertaking research into the prevention and treatment of malaria in pregnancy and also provides a comprehensive bibliographic database of published and unpublished literature relating to malaria in pregnancy
The Malaria Atlas Project provides maps of malaria transmission around the world
MedlinePlus provides links to additional information on malaria (in English and Spanish)
doi:10.1371/journal.pmed.1000221
PMCID: PMC2811150  PMID: 20126256
11.  Prescription Medicines and the Risk of Road Traffic Crashes: A French Registry-Based Study 
PLoS Medicine  2010;7(11):e1000366.
Using three nationwide databases in France, Ludivine Orriols, Emmanuel Lagarde, and colleagues provide evidence that prescribed medicines contribute to the risk of experiencing a road traffic crash.
Background
In recent decades, increased attention has been focused on the impact of disabilities and medicinal drug use on road safety. The aim of our study was to investigate the association between prescription medicines and the risk of road traffic crashes, and estimate the attributable fraction.
Methods and Findings
We extracted and matched data from three French nationwide databases: the national health care insurance database, police reports, and the national police database of injurious crashes. Drivers identified by their national health care number involved in an injurious crash in France, between July 2005 and May 2008, were included in the study. Medicines were grouped according to the four risk levels of the French classification system (from 0 [no risk] to 3 [high risk]). We included 72,685 drivers involved in injurious crashes. Users of level 2 (odds ratio [OR]  = 1.31 [1.24–1.40]) and level 3 (OR  = 1.25 [1.12–1.40]) prescription medicines were at higher risk of being responsible for a crash. The association remained after adjustment for the presence of a long-term chronic disease. The fraction of road traffic crashes attributable to levels 2 and 3 medications was 3.3% [2.7%–3.9%]. A within-person case-crossover analysis showed that drivers were more likely to be exposed to level 3 medications on the crash day than on a control day, 30 days earlier (OR  = 1.15 [1.05–1.27]).
Conclusion
The use of prescription medicines is associated with a substantial number of road traffic crashes in France. In light of the results, warning messages appear to be relevant for level 2 and 3 medications and questionable for level 1 medications. A follow-up study is needed to evaluate the impact of the warning labeling system on road traffic crash prevention.
Please see later in the article for the Editors' Summary
Editors' Summary
About 1.3 million people die each year on the world's road. 90% of road traffic deaths occur in developing countries, with pedestrians, cyclists, and users of two-wheel vehicles (scooters, motorbikes) the most vulnerable road users. Although the use of prescribed benzodiazepines has already been documented to be associated with road traffic accidents in industrialized countries, the effects of other medicines have not been well studied or have inconsistent results (for example opioids and antidepressant medications). In the European Union, it is mandatory for pharmaceutical companies to provide data about the effect of a medicine on ability to drive. In France, a multidisciplinary group of experts was appointed to classify all medicines into four levels of risk (from level 0, no or negligible risk, to level 3, major risk), in terms of their effect on driving performances. In 2006, the International Council on Alcohol, Drugs and Traffic Safety proposed a classification list similar to the French classification system.
Why Was This Study Done? There is a pressing need to understand the association between prescribed medicines and the risk of road traffic crashes and also to have a more accurate picture of the fraction of road traffic crashes that are attributable to the use of prescribed medicines. This large French study aimed to advance knowledge in this important area.
What Did the Researchers Do and Find? The researchers used three data sources to find the information they needed: the national health care insurance database (which covers the whole French population and includes data on reimbursed prescription medicines), police reports, and the national police database of injurious road traffic crashes. Drivers involved in road traffic crashes (identified by their national healthcare number) between July 2005 and May 2008 were included in the study. The researchers used a statistical model to conduct a responsibility analysis, which determined factors associated with each driver responsible for the road traffic crash and each driver who was not responsible (controls). In addition, the researchers compared medicine exposure during a period immediately before the crash (case period) with exposure during an earlier period (control period) for each driver involved in a crash. The researchers retrieved data on reimbursed medicines, dispensed within six months of the road traffic crash, by linking included drivers to the national health care insurance database using their national ID, gender, and date of birth and grouped all prescribed medicines according to the four risk levels of the French classification system.
During the study period, 72,685 drivers involved in injurious road traffic crashes were included. The researchers found that drivers who had been prescribed level 2 and level 3 medicines were at higher risk (odds ratio 1.31 and OR 1.25, respectively) of being responsible for the road traffic crash, an association that remained after the researchers adjusted for the presence of chronic diseases. Furthermore, the researchers found that the fraction of road traffic crashes attributable to the use of (prescriptions for) level 2 and 3 medicines was 3.3% and that drivers were more likely to be exposed to level 3 medicines on the day of the road traffic crash than on a control day.
What Do These Findings Mean? This study provides strong evidence for the contribution of medicines to the risk of experiencing a road traffic crash. The French drug risk classification scheme seems accurate for medicines classified as levels 2 and 3 of risk for road traffic crashes. The effect on driving abilities of level 2 medicines depends both on the pharmacodynamics of the drug and on individual susceptibility, whereas for level 3 medicines, the pharmacodynamic effect seems to be predominant. The effects of level 1 medicines seem to be so dependent on individual susceptibility that effects on driving abilities are rare, which raises questions about the relevance of the labels for these medicines. However, some limitations with the study methodology might affect the interpretation of these findings. For example, the researchers used dispensing dates for medications as a surrogate for ingestion and were not able to check for noncompliance.
However, this study provides some of the strongest evidence to date of the need for health care workers to provide patients with proper information on the potential effect of any medicine that they are prescribed (or take) on their driving abilities.
Additional Information Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000366.The World Health Organization (WHO) provides information on road traffic accidentsTwo Web sites provide information for drivers about drugs that could affect their ability to driveThe US National Institute on Drug Abuse of the National Institutes of Health has an information sheet on drugged driving
doi:10.1371/journal.pmed.1000366
PMCID: PMC2981588  PMID: 21125020
12.  Mortality among aircraft manufacturing workers 
OBJECTIVES: To evaluate the risk of cancer and other diseases among workers engaged in aircraft manufacturing and potentially exposed to compounds containing chromate, trichloroethylene (TCE), perchloroethylene (PCE), and mixed solvents. METHODS: A retrospective cohort mortality study was conducted of workers employed for at least 1 year at a large aircraft manufacturing facility in California on or after 1 January 1960. The mortality experience of these workers was determined by examination of national, state, and company records to the end of 1996. Standardised mortality ratios (SMRs) were evaluated comparing the observed numbers of deaths among workers with those expected in the general population adjusting for age, sex, race, and calendar year. The SMRs for 40 cause of death categories were computed for the total cohort and for subgroups defined by sex, race, position in the factory, work duration, year of first employment, latency, and broad occupational groups. Factory job titles were classified as to likely use of chemicals, and internal Poisson regression analyses were used to compute mortality risk ratios for categories of years of exposure to chromate, TCE, PCE, and mixed solvents, with unexposed factory workers serving as referents. RESULTS: The study cohort comprised 77,965 workers who accrued nearly 1.9 million person-years of follow up (mean 24.2 years). Mortality follow up, estimated as 99% complete, showed that 20,236 workers had died by 31 December 1996, with cause of death obtained for 98%. Workers experienced low overall mortality (all causes of death SMR 0.83) and low cancer mortality (SMR 0.90). No significant increases in risk were found for any of the 40 specific cause of death categories, whereas for several causes the numbers of deaths were significantly below expectation. Analyses by occupational group and specific job titles showed no remarkable mortality patterns. Factory workers estimated to have been routinely exposed to chromate were not at increased risk of total cancer (SMR 0.93) or of lung cancer (SMR 1.02). Workers routinely exposed to TCE, PCE, or a mixture of solvents also were not at increased risk of total cancer (SMRs 0.86, 1.07, and 0.89, respectively), and the numbers of deaths for specific cancer sites were close to expected values. Slight to moderately increased rates of non-Hodgkin's lymphoma were found among workers exposed to TCE or PCE, but none was significant. A significant increase in testicular cancer was found among those with exposure to mixed solvents, but the excess was based on only six deaths and could not be linked to any particular solvent or job activity. Internal cohort analyses showed no significant trends of increased risk for any cancer with increasing years of exposure to chromate or solvents. CONCLUSIONS: The results from this large scale cohort study of workers followed up for over 3 decades provide no clear evidence that occupational exposures at the aircraft manufacturing factory resulted in increases in the risk of death from cancer or other diseases. Our findings support previous studies of aircraft workers in which cancer risks were generally at or below expected levels.
 
PMCID: PMC1757791  PMID: 10615290
13.  Self-reported occupational exposure to HIV and factors influencing its management practice: a study of healthcare workers in Tumbi and Dodoma Hospitals, Tanzania 
Background
Blood borne infectious agents such as hepatitis B virus (HBV), hepatitis C virus (HCV) and human immune deficiency virus (HIV) constitute a major occupational hazard for healthcare workers (HCWs). To some degree it is inevitable that HCWs sustain injuries from sharp objects such as needles, scalpels and splintered bone during execution of their duties. However, in Tanzania, there is little or no information on factors that influence the practice of managing occupational exposure to HIV by HCWs. This study was conducted to determine the prevalence of self-reported occupational exposure to HIV among HCWs and explore factors that influence the practice of managing occupational exposure to HIV by HCWs in Tanzania.
Methods
Self-administered questionnaire was designed to gather information of healthcare workers’ occupational exposures in the past 12 months and circumstances in which these injuries occurred. Practice of managing occupational exposure was assessed by the following questions:
Results
Nearly half of the HCWs had experienced at least one occupational injury in the past 12 months. Though most of the occupational exposures to HIV were experienced by female nurses, non-medical hospital staff received PEP more frequently than nurses and doctors. Doctors and nurses frequently encountered occupational injuries in surgery room and labor room respectively. HCWs with knowledge on the possibility of HIV transmission and those who knew whom to contact in event of occupational exposure to HIV were less likely to have poor practice of managing occupational exposure.
Conclusion
Needle stick injuries and splashes are common among HCWs at Tumbi and Dodoma hospitals. Knowledge of the risk of HIV transmission due to occupational exposure and knowing whom to contact in event of exposure predicted practice of managing the exposure. Thus provision of health education on occupational exposure may strengthen healthcare workers’ practices to manage occupational exposure.
doi:10.1186/1472-6963-13-276
PMCID: PMC3718638  PMID: 23866940
HIV; Occupational exposure; Healthcare workers
14.  Attitudes of healthcare workers in U.S. hospitals regarding smallpox vaccination 
BMC Public Health  2003;3:20.
Background
The United States is implementing plans to immunize 500,000 hospital-based healthcare workers against smallpox. Vaccination is voluntary, and it is unknown what factors drive vaccine acceptance. This study's aims were to estimate the proportion of workers willing to accept vaccination and to identify factors likely to influence their decisions.
Methods
The survey was conducted among physicians, nurses, and others working primarily in emergency departments or intensive care units at 21 acute-care hospitals in 10 states during the two weeks before the U.S. national immunization program for healthcare workers was announced in December 2002. Of the questionnaires distributed, 1,165 were returned, for a response rate of 81%. The data were analyzed by logistic regression and were adjusted for clustering within hospital and for different number of responses per hospital, using generalized linear mixed models and SAS's NLMIXED procedure.
Results
Sixty-one percent of respondents said they would definitely or probably be vaccinated, while 39% were undecided or inclined against it. Fifty-three percent rated the risk of a bioterrorist attack using smallpox in the United States in the next two years as either intermediate or high. Forty-seven percent did not feel well-informed about the risks and benefits of vaccination. Principal concerns were adverse reactions and the risk of transmitting vaccinia. In multivariate analysis, four variables were associated with willingness to be vaccinated: perceived risk of an attack, self-assessed knowledge about smallpox vaccination, self-assessed previous smallpox vaccination status, and gender.
Conclusions
The success of smallpox vaccination efforts will ultimately depend on the relative weight in people's minds of the risk of vaccine adverse events compared with the risk of being exposed to the disease. Although more than half of the respondents thought the likelihood of a bioterrorist smallpox attack was intermediate or high, less than 10% of the group slated for vaccination has actually accepted it at this time. Unless new information about the threat of a smallpox attack becomes available, healthcare workers' perceptions of the vaccine's risks will likely continue to drive their ongoing decisions about smallpox vaccination.
doi:10.1186/1471-2458-3-20
PMCID: PMC165598  PMID: 12801426
15.  Reported incidence of occupational asthma in the United Kingdom, 1989-97 
OBJECTIVES—To examine trends in estimated population based incidence of occupational asthma by age, sex, occupation, geographical region, and causal agents based on 9 years of the Surveillance of Work Related and Occupational Respiratory Disease (SWORD) data.
METHODS—In January 1989 the SWORD scheme for the surveillance of occupational respiratory disease was established in the United Kingdom to make good the lack of epidemiological information on the incidence of these diseases in the United Kingdom. Between 80% and 90% of chest and occupational physicians report voluntarily all new cases they see, on a monthly or random sampling basis. During the 9 years 1989-97, an estimated 25 674 new cases of occupational respiratory disease, including 7387 of occupational asthma, were reported. Suspected causal agents were classified into 44 categories and estimated annual incidences of asthma were calculated with denominators from the labour force survey.
RESULTS—Overall, a third of the suspected causes of asthma were organic, a third chemical, 6% metallic, and the rest miscellaneous, or in 8%, unknown. There was evidence of an increase since 1989 in cases due to latex, and possibly glutaraldehyde, and an apparent drop since 1991 in the proportion of cases attributed to isocyanates. Incidences were higher in men than women and the disparity was especially marked in the population aged 45 years or more in which rates for men were at least twice those for women. Average annual rates per million workers for 1992-7 ranged from 7 (95% confidence interval (95% CI) 5 to 9) for the lowest risk group of professional, clerical, and service workers to 1464 (95% CI 968 to 2173) for coach and other spray painters. Except for laboratory technicians, all other occupations with rates over 100 were concerned with manufacturing and processing that used chemicals, metals, and organic materials. Incidences were two to three times higher in the north and midlands than in East Anglia and the south. The introduction of a sampling scheme in 1992 doubled estimates of reported incidence of occupational asthma, but there was little evidence of other temporal changes.
CONCLUSIONS—The SWORD scheme has produced consistent estimates of the causes and incidence of occupational asthma as seen by chest and occupational physicians. It has allowed the epidemiology of occupational asthma in the population to be studied and high risk occupations to be identified. There is certainly more occupational asthma in the population than that which reaches specialists in occupational and chest medicine; therefore the incidence rates presented here are underestimates, but by how much remains unknown.


Keywords: occupational asthma; incidence; regional differences
doi:10.1136/oem.57.12.823
PMCID: PMC1739897  PMID: 11077011
16.  A Collaborative Epidemiological Investigation into the Criminal Fake Artesunate Trade in South East Asia  
PLoS Medicine  2008;5(2):e32.
Background
Since 1998 the serious public health problem in South East Asia of counterfeit artesunate, containing no or subtherapeutic amounts of the active antimalarial ingredient, has led to deaths from untreated malaria, reduced confidence in this vital drug, large economic losses for the legitimate manufacturers, and concerns that artemisinin resistance might be engendered.
Methods and Findings
With evidence of a deteriorating situation, a group of police, criminal analysts, chemists, palynologists, and health workers collaborated to determine the source of these counterfeits under the auspices of the International Criminal Police Organization (INTERPOL) and the Western Pacific World Health Organization Regional Office. A total of 391 samples of genuine and counterfeit artesunate collected in Vietnam (75), Cambodia (48), Lao PDR (115), Myanmar (Burma) (137) and the Thai/Myanmar border (16), were available for analysis. Sixteen different fake hologram types were identified. High-performance liquid chromatography and/or mass spectrometry confirmed that all specimens thought to be counterfeit (195/391, 49.9%) on the basis of packaging contained no or small quantities of artesunate (up to 12 mg per tablet as opposed to ∼ 50 mg per genuine tablet). Chemical analysis demonstrated a wide diversity of wrong active ingredients, including banned pharmaceuticals, such as metamizole, and safrole, a carcinogen, and raw material for manufacture of methylenedioxymethamphetamine (‘ecstasy'). Evidence from chemical, mineralogical, biological, and packaging analysis suggested that at least some of the counterfeits were manufactured in southeast People's Republic of China. This evidence prompted the Chinese Government to act quickly against the criminal traders with arrests and seizures.
Conclusions
An international multi-disciplinary group obtained evidence that some of the counterfeit artesunate was manufactured in China, and this prompted a criminal investigation. International cross-disciplinary collaborations may be appropriate in the investigation of other serious counterfeit medicine public health problems elsewhere, but strengthening of international collaborations and forensic and drug regulatory authority capacity will be required.
Paul Newton and colleagues' international, collaborative study found evidence that counterfeit artesunate was being manufactured in China, which prompted a criminal investigation.
Editors' Summary
Background
Malaria is one of the world's largest public health problems, causing around 500 million cases of illness and at least one million deaths per year (the estimates vary widely). The most serious form of malaria is caused by the parasite Plasmodium falciparum, which has become resistant to multiple drugs that had previously been the cornerstones of antimalarial regimens. One group of drugs for treating malaria, the artemisinin therapies including artesunate, are based upon a Chinese herb called qinghaosu; these have now become vital to the treatment of P. falciparum malaria. But counterfeit artesunate, containing none or too little (“subtherapeutic levels”) of the active ingredient, is a growing problem especially in South and East Asia. Fake artesunate is devastating for malaria control: it causes avoidable death, reduces confidence in the drug, and takes away profit from legitimate manufacturers. Of major concern also is the potential for subtherapeutic counterfeit artesunate to fuel the parasite's resistance to the artemisinin group of drugs.
Previous estimates have suggested that between 33% and 53% of artesunate tablets in mainland South East Asia are counterfeit. In this paper the authors report on an unprecedented international collaboration and criminal investigation that attempted to quantify and source counterfeit artesunate among some of the most malarious countries in Asia.
Why Was This Study Done?
Previous reports have identified the problem of fake artesunate, but as of yet there have been few reports on the potential solutions. Concerned health workers and scientists, the regional World Health Organization (WHO) office and the International Criminal Police Organization (INTERPOL) got together to discuss what could be done in May 2005 when it became clear the counterfeit artesunate situation was worsening in the Greater Mekong Sub-Region of South East Asia (comprising Cambodia, Lao People's Democratic Republic, Myanmar, Thailand, Vietnam, and Yunnan Province in the People's Republic of China). Their subsequent investigation combined the goals and methods of a range of concerned parties—police, scientists, and health workers—to identify the source of counterfeit artesunate in South East Asia and to supply the evidence to help arrest and prosecute the perpetrators.
What Did the Researchers Do and Find?
The researchers conducted forensic analyses of samples of genuine and counterfeit artesunate. They selected these samples from larger surveys and investigations that had been conducted in the region beginning in the year 2000. Genuine samples were supplied by a manufacturer to provide a comparator. The authors examined the physical appearance of the packages and subjected the tablets to a wide range of chemical and biological tests that allowed an analysis of the components contained in the tablets.
When comparing the collected packages and tablets against the genuine samples, the researchers found considerable diversity of fake artesunate in SE Asia. Sixteen different fake hologram types (the stickers contained on packages meant to identify them as genuine) were found. Chemical analysis revealed that all tablets thought to be fake contained no or very small quantities of artesunate. Other ingredients found in the artesunate counterfeit tablets included paracetamol, antibiotics, older antimalarial drugs, and a range of minerals, and there were a variety of gases surrounding the tablets inside the packaging. Biological analyses of pollen grains inside the packaging suggested that the packages originated in the parts of South East Asia along the Chinese border.
What Do these Findings Mean?
The results were crucial in helping the authorities establish the origin of the fake artesunate. For example, the authors identified two regional clusters where the counterfeit tablets appeared to be coming from, thus flagging a potential manufacturing site or distribution network. The presence of wrong active pharmaceutical ingredients (such as the older antimalarial drugs) suggested the counterfeiters had access to a variety of active pharmaceutical ingredients. The presence of safrole, a precursor to the illicit drug ecstasy, suggested the counterfeits may be coming from factories that manufacture ecstasy. And the identification of minerals indigenous to certain regions also helped identify the counterfeits' origin. The researchers concluded that at least some of the counterfeit artesunate was coming from southern China. The Secretary General of INTERPOL presented the findings to the Chinese government, which then carried out a criminal investigation and arrested individuals alleged to have produced and distributed the counterfeit artesunate.
The collaboration between police, public health workers and scientists on combating fake artesunate is unique, and provides a model for others to follow. However, the authors note that substantial capacity in forensic analysis and the infrastructure to support collaborations between these different disciplines are needed.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050032.
The World Health Organization in 2006 created IMPACT—International Medical Products Anti-Counterfeiting Taskforce—with the aim of forging international collaboration to seek global solutions to this global challenge and in raising awareness of the dangers of counterfeit medical products. The task force membership includes international organizations, nongovernmental organizations, enforcement agencies, pharmaceutical manufacturers' associations, and drug and regulatory authorities. IMPACT's Web site notes that trade in counterfeit medicines is widespread and affects both developed and developing countries but is more prevalent in countries that have weak drug regulatory systems, poor supply of basic medicines, unregulated markets, high drug prices and/or significant price differentials. IMPACT holds international conferences and maintains a rapid alert system for counterfeit drugs.
The drug industry's anticounterfeit organization, Pharmaceutical Security Institute, works to develop improved systems to identify the extent of the counterfeiting problem and to assist in coordinating international inquiries. Its membership includes 21 large pharmaceutical companies.
The Web site of David Pizzanelli, a world expert on security holography, contains a PowerPoint presentation co-authored by Paul Newton that illustrates the different types of fake holograms found on fake artesunate packages, and their implications for artemisinin resistance (http://www.pizzanelli.co.uk/content/artesunate.html).
doi:10.1371/journal.pmed.0050032
PMCID: PMC2235893  PMID: 18271620
17.  Rates of Latent Tuberculosis in Health Care Staff in Russia 
PLoS Medicine  2007;4(2):e55.
Background
Russia is one of 22 high burden tuberculosis (TB) countries. Identifying individuals, particularly health care workers (HCWs) with latent tuberculosis infection (LTBI), and determining the rate of infection, can assist TB control through chemoprophylaxis and improving institutional cross-infection strategies. The objective of the study was to estimate the prevalence and determine the relative risks and risk factors for infection, within a vertically organised TB service in a country with universal bacille Calmette-Guérin (BCG) vaccination.
Methods and Findings
We conducted a cross-sectional study to assess the prevalence of and risk factors for LTBI among unexposed students, minimally exposed medical students, primary care health providers, and TB hospital health providers in Samara, Russian Federation. We used a novel in vitro assay (for gamma-interferon [IFN-γ]) release to establish LTBI and a questionnaire to address risk factors. LTBI was seen in 40.8% (107/262) of staff and was significantly higher in doctors and nurses (39.1% [90/230]) than in students (8.7% [32/368]) (relative risk [RR] 4.5; 95% confidence interval [CI] 3.1–6.5) and in TB service versus primary health doctors and nurses: respectively 46.9% (45/96) versus 29.3% (34/116) (RR 1.6; 95% CI 1.1–2.3). There was a gradient of LTBI, proportional to exposure, in medical students, primary health care providers, and TB doctors: respectively, 10.1% (24/238), 25.5% (14/55), and 55% (22/40). LTBI was also high in TB laboratory workers: 11/18 (61.1%).
Conclusions
IFN-γ assays have a useful role in screening HCWs with a high risk of LTBI and who are BCG vaccinated. TB HCWs were at significantly higher risk of having LTBI. Larger cohort studies are needed to evaluate the individual risks of active TB development in positive individuals and the effectiveness of preventive therapy based on IFN-γ test results.
Gamma-interferon assays were used in a cross-sectional study of Russian health care workers and found high rates of latent tuberculosis infection.
Editors' Summary
Background.
Tuberculosis (TB) is a very common and life-threatening infection caused by a bacterium, Mycobacterium tuberculosis, which is carried by about a third of the world's population. Many people who are infected do not develop the symptoms of disease; this is called “latent infection.” However, it is important to detect latent infection among people in high-risk communities, in order to prevent infected people from developing active disease, and therefore also reduce the spread of TB within the community. 22 countries account for 80% of the world's active TB, and Russia is one of these. Health care workers are particularly at risk for developing active TB disease in Russia, but the extent of latent infection is not known. In order to design appropriate measures for controlling TB in Russia, it is important to know how common latent infection is among health care workers, as well as other members of the community.
Why Was This Study Done?
The researchers here had been studying the spread of tuberculosis in Samara City in southeastern Russia, where the rate of TB disease among health care workers was very high; in 2004 the number of TB cases among health care workers on TB wards was over ten times that in the general population. There was also no information available on the rates of latent TB infection among health care workers in Samara City. The researchers therefore wanted to work out what proportion of health care workers in Samara City had latent TB infection, and particularly to compare groups whom they thought would be at different levels of risk (students, clinicians outside of TB wards, clinicians on TB wards, etc.). Finally, the researchers also wanted to use a new test for detecting latent TB infection. The traditional test for detecting TB infection (tuberculin skin test) is not very reliable among people who have received the Bacillus Calmette-Guérin (BCG) vaccination against TB earlier in life, as is the case in Russia. In this study a new test was therefore used, based on measuring the immune response to two proteins produced by M. tuberculosis, which are not present in the BCG vaccine strain.
What Did the Researchers Do and Find?
In this study the researchers tested health care workers from all the TB clinics in Samara City, as well as other clinical staff and students, for latent tuberculosis. In total, 630 people had blood samples taken for testing. A questionnaire was also used to collect information on possible risk factors for TB. As expected, the rate of latent TB infection was highest among clinical staff working in the TB clinics, 47% of whom were infected with M. tuberculosis. This compared to a 10% infection rate among medical students and 29% infection rate among primary care health workers. The differences in infection rate between medical students, primary care health workers, and TB clinic staff were statistically significant and reflected progressively increasing exposure to TB. Among primary care health workers, past exposure to TB was a risk factor for having latent TB infection.
What Do These Findings Mean?
This study showed that there was a high rate of latent TB infection among health care workers in Samara City and that infection is increasingly likely among people with either past or present exposure to TB. The results suggest that further research should be carried out to test whether mass screening for latent infection, followed by treatment, will reduce the rate of active TB disease among health care workers and also prevent further spread of TB. There are concerns that widespread treatment of latent infection may not be completely effective due to the relatively high prevalence of drug-resistant TB strains and any new initiatives would therefore need to be carefully evaluated.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0040055.
The Stop TB Partnership has been set up to eliminate TB as a public health problem; its site provides data and resources about TB in each of the 22 most-affected countries, including Russia
Tuberculosis minisite from the World Health Organization, providing data on tuberculosis worldwide, details of the Stop TB strategy, as well as fact sheets and current guidelines
The US Centers for Disease Control has a tuberculosis minisite, including a fact sheet on latent TB
Information from the US Centers for Disease Control about the QuantiFERON-TB Gold test, used to test for latent TB infection in this study
doi:10.1371/journal.pmed.0040055
PMCID: PMC1796908  PMID: 17298167
18.  Global Estimates of the Burden of Injury and Illness at Work in 2012 
This article reviews the present indicators, trends, and recent solutions and strategies to tackle major global and country problems in safety and health at work. The article is based on the Yant Award Lecture of the American Industrial Hygiene Association (AIHA) at its 2013 Congress. We reviewed employment figures, mortality rates, occupational burden of disease and injuries, reported accidents, surveys on self-reported occupational illnesses and injuries, attributable fractions, national economic cost estimates of work-related injuries and ill health, and the most recent information on the problems from published papers, documents, and electronic data sources of international and regional organizations, in particular the International Labor Organization (ILO), World Health Organization (WHO), and European Union (EU), institutions, agencies, and public websites. We identified and analyzed successful solutions, programs, and strategies to reduce the work-related negative outcomes at various levels. Work-related illnesses that have a long latency period and are linked to ageing are clearly on the increase, while the number of occupational injuries has gone down in industrialized countries thanks to both better prevention and structural changes. We have estimated that globally there are 2.3 million deaths annually for reasons attributed to work. The biggest component is linked to work-related diseases, 2.0 million, and 0.3 million linked to occupational injuries. However, the division of these two factors varies depending on the level of development. In industrialized countries the share of deaths caused by occupational injuries and work-related communicable diseases is very low while non-communicable diseases are the overwhelming causes in those countries. Economic costs of work-related injury and illness vary between 1.8 and 6.0% of GDP in country estimates, the average being 4% according to the ILO. Singapore's economic costs were estimated to be equivalent to 3.2% of GDP based on a preliminary study. If economic losses would take into account involuntary early retirement then costs may be considerably higher, for example, in Finland up to 15% of GDP, while this estimate covers various disorders where work and working conditions may be just one factor of many or where work may aggravate the disease, injury, or disorders, such as traffic injuries, mental disorders, alcoholism, and genetically induced problems. Workplace health promotion, services, and safety and health management, however, may have a major preventive impact on those as well. Leadership and management at all levels, and engagement of workers are key issues in changing the workplace culture. Vision Zero is a useful concept and philosophy in gradually eliminating any harm at work. Legal and enforcement measures that themselves support companies and organizations need to be supplemented with economic justification and convincing arguments to reduce corner-cutting in risk management, and to avoid short- and long-term disabilities, premature retirement, and corporate closures due to mismanagement and poor and unsustainable work life. We consider that a new paradigm is needed where good work is not just considered a daily activity. We need to foster stable conditions and circumstances and sustainable work life where the objective is to maintain your health and work ability beyond the legal retirement age. We need safe and healthy work, for life.
doi:10.1080/15459624.2013.863131
PMCID: PMC4003859  PMID: 24219404
burden of injury and illness at work; global estimates; mortality; occupational accidents; occupational exposures; work-related disease
19.  Mortality from lung cancer and population risk attributable to asbestos in an asbestos cement manufacturing town in Italy 
OBJECTIVE: To estimate mortality from lung cancer and the risk attributable to asbestos separately for asbestos cement workers and for the general (non-occupationally exposed) population in the town of Casale Monferrato, where the largest Italian asbestos cement factory had been in operation in 1907-86. According to cancer registry data, in the same town the incidence of malignant mesothelioma in the general population is about 10 times higher than in comparable Italian provinces. METHOD: Decedents from lung cancer in 1989-95 were nominally identified in the list of decedents kept at the Local Health Authority of Casale Monferrato. Workers in the asbestos cement factory have been identified with a search in the nominal list of workers and the same was done for the wives of asbestos cement workers. These lists have already been used in cohort studies. Sensitivity and specificity of the linkage procedure with occupational activity in asbestos cement production have been evaluated in a previous study. Population at risk was estimated on the basis of official figures and on the results of the cohort study of asbestos cement workers. RESULTS: 227 deaths from lung cancer were included (184 men and 43 women). Among the asbestos cement workers mortalities were 234.0 x 100,000 person-years among men and 35.5 among women. Corresponding figures in the general (non- occupationally exposed) population in Casale Monferrato were 80.6 and 18.7. The rates in the general population were not higher than in the rest of the region. Attributable risk (AR) among the asbestos cement workers (and wives) is 67.5% (95% confidence interval (95% CI) 56.8 to 78.2) for men and 51.3% (95% CI 14.9 to 87.8) among women. Population AR to occupational or paraoccupational exposure in the asbestos cement production is 18.3% (95% CI 11.1 to 25.6) among men and 10.1% (95% CI 0 to 24.6) among women. CONCLUSION: This work did not show an increase in mortality from lung cancer for the population not exposed occupationally, but a large excess was found among men and women occupationally exposed in asbestos cement production. The total burden of lung cancer due to occupational exposure to asbestos may be underestimated, as only occupational exposure in asbestos cement production was taken into consideration. Nevertheless even a single factory can be responsible for a considerable proportion of deaths from lung cancer in a population.
 
PMCID: PMC1757553  PMID: 9614395
20.  Community Mobilization in Mumbai Slums to Improve Perinatal Care and Outcomes: A Cluster Randomized Controlled Trial 
PLoS Medicine  2012;9(7):e1001257.
David Osrin and colleagues report findings from a cluster-randomized trial conducted in Mumbai slums; the trial aimed to evaluate whether facilitator-supported women's groups could improve perinatal outcomes.
Introduction
Improving maternal and newborn health in low-income settings requires both health service and community action. Previous community initiatives have been predominantly rural, but India is urbanizing. While working to improve health service quality, we tested an intervention in which urban slum-dweller women's groups worked to improve local perinatal health.
Methods and Findings
A cluster randomized controlled trial in 24 intervention and 24 control settlements covered a population of 283,000. In each intervention cluster, a facilitator supported women's groups through an action learning cycle in which they discussed perinatal experiences, improved their knowledge, and took local action. We monitored births, stillbirths, and neonatal deaths, and interviewed mothers at 6 weeks postpartum. The primary outcomes described perinatal care, maternal morbidity, and extended perinatal mortality. The analysis included 18,197 births over 3 years from 2006 to 2009. We found no differences between trial arms in uptake of antenatal care, reported work, rest, and diet in later pregnancy, institutional delivery, early and exclusive breastfeeding, or care-seeking. The stillbirth rate was non-significantly lower in the intervention arm (odds ratio 0.86, 95% CI 0.60–1.22), and the neonatal mortality rate higher (1.48, 1.06–2.08). The extended perinatal mortality rate did not differ between arms (1.19, 0.90–1.57). We have no evidence that these differences could be explained by the intervention.
Conclusions
Facilitating urban community groups was feasible, and there was evidence of behaviour change, but we did not see population-level effects on health care or mortality. In cities with multiple sources of health care, but inequitable access to services, community mobilization should be integrated with attempts to deliver services for the poorest and most vulnerable, and with initiatives to improve quality of care in both public and private sectors.
Trial registration
Current Controlled Trials ISRCTN96256793
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Substantial progress is being made to reduce global child mortality (deaths of children before the age of 5 years) and maternal mortality (deaths among women because of complications of pregnancy and childbirth)—two of the Millennium Development Goals agreed by world leaders in 2000 to end extreme poverty. Even so, worldwide, in 2010, 7.6 million children died before their fifth birthday and there were nearly 360,000 maternal deaths. Almost all child and maternal deaths occur in developing countries—a fifth of under-five deaths and more than a quarter of neonatal deaths (deaths during the first month of life, which account for two-fifths of all child deaths) occur in India alone. Moreover, most child and maternal deaths are caused by avoidable conditions. Specifically, the major causes of neonatal death—complications of preterm delivery, breathing problems during or after delivery, and infections of the blood (sepsis) and lungs (pneumonia)—and of maternal deaths—hemorrhage (abnormal bleeding), sepsis, unsafe abortion, obstructed labor, and hypertensive diseases of pregnancy—could all be largely prevented by improved access to reproductive health services and skilled health care workers.
Why Was This Study Done?
Experts believe that improvements to maternal and newborn health in low-income settings require both health service strengthening and community action. That is, the demand for better services, driven by improved knowledge about maternal and newborn health (perinatal issues), has to be increased in parallel with the supply of those services. To date, community mobilization around perinatal issues has largely been undertaken in rural settings but populations in developing countries are becoming increasingly urban. In India, for example, 30% of the population now lives in cities. In this cluster randomized controlled trial (a study in which groups of people are randomly assigned to receive alternative interventions and the outcomes in the differently treated “clusters” are compared), City Initiative for Newborn Health (CINH) researchers investigate the effect of an intervention designed to help women's groups in the slums of Mumbai work towards improving local perinatal health. The CINH aims to improve maternal and newborn health in slum communities by improving public health care provision and by working with community members to improve maternal and newborn care practices and care-seeking behaviors.
What Did the Researchers Do and Find?
The researchers enrolled 48 Mumbai slum communities of at least 1,000 households into their trial. In each of the 24 intervention clusters, a facilitator supported local women's groups through a 36-meeting learning cycle during which group members discussed their perinatal experiences, improved their knowledge, and took action. To measure the effect of the intervention, the researchers monitored births, stillbirths, and neonatal deaths in all the clusters and interviewed mothers 6 weeks after delivery. During the 3-year trial, there were 18,197 births in the participating settlements. The women in the intervention clusters were enthusiastic about acquiring new knowledge and made substantial efforts to reach out to other women but were less successful in undertaking collective action such as negotiations with civic authorities for more amenities. There were no differences between the intervention and control communities in the uptake of antenatal care, reported work, rest, and diet in late pregnancy, institutional delivery, or in breast feeding and care-seeking behavior. Finally, the combined rate of stillbirths and neonatal deaths (the extended perinatal mortality rate) was the same in both arms of the trial, as was maternal mortality.
What Do These Findings Mean?
These findings indicate that it is possible to facilitate the discussion of perinatal health care by urban women's groups in the challenging conditions that exist in the slums of Mumbai. However, they fail to show any measureable effect of community mobilization through the facilitation of women's groups on perinatal health at the population level. The researchers acknowledge that more intensive community activities that target the poorest, most vulnerable slum dwellers might produce measurable effects on perinatal mortality, and they conclude that, in cities with multiple sources of health care and inequitable access to services, it remains important to integrate community mobilization with attempts to deliver services to the poorest and most vulnerable, and with initiatives to improve the quality of health care in both the public and private sector.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001257.
The United Nations Childrens Fund (UNICEF) works for children's rights, survival, development, and protection around the world; it provides information on the reduction of child mortality (Millennium Development Goal 4); its Childinfo website provides information about all the Millennium Development Goals and detailed statistics about on child survival and health, newborn care, and maternal health (some information in several languages)
The World Health Organization also has information about Millennium Development Goal 4 and Millennium Development Goal 5, the reduction of maternal mortality, provides information on newborn infants, and provides estimates of child mortality rates (some information in several languages)
Further information about the Millennium Development Goals is available
Information on the City Initiative for Newborn Health and its partners and a detailed description of its trial of community mobilization in Mumbai slums to improve care during pregnancy, delivery, postnatally and for the newborn are available
Further information about the Society for Nutrition, Education and Health Action (SNEHA) is available
doi:10.1371/journal.pmed.1001257
PMCID: PMC3389036  PMID: 22802737
21.  The Effects of Influenza Vaccination of Health Care Workers in Nursing Homes: Insights from a Mathematical Model 
PLoS Medicine  2008;5(10):e200.
Background
Annual influenza vaccination of institutional health care workers (HCWs) is advised in most Western countries, but adherence to this recommendation is generally low. Although protective effects of this intervention for nursing home patients have been demonstrated in some clinical trials, the exact relationship between increased vaccine uptake among HCWs and protection of patients remains unknown owing to variations between study designs, settings, intensity of influenza seasons, and failure to control all effect modifiers. Therefore, we use a mathematical model to estimate the effects of HCW vaccination in different scenarios and to identify a herd immunity threshold in a nursing home department.
Methods and Findings
We use a stochastic individual-based model with discrete time intervals to simulate influenza virus transmission in a 30-bed long-term care nursing home department. We simulate different levels of HCW vaccine uptake and study the effect on influenza virus attack rates among patients for different institutional and seasonal scenarios. Our model reveals a robust linear relationship between the number of HCWs vaccinated and the expected number of influenza virus infections among patients. In a realistic scenario, approximately 60% of influenza virus infections among patients can be prevented when the HCW vaccination rate increases from 0 to 1. A threshold for herd immunity is not detected. Due to stochastic variations, the differences in patient attack rates between departments are high and large outbreaks can occur for every level of HCW vaccine uptake.
Conclusions
The absence of herd immunity in nursing homes implies that vaccination of every additional HCW protects an additional fraction of patients. Because of large stochastic variations, results of small-sized clinical trials on the effects of HCW vaccination should be interpreted with great care. Moreover, the large variations in attack rates should be taken into account when designing future studies.
Using a mathematical model to simulate influenza transmission in nursing homes, Carline van den Dool and colleagues find that each additional staff member vaccinated further reduces the risk to patients.
Editors' Summary
Background.
Every winter, millions of people catch influenza, a contagious viral disease of the nose, throat, and airways. Most people recover completely from influenza within a week or two but some develop life-threatening complications such as bacterial pneumonia. As a result, influenza outbreaks kill about half a million people—mainly infants, elderly people, and chronically ill individuals—each year. To minimize influenza-related deaths, the World Health Organization recommends that vulnerable people be vaccinated against influenza every autumn. Annual vaccination is necessary because flu viruses continually make small changes to the viral proteins (antigens) that the immune system recognizes. This means that an immune response produced one year provides only partial protection against influenza the next year. To provide maximum protection against influenza, each year's vaccine contains disabled versions of the major circulating strains of influenza viruses.
Why Was This Study Done?
Most Western countries also recommend annual flu vaccination for health care workers (HCWs) in hospitals and other institutions to reduce the transmission of influenza to vulnerable patients. However, many HCWs don't get a regular flu shot, so should efforts be made to increase their rate of vaccine uptake? To answer this question, public-health experts need to know more about the relationship between vaccine uptake among HCWs and patient protection. In particular, they need to know whether a high rate of vaccine uptake by HCWs will provide “herd immunity.” Herd immunity occurs because, when a sufficient fraction of a population is immune to a disease that passes from person to person, infected people rarely come into contact with susceptible people, which means that both vaccinated and unvaccinated people are protected from the disease. In this study, the researchers develop a mathematical model to investigate the relationship between vaccine uptake among HCWs and patient protection in a nursing home department.
What Did the Researchers Do and Find?
To predict influenza virus attack rates (the number of patient infections divided by the number of patients in a nursing home department during an influenza season) at different levels of HCW vaccine uptake, the researchers develop a stochastic transmission model to simulate epidemics on a computer. This model predicts that as the HCW vaccination rate increases from 0 (no HCWs vaccinated) to 1 (all the HCWs vaccinated), the expected average influenza virus attack rate decreases at a constant rate. In the researchers' baseline scenario—a nursing home department with 30 beds where patients come into contact with other patients, HCWs, and visitors—the model predicts that about 60% of the patients who would have been infected if no HCWs had been vaccinated are protected when all the HCWs are vaccinated, and that seven HCWs would have to be vaccinated to protect one patient. This last figure does not change with increasing vaccine uptake, which indicates that there is no level of HCW vaccination that completely stops the spread of influenza among the patients; that is, there is no herd immunity. Finally, the researchers show that large influenza outbreaks can happen by chance at every level of HCW vaccine uptake.
What Do These Findings Mean?
As with all mathematical models, the accuracy of these predictions may depend on the specific assumptions built into the model. Therefore the researchers verified that their findings hold for a wide range of plausible assumptions. These findings have two important practical implications. First, the direct relationship between HCW vaccination and patient protection and the lack of any herd immunity suggest that any increase in HCW vaccine uptake will be beneficial to patients in nursing homes. That is, increasing the HCW vaccination rate from 80% to 90% is likely to be as important as increasing it from 10% to 20%. Second, even 100% HCW vaccination cannot guarantee that influenza outbreaks will not occasionally occur in nursing homes. Because of the large variation in attack rates, the results of small clinical trials on the effects of HCW vaccination may be inaccurate and future studies will need to be very large if they are to provide reliable estimates of the amount of protection that HCW vaccination provides to vulnerable patients.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050200.
Read the related PLoSMedicine Perspective by Cécile Viboud and Mark Miller
A related PLoSMedicine Research Article by Jeffrey Kwong and colleagues is also available
The World Health Organization provides information on influenza and on influenza vaccines (in several languages)
The US Centers for Disease Control and Prevention provide information for patients and professionals on all aspects of influenza (in English and Spanish)
The UK Health Protection Agency also provides information on influenza
MedlinePlus provides a list of links to other information about influenza (in English and Spanish)
The UK National Health Service provides information about herd immunity, including a simple explanatory animation
The European Centre for Disease Prevention and Control provides an overview on the types of influenza
doi:10.1371/journal.pmed.0050200
PMCID: PMC2573905  PMID: 18959470
22.  Awareness and risk perception of hepatitis B infection among auxiliary healthcare workers 
Context:
Auxiliary healthcare workers (AHCWs) have a higher risk of occupational exposure to hepatitis B virus infection than the general population. Daily handling and exposure to biomedical wastes, blood, and its products make the AHCWs vulnerable to blood borne diseases among which Hepatitis B is one of the world's most common and serious infectious diseases.
Aims:
To evaluate the HBV infection related awareness and occupational risk perception among AHCWs.
Settings and Design:
Survey.
Materials and Methods:
A cross-sectional survey was carried out in M. S. Ramaiah Medical and Dental Hospitals among 300 auxiliary health workers which comprised of laboratory technicians, hygienists, laundry workers, and the housekeeping staff. After acquiring ethical clearance and informed written consent, they were explained about the objective of the study and were requested to fill a standard questionnaire. The data was compiled and subjected to statistical analysis using the Statistical Package for Social Sciences (SPSS) software.
Statistical Analysis Used:
SPSS Software Version 19.
Results:
Our survey revealed that 90.03% of the respondents were aware of hepatitis B infection (HBI) and 67.2% answered questions correctly on risk perception. Only 37% of the respondents correctly answered questions on biomedical waste management.
Conclusions:
Overall, an adequate awareness and a moderate occupational risk perception about HBI were found among the study group. However, knowledge regarding hospital waste disposal was found to be insufficient. Our vision aims at a nation committed to combat silent epidemic of viral hepatitis infection.
doi:10.4103/2231-0762.122434
PMCID: PMC4000914  PMID: 24778982
Auxiliary healthcare workers; biomedical waste management; blood borne diseases; hepatitis B infection; infection control; needle stick injury; occupational exposure
23.  Impact of Community-Based Maternal Health Workers on Coverage of Essential Maternal Health Interventions among Internally Displaced Communities in Eastern Burma: The MOM Project 
PLoS Medicine  2010;7(8):e1000317.
Mullany and colleagues report outcomes from a project involving delivery of community-based maternal health services in eastern Burma, and report substantial increases in coverage of care.
Background
Access to essential maternal and reproductive health care is poor throughout Burma, but is particularly lacking among internally displaced communities in the eastern border regions. In such settings, innovative strategies for accessing vulnerable populations and delivering basic public health interventions are urgently needed.
Methods
Four ethnic health organizations from the Shan, Mon, Karen, and Karenni regions collaborated on a pilot project between 2005 and 2008 to examine the feasibility of an innovative three-tiered network of community-based providers for delivery of maternal health interventions in the complex emergency setting of eastern Burma. Two-stage cluster-sampling surveys among ever-married women of reproductive age (15–45 y) conducted before and after program implementation enabled evaluation of changes in coverage of essential antenatal care interventions, attendance at birth by those trained to manage complications, postnatal care, and family planning services.
Results
Among 2,889 and 2,442 women of reproductive age in 2006 and 2008, respectively, population characteristics (age, marital status, ethnic distribution, literacy) were similar. Compared to baseline, women whose most recent pregnancy occurred during the implementation period were substantially more likely to receive antenatal care (71.8% versus 39.3%, prevalence rate ratio [PRR] = 1.83 [95% confidence interval (CI) 1.64–2.04]) and specific interventions such as urine testing (42.4% versus 15.7%, PRR = 2.69 [95% CI 2.69–3.54]), malaria screening (55.9% versus 21.9%, PRR = 2.88 [95% CI 2.15–3.85]), and deworming (58.2% versus 4.1%, PRR = 14.18 [95% CI 10.76–18.71]. Postnatal care visits within 7 d doubled. Use of modern methods to avoid pregnancy increased from 23.9% to 45.0% (PRR = 1.88 [95% CI 1.63–2.17]), and unmet need for contraception was reduced from 61.7% to 40.5%, a relative reduction of 35% (95% CI 28%–40%). Attendance at birth by those trained to deliver elements of emergency obstetric care increased almost 10-fold, from 5.1% to 48.7% (PRR = 9.55 [95% CI 7.21–12.64]).
Conclusions
Coverage of maternal health interventions and higher-level care at birth was substantially higher during the project period. The MOM Project's focus on task-shifting, capacity building, and empowerment at the community level might serve as a model approach for similarly constrained settings.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Every minute, somewhere in the world, a woman dies of complications related to pregnancy and childbirth. Access to essential maternal and reproductive health care (including family planning) is particularly bad in war-torn countries. In Burma, for example, where there have been decades of conflict between the military junta and ethnic minority resistance groups, the maternal mortality rate (the number of deaths among women from pregnancy-related causes per 100,000 live births) is around 380, whereas in neighboring Thailand it is only 44. Maternal health is even worse in the Shan, Mon, Karen, and Karenni regions of eastern Burma where ethnic conflicts and enforced village relocations have internally displaced more than half a million people. Here, the maternal mortality rate is around 1,200. In an effort to improve access to maternal health services in these regions, community-based organizations in Burma, the Johns Hopkins Center for Public Health and Human Rights, and the Global Health Access Program undertook an innovative pilot project—the Mobile Obstetric Medics (MOM) project—between 2005 and 2008. Local health workers from 12 communities in eastern Burma received training in antenatal care, obstetrics (the care of women during childbirth), postnatal care, and family planning at the Mae Tao Clinic in Mae Sot, Thailand. These “maternal health workers” then returned to Burma where they trained local health workers and traditional birth attendants to provide maternal health care to their communities.
Why Was This Study Done?
Before the MOM project started, nearly 3,000 women living in the study communities were surveyed to evaluate the coverage of essential antenatal care interventions such as urine testing for infections during pregnancy, screening for malaria, and deworming; Urinary tract infections, malaria, and hookworm infections all increase the risk of poor maternal and neonatal outcomes. The preproject survey also evaluated how many births were attended by people able to deal with complications, and the provision of postnatal care and family planning services. In this study, the researchers undertake a similar postproject survey to evaluate the impact of MOM on the coverage of essential maternal health interventions among internally displaced communities in eastern Burma.
What Did the Researchers Do and Find?
Between October 2008 and December 2008, trained survey workers asked nearly 2,500 ever-married women of reproductive age from the project's study communities about their access to antenatal and postnatal care, skilled birth attendants, and family planning. The results of the postproject survey were then compared with those of the “baseline,” preproject survey. The general characteristics (age, marital status, ethnicity, and literacy) of the women included in the two surveys were very similar. However, 71.8% of the women whose most recent pregnancy occurred during the implementation period of the MOM project had received antenatal care compared to only 39.3% of women surveyed at baseline. Similarly, among the women questioned during the postproject survey, 42.4% had had their urine tested and 55.9% had been screened for malaria during pregnancy compared to only 15.7% and 21.9%, respectively, of the women questioned in the preproject survey. Deworming had increased from 4.1% to 58.2% during the project, postnatal care visits within 7 days had doubled, and attendance at birth by people trained to deal with obstetric emergencies had increased 10-fold from 5.1% to 48.7%. Finally, the use of modern contraception methods (slow-release contraceptives, oral contraceptives, and condoms) had increased from 23.9% to 45.0%.
What Do These Findings Mean?
These findings reveal a substantial improvement in access to maternal and reproductive health care in the study communities during the MOM project. However, because the study compared two independent groups of women before and after implementation of the MOM project rather than concurrently comparing groups of women who did and did not receive the services provided by the MOM project, this study does not prove that the MOM approach was the cause of the changes in the coverage of essential maternal health care. Nevertheless, these findings suggest that the type of approach used in the MOM project—the expansion of interventions (including components of emergency obstetric care) delivered outside healthcare facilities by community-based providers—might be an effective way to deliver maternal and reproductive health services in other parts of Burma and in other places where there are ongoing conflicts.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000317.
More information about the MOM project is available in previous publications by the researchers in PLoS Medicine, in Reproductive Health Matters, and in Social Science and Medicine
Additional resources are also available on the MOM Project
The Reproductive Health Response in Conflict Consortium provides information on how conflicts affect reproductive health
The World Health Organization provides information on all aspects of health in Burma (in several languages)
The Mae Tao clinic also provides general information about Burma and its health services
The Burma Campaign UK and Human Rights Watch both provide detailed information about human rights violations, including those that affect maternal health in Burma
The United Nations Population Fund provides information about safe motherhood and maternal and reproductive health during conflicts and among refugees (in several languages)
doi:10.1371/journal.pmed.1000317
PMCID: PMC2914639  PMID: 20689805
24.  Urbanicity and Lifestyle Risk Factors for Cardiometabolic Diseases in Rural Uganda: A Cross-Sectional Study 
PLoS Medicine  2014;11(7):e1001683.
Johanna Riha and colleagues evaluate the association of lifestyle risk factors with elements of urbanicity, such as having a public telephone, a primary school, or a hospital, among individuals living in rural settings in Uganda.
Please see later in the article for the Editors' Summary
Background
Urban living is associated with unhealthy lifestyles that can increase the risk of cardiometabolic diseases. In sub-Saharan Africa (SSA), where the majority of people live in rural areas, it is still unclear if there is a corresponding increase in unhealthy lifestyles as rural areas adopt urban characteristics. This study examines the distribution of urban characteristics across rural communities in Uganda and their associations with lifestyle risk factors for chronic diseases.
Methods and Findings
Using data collected in 2011, we examined cross-sectional associations between urbanicity and lifestyle risk factors in rural communities in Uganda, with 7,340 participants aged 13 y and above across 25 villages. Urbanicity was defined according to a multi-component scale, and Poisson regression models were used to examine associations between urbanicity and lifestyle risk factors by quartile of urbanicity. Despite all of the villages not having paved roads and running water, there was marked variation in levels of urbanicity across the villages, largely attributable to differences in economic activity, civil infrastructure, and availability of educational and healthcare services. In regression models, after adjustment for clustering and potential confounders including socioeconomic status, increasing urbanicity was associated with an increase in lifestyle risk factors such as physical inactivity (risk ratio [RR]: 1.19; 95% CI: 1.14, 1.24), low fruit and vegetable consumption (RR: 1.17; 95% CI: 1.10, 1.23), and high body mass index (RR: 1.48; 95% CI: 1.24, 1.77).
Conclusions
This study indicates that even across rural communities in SSA, increasing urbanicity is associated with a higher prevalence of lifestyle risk factors for cardiometabolic diseases. This finding highlights the need to consider the health impact of urbanization in rural areas across SSA.
Please see later in the article for the Editors' Summary
Editors’ Summary
Background
Cardiometabolic diseases—cardiovascular diseases that affect the heart and/or the blood vessels and metabolic diseases that affect the cellular chemical reactions needed to sustain life—are a growing global health concern. In sub-Saharan Africa, for example, the prevalence (the proportion of a population that has a given disease) of adults with diabetes (a life-shortening metabolic disease that affects how the body handles sugars) is currently 3.8%. By 2030, it is estimated that the prevalence of diabetes among adults in this region will have risen to 4.6%. Similarly, in 2004, around 1.2 million deaths in sub-Saharan Africa were attributed to coronary heart disease, heart failure, stroke, and other cardiovascular diseases. By 2030, the number of deaths in this region attributable to cardiovascular disease is expected to double. Globally, cardiovascular disease and diabetes are now responsible for around 17.3 million and 1.3 million annual deaths, respectively, together accounting for about one-third of all deaths.
Why Was This Study Done?
Experts believe that increased consumption of saturated fats, sugar, and salt and reduced physical activity are partly responsible for the increasing global prevalence of cardiometabolic diseases. These lifestyle changes, they suggest, are related to urbanization—urban expansion into the countryside and migration from rural to urban areas. If this is true, the prevalence of unhealthy lifestyles should increase as rural areas adopt urban characteristics. Sub-Saharan Africa is the least urbanized region in the world, with about 60% of the population living in rural areas. However, rural settlements across the subcontinent are increasingly adopting urban characteristics. It is important to know whether urbanization is affecting the health of rural residents in sub-Saharan Africa to improve estimates of the future burden of cardiometabolic diseases in the region and to provide insights into ways to limit this burden. In this cross-sectional study (an investigation that studies participants at a single time point), the researchers examine the distribution of urban characteristics across rural communities in Uganda and the association of these characteristics with lifestyle risk factors for cardiometabolic diseases.
What Did the Researchers Do and Find?
For their study, the researchers used data collected in 2011 by the General Population Cohort study, a study initiated in 1989 to describe HIV infection trends among people living in 25 villages in rural southwestern Uganda that collects health-related and other information annually from its participants. The researchers quantified the “urbanicity” of the 25 villages using a multi-component scale that included information such as village size and economic activity. They then used statistical models to examine associations between urbanicity and lifestyle risk factors such as body mass index (BMI, a measure of obesity) and self-reported fruit and vegetable consumption for more than 7,000 study participants living in those villages. None of the villages had paved roads or running water. However, urbanicity varied markedly across the villages, largely because of differences in economic activity, civil infrastructure, and the availability of educational and healthcare services. Notably, increasing urbanicity was associated with an increase in lifestyle risk factors for cardiovascular diseases. So, for example, people living in villages with the highest urbanicity scores were nearly 20% more likely to be physically inactive and to eat less fruits and vegetables and nearly 50% more likely to have a high BMI than people living in villages with the lowest urbanicity scores.
What Do These Findings Mean?
These findings indicate that, across rural communities in Uganda, even a small increase in urbanicity is associated with a higher prevalence of potentially modifiable lifestyle risk factors for cardiometabolic diseases. These findings suggest, therefore, that simply classifying settlements as either rural or urban may not be adequate to capture the information needed to target strategies for cardiometabolic disease management and control in rural areas as they become more urbanized. Because this study was cross-sectional, it is not possible to say how long a rural population needs to experience a more urban environment before its risk of cardiometabolic diseases increases. Longitudinal studies are needed to obtain this information. Moreover, studies of other countries in sub-Saharan Africa are needed to show that these findings are generalizable across the region. However, based on these findings, and given that more than 553 million people live in rural areas across sub-Saharan Africa, it seems likely that increasing urbanization will have a substantial impact on the future health of populations throughout sub-Saharan Africa.
Additional Information
Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001683.
This study is further discussed in a PLOS Medicine Perspective by Fahad Razak and Lisa Berkman
The American Heart Association provides information on all aspects of cardiovascular disease and diabetes; its website includes personal stories about heart attacks, stroke, and diabetes
The US Centers for Disease Control and Prevention has information on heart disease, stroke, and diabetes (in English and Spanish)
The UK National Health Service Choices website provides information about cardiovascular disease and diabetes (including some personal stories)
The World Health Organization’s Global Noncommunicable Disease Network (NCDnet) aims to help low- and middle-income countries reduce illness and death caused by cardiometabolic and other non-communicable diseases
The World Heart Federation has recently produced a report entitled “Urbanization and Cardiovascular Disease”
Wikipedia has a page on urbanization (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
doi:10.1371/journal.pmed.1001683
PMCID: PMC4114555  PMID: 25072243
25.  A Comparative Analysis of Influenza Vaccination Programs 
PLoS Medicine  2006;3(10):e387.
Background
The threat of avian influenza and the 2004–2005 influenza vaccine supply shortage in the United States have sparked a debate about optimal vaccination strategies to reduce the burden of morbidity and mortality caused by the influenza virus.
Methods and Findings
We present a comparative analysis of two classes of suggested vaccination strategies: mortality-based strategies that target high-risk populations and morbidity-based strategies that target high-prevalence populations. Applying the methods of contact network epidemiology to a model of disease transmission in a large urban population, we assume that vaccine supplies are limited and then evaluate the efficacy of these strategies across a wide range of viral transmission rates and for two different age-specific mortality distributions.
We find that the optimal strategy depends critically on the viral transmission level (reproductive rate) of the virus: morbidity-based strategies outperform mortality-based strategies for moderately transmissible strains, while the reverse is true for highly transmissible strains. These results hold for a range of mortality rates reported for prior influenza epidemics and pandemics. Furthermore, we show that vaccination delays and multiple introductions of disease into the community have a more detrimental impact on morbidity-based strategies than mortality-based strategies.
Conclusions
If public health officials have reasonable estimates of the viral transmission rate and the frequency of new introductions into the community prior to an outbreak, then these methods can guide the design of optimal vaccination priorities. When such information is unreliable or not available, as is often the case, this study recommends mortality-based vaccination priorities.
A comparative analysis of two classes of suggested vaccination strategies, mortality-based strategies that target high-risk populations and morbidity-based strategies that target high-prevalence populations.
Editors' Summary
Background.
Influenza—a viral infection of the nose, throat, and airways that is transmitted in airborne droplets released by coughing or sneezing—is a serious public health threat. Most people recover quickly from influenza, but some individuals, especially infants, old people, and individuals with chronic health problems, can develop pneumonia and die. In the US, seasonal outbreaks (epidemics) of flu cause an estimated 36,000 excess deaths annually. And now there are fears that avian influenza might start a human pandemic—a global epidemic that could kill millions. Seasonal outbreaks of influenza occur because flu viruses continually change the viral proteins (antigens) to which the immune system responds. “Antigenic drift”—small changes in these proteins—means that an immune system response that combats flu one year may not provide complete protection the next winter. “Antigenic shift”—large antigen changes—can cause pandemics because communities have no immunity to the changed virus. Annual vaccination with vaccines based on the currently circulating viruses controls seasonal flu epidemics; to control a pandemic, vaccines based on the antigenically altered virus would have to be quickly developed.
Why Was This Study Done?
Most countries target vaccination efforts towards the people most at risk of dying from influenza, and to health-care workers who are likely come into contact with flu patients. But is this the best way to reduce the burden of illness (morbidity) and death (mortality) caused by influenza, particularly at the start of a pandemic, when vaccine would be limited? Old people and infants are much less likely to catch and spread influenza than school children, students, and employed adults, so could vaccination of these sections of the population—instead of those most at risk of death—be the best way to contain influenza outbreaks? In this study, the researchers used an analytical method called “contact network epidemiology” to compare two types of vaccination strategies: the currently favored mortality-based strategy, which targets high-risk individuals, and a morbidity-based strategy, which targets those segments of the community in which most influenza cases occur.
What Did the Researchers Do and Find?
Most models of disease transmission assume that each member of a community is equally likely to infect every other member. But a baby is unlikely to transmit flu to, for example, an unrelated, housebound elderly person. Contact network epidemiology takes the likely relationships between people into account when modeling disease transmission. Using information from Vancouver, British Columbia, Canada, on household size, age distribution, and occupations, and other factors such as school sizes, the researchers built a model population of a quarter of a million interconnected people. They then investigated how different vaccination strategies controlled the spread of influenza in this population. The optimal strategy depended on the level of viral transmissibility—the likelihood that an infectious person transmits influenza to a susceptible individual with whom he or she has contact. For moderately transmissible flu viruses, a morbidity-based vaccination strategy, in which the people most likely to catch the flu are vaccinated, was more effective at containing seasonal and pandemic outbreaks than a mortality-based strategy, in which the people most likely to die if they caught the flu are vaccinated. For highly transmissible strains, this situation was reversed. The level of transmissibility at which this reversal occurred depended on several factors, including whether vaccination was delayed and how many times influenza was introduced into the community.
What Do These Findings Mean?
The researchers tested their models by checking that they could replicate real influenza epidemics and pandemics, but, as with all mathematical models, they included many assumptions about influenza in their calculations, which may affect their results. Also, because the contact network used data from Vancouver, their results might not be applicable to other cities, or to nonurban areas. Nevertheless, their findings have important public health implications. When there are reasonable estimates of the viral transmission rate, and it is known how often influenza is being introduced into a community, contact network models could help public health officials choose between morbidity- and mortality-based vaccination strategies. When the viral transmission rate is unreliable or unavailable (for example, at the start of a pandemic), the best policy would be the currently preferred strategy of mortality-based vaccination. More generally, the use of contact network models should improve estimates of how infectious diseases spread through populations and indicate the best ways to control human epidemics and pandemics.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0030387.
US Centers for Disease Control and Prevention information about influenza for patients and professionals, including key facts on vaccination
US National Institute of Allergy and Infectious Diseases feature on seasonal, avian, and pandemic influenza
World Health Organization fact sheet on influenza, with links to information on vaccination
UK Health Protection Agency information on seasonal, avian, and pandemic influenza
MedlinePlus entry on influenza
doi:10.1371/journal.pmed.0030387
PMCID: PMC1584413  PMID: 17020406

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