Capture-recapture for estimating the size of the female sex worker population in three cities in Côte d'Ivoire and in Kisumu, western Kenya

Spatial Analysis of the Alcohol, Intimate Partner Violence, and HIV Syndemic Among Women in South Africa

The co-occurrence of and synergistic interactions between substance abuse, violence, and HIV, known as the "SAVA syndemic," is thought to be a driver of women's elevated risk for HIV in sub-Saharan Africa. This study uses data from the 2016 South African Demographic and Health Survey (DHS) and the 2016 South African Census to examine geospatial associations between alcohol use, intimate partner violence (IPV), unprotected sex, and HIV status among a population-based sample of 8528 South African women (age 15-49). Results support the geographic clustering of alcohol use, unprotected sex, and IPV, but not HIV, and geospatial clustering of HIV alone. This study highlights the need for geographically-tailored interventions to address syndemics through integrated interventions, such as those simultaneously focused on alcohol, IPV, and sexual risk reduction, and points to the need for more targeted research to link these factors to HIV from a place-based risk perspective.

Intentional abortion and its associated factors among female sex workers in Iran: Results from national bio-behavioral surveillance-2020

Purpose

In addition to estimating the prevalence of intentional abortion in Iranian female sex workers (FSWs), this study identified related factors using the data of a national study.

Methods

This cross-sectional study utilizes the third round of integrated bio-behavioral surveillance-III data in Iranian FSWs in December 2019 and August 2020, and 1515 Participants were selected in 8 geographically diverse cities in Iran. Logistic regression was performed using unweighted analysis to identify factors associated with intentional abortion. Stata software (version 14), respondent-driven sampling analyses, and R (version 4.1.2) was used for data analysis.

Results

From 1390 participants with valid responses to the abortion question, 598 (37.3%; 95% CI: 32.43, 42.11%) reported intentional abortion during their life. According to the age groups, the highest prevalence of abortion was in the age group of 31 to 40 years (42.60%). In the multivariate logistic regression model, the marital status (divorced women (AOR = 2.05, 95% CI: 1.29, 3.27), concubines (AOR = 1.78, 95% CI: 1.02, 3.11)), work experience in brothels (AOR = 1.39, 95% CI: 1.04, 1.84), the type of sex (AOR = 2.75, 95% CI: 1.35, 5.58), the history of sexual violence (AOR = 1.54, 95% CI: 1.19, 2.01), and alcohol consumption (AOR = 1.53, 95% CI: 1.18, 2.01) were significantly associated with a history of intentional abortion.

Conclusion

Intentional abortion’s prevalence among Iranian FSWs has been much higher than that of the general female population in Iran, which is an alarming issue in the public health of this group and needs more effective interventions. In addition, alcohol consumption, working in a brothel, and being divorced are essential factors in increasing abortions among sex workers.

Comparative performance of multiple-list estimators of key population size

Estimates of the sizes of key populations (KPs) affected by HIV, including men who have sex with men, female sex workers and people who inject drugs, are required for targeting epidemic control efforts where they are most needed. Unfortunately, different estimators often produce discrepant results, and an objective basis for choice is lacking. This simulation study provides the first comparison of information-theoretic selection of loglinear models (LLM-AIC), Bayesian model averaging of loglinear models (LLM-BMA) and Bayesian nonparametric latent-class modeling (BLCM) for estimation of population size from multiple lists. Four hundred random samples from populations of size 1,000, 10,000 and 20,000, each including five encounter opportunities, were independently simulated using each of 30 data-generating models obtained from combinations of six patterns of variation in encounter probabilities and five expected per-list encounter probabilities, producing a total of 36,000 samples. Population size was estimated for each combination of sample and sequentially cumulative sets of 2-5 lists using LLM-AIC, LLM-BMA and BLCM. LLM-BMA and BLCM were quite robust and performed comparably in terms of root mean-squared error and bias, and outperformed LLM-AIC. All estimation methods produced uncertainty intervals which failed to achieve the nominal coverage, but LLM-BMA, as implemented in the dga R package produced the best balance of accuracy and interval coverage. The results also indicate that two-list estimation is unnecessarily vulnerable, and it is better to estimate the sizes of KPs based on at least three lists.

Factors Associated with Likelihood of Initiating Others into Injection Drug Use Among People Who Inject Drugs in West Virginia

People who inject drugs (PWID) play a critical role in injection-naïve individuals transitioning to injection drug use. We investigated factors associated with future likelihood of initiating injection-naïve individuals using multivariable logistic regression among 418 PWID in rural Appalachia (Cabell County, West Virginia). Less than 10% reported they were likely to initiate someone in the future. Acquiring syringes from a syringe services program was associated with decreased odds of being likely to initiate someone in the future (adjusted odds ratio [aOR] 0.46, 95% CI 0.23, 0.95), while having previously initiated someone into injection drug use was associated with increased odds (aOR 8.65, 95% CI 4.07, 18.41). Among our sample of PWID in Appalachia, a small proportion reported that they would be likely to initiate an injection-naïve individual in the future. Efforts to reduce injection initiation assistance should focus on this subpopulation of PWID who indicate a willingness to engage in this behavior.

shinyrecap: A Shiny Application for Population Size Estimation from Capture-Recapture Data (Preprint)

Background

Population size estimates (PSE) provide critical information in determining resource allocation for HIV services geared toward those at high risk of HIV, including female sex workers, men who have sex with men, and people who inject drugs. Capture-recapture (CRC) is often used to estimate the size of these often-hidden populations. Compared with the commonly used 2-source CRC, CRC relying on 3 (or more) samples (3S-CRC) can provide more robust PSE but involve far more complex statistical analysis.

Objective

This study aims to design and describe the Shiny application (shinyrecap), a user-friendly interface that can be used by field epidemiologists to produce PSE.

Methods

shinyrecap is built on the Shiny web application framework for R. This allows it to seamlessly integrate with the sophisticated CRC statistical packages (eg, Rcapture, dga, LCMCR). Additionally, the application may be accessed online or run locally on the user’s machine.

Results

The application enables users to engage in sample size calculation based on a simulation framework. It assists in the proper formatting of collected data by providing a tool to convert commonly used formats to that used by the analysis software. A wide variety of methodologies are supported by the analysis tool, including log-linear, Bayesian model averaging, and Bayesian latent class models. For each methodology, diagnostics and model checking interfaces are provided.

Conclusions

Through a use case, we demonstrated the broad utility of this powerful tool with 3S-CRC data to produce PSE for female sex workers in a subnational unit of a country in sub-Saharan Africa.

Population Size Estimation of Female Sex Workers in Hai Phong, Vietnam: Use of Three Source Capture-Recapture Method

Introduction: A study was conducted in three districts in Hai Phong province, Vietnam to estimate the population size of the Female Sex Workers (FSW) in June–July 2019.

Methods: The procedures included selection of three districts, compilation of a list of accessible venues where FSW congregate, distribution of first unique objects (first capture) and second unique objects (second capture) to FSW in randomly selected venues and implementation of a Mini-Respondent Driven Sampling (mRDS) Survey (third capture). Population size of the FSW was calculated based on the number of FSW in each round, number of FSW ‘recaptured’ during the second and the third captures. Additionally, personal network size data captured in the mRDS was used to measure the population of FSW within the three districts using Successive Sampling Population Size Estimates (SS-PSE).

Results: The total estimated FSWs in the three selected districts, using Three Source Capture–Recapture (3S-CRC) was 958, which is slightly lower than that estimated using SS-PSE – 1192. The 3S-CRC method yielded a provincial estimate of 1911 while the SS-PSE method resulted in a total of 2379 FSW for the province.

Conclusion: Two techniques produced different PSE at both the district and the province levels and resulted in estimates lower than ones produced using programmatic data. For planning HIV prevention and care service needs among all FSWs, additional studies are needed to estimate the number of sex workers who are not venue-based and use social media platforms to sell services.

Female sex workers population size estimation in Rwanda using a three-source capture-recapture method

Establishing accurate population size estimates (PSE) is important for prioritising and planning provision of services. Multiple source capture−recapture sampling method increases PSE accuracy and reliability. In August 2018, the three-source capture−recapture (3S-CRC) method was employed with a stringent assumption of sample independence to estimate the number of female sex workers (FSW) in Rwanda. Using Rwanda 2017 FSW hotspots mapping data, street and venue-based FSW were sampled at the sector level of each province and tagged with two unique gifts. Each capture was completed within one week to minimise FSW migration between provinces and recall bias. The three captures had 1042, 1204 and 1488 FSW. There were 111 FSW recaptured between captures 1 and 2; 237 between captures 2 and 3; 203 between captures 1 and 3 and 46 captured in all three. The PSE for street and venue-based FSW in Rwanda lies within 95% credible set: 8328–22 806 with corresponding median of 13 716 FSW. The 3S-CRC technique was low-cost and relatively easy to use for PSE in hard-to-reach populations. This estimate provides the basis for determining the denominators to assess HIV programme performance towards FSW and epidemic control and warrants further PSE for home- and cyber-based FSW in Rwanda.

Correlates of recent nonfatal overdose among people who inject drugs in West Virginia

Aim

Experiencing a nonfatal overdose (NFOD) is a significant risk factor for a subsequent nonfatal or fatal overdose. Overdose mortality rates in rural Appalachian states are some of the highest in the USA, but little is known about correlates of overdose among rural populations of people who inject drugs (PWID). Our study aimed to identify correlates of experiencing a recent (past 6 months) NFOD among rural PWID in Cabell County, West Virginia.

Methods

Using data from a June–July 2018 cross-sectional survey that was designed to estimate the size and characteristics of the PWID population in Cabell County, West Virginia, we used log binomial regression to identify correlates (e.g., structural vulnerabilities and substance use) of NFOD in the past 6 months.

Results

The majority of our sample of 420 PWID were male (61.2%), White, non-Hispanic (83.6%), and reported recent heroin injection (81.0%). More than two-fifths (42.6%) experienced a recent NFOD. Independent correlates of NFOD included witnessing an overdose in the past 6 months (adjusted prevalence ratio [aPR] = 2.28; 95% CI 1.48–3.50), attempting to quit using drugs in the past 6 months (aPR = 1.54; 95% CI 1.11–2.14), and the number of drugs injected (aPR = 1.16; 95% CI 1.10–1.23)

Conclusions

A large proportion of rural PWID in Appalachia reported having recently overdosed. The associations between witnessing an overdose, attempting to quit using drugs, and number of drugs injected with recent nonfatal overdose underscore the need for expanded access to overdose prevention resources that are tailored to the needs of this population. Expanding access to evidence-based overdose prevention strategies—such as take-home naloxone programs, treatment with methadone or buprenorphine, and harm reduction services—may decrease overdose morbidity and mortality among rural PWID in Appalachia.

Assessing Bias in Population Size Estimates Among Hidden Populations When Using the Service Multiplier Method Combined With Respondent-Driven Sampling Surveys: Survey Study

BACKGROUND

Population size estimates (PSEs) for hidden populations at increased risk of HIV, including female sex workers (FSWs), are important to inform public health policy and resource allocation. The service multiplier method (SMM) is commonly used to estimate the sizes of hidden populations. We used this method to obtain PSEs for FSWs at 9 sites in Zimbabwe and explored methods for assessing potential biases that could arise in using this approach.

OBJECTIVE

This study aimed to guide the assessment of biases that arise when estimating the population sizes of hidden populations using the SMM combined with respondent-driven sampling (RDS) surveys.

METHODS

We conducted RDS surveys at 9 sites in late 2013, where the Sisters with a Voice program (the program), which collects program visit data of FSWs, was also present. Using the SMM, we obtained PSEs for FSWs at each site by dividing the number of FSWs who attended the program, based on program records, by the RDS-II weighted proportion of FSWs who reported attending this program in the previous 6 months in the RDS surveys. Both the RDS weighting and SMM make a number of assumptions, potentially leading to biases if the assumptions are not met. To test these assumptions, we used convergence and bottleneck plots to assess seed dependence of RDS-II proportion estimates, chi-square tests to assess if there was an association between the characteristics of FSWs and their knowledge of program existence, and logistic regression to compare the characteristics of FSWs attending the program with those recruited to RDS surveys.

RESULTS

The PSEs ranged from 194 (95% CI 62-325) to 805 (95% CI 456-1142) across 9 sites from May to November 2013. The 95% CIs for the majority of sites were wide. In some sites, the RDS-II proportion of women who reported program use in the RDS surveys may have been influenced by the characteristics of selected seeds, and we also observed bottlenecks in some sites. There was no evidence of association between characteristics of FSWs and knowledge of program existence, and in the majority of sites, there was no evidence that the characteristics of the populations differed between RDS and program data.

CONCLUSIONS

We used a series of rigorous methods to explore potential biases in our PSEs. We were able to identify the biases and their potential direction, but we could not determine the ultimate direction of these biases in our PSEs. We have evidence that the PSEs in most sites may be biased and a suggestion that the bias is toward underestimation, and this should be considered if the PSEs are to be used. These tests for bias should be included when undertaking population size estimation using the SMM combined with RDS surveys.

The uptake of population size estimation studies for key populations in guiding HIV responses on the African continent

Background

There has been a heightened emphasis on prioritizing data to inform evidence-based HIV responses, including data focused on both defining the content and scale of HIV programs in response to evidence-based need. Consequently, population size estimation (PSE) studies for key populations have become increasingly common to define the necessary scale of specific programs for key populations. This study aims to assess the research utilization of these size estimates in informing HIV policy and program documents across the African continent.

Methods

This study included two phases; Phase 1 was a review of all PSE for key populations, including men who have sex with men (MSM), female sex workers (FSW), people who use drugs (PWUD), and transgender persons in the 54 countries across Africa published from January 2009—December 2017. Phase 2 was a review of 23 different types of documents released between January 2009 –January 2019, with a focus on the US President’s Emergency Plan for AIDS Relief (PEPFAR) and The Global Fund to Fight AIDS, Tuberculosis and Malaria investments, for evidence of stakeholder engagement in PSE studies, as well as key population PSE research utilization to inform HIV programming and international HIV investments.

Results

Of 118 size estimates identified in 39 studies, less than 15% were utilized in PEPFAR Country Operational Plans or national strategic health plan documents, and less than 2% in Global Fund Concept Notes. Of 39 PSE studies, over 50% engaged stakeholders in study implementation and identified target population stakeholders, a third of studies identified policy or program stakeholders, and 15% involved stakeholders in study design.

Conclusion

The past decade has seen an increase in PSE studies conducted for key populations in more generalized HIV epidemic settings which involve significant investments of finances and human resources. However, there remains limited evidence of sustained uptake of these data to guide the HIV responses. Increasing uptake necessitates effective stakeholder engagement and data-oriented capacity building to optimize research utilization and facilitate data-driven and human rights-affirming HIV responses.

¿Te Recurseas? Mapping, Enumerating, and Describing Male and Transwomen Sex Workers in Venue-Based and Virtual Spaces in Lima, Peru

HIV disproportionately affects men who have sex with men and transwomen in Latin America. Globally, efforts to map, enumerate, and describe male and transwomen sex workers (MTSWs) are limited. We mapped and described venue- and non-venue-based MTSWs and enumerated venuebased MTSWs in Lima, Peru's capital. With venue-based MTSWs, we identified and described the venues, SWs, and clients and enumerated the SWs. With non-venue-based MTSWs, we described SW offerings and SWs. Male SWs (MSWs) are concentrated downtown, with many moving online. Transwomen SWs (TSWs) are spread across metropolitan Lima, with fewer online. At venues, there are more TSWs than MSWs, TSWs reported more HIV and sexual risk behaviors, and MSWs had more female partners. Non-venue-based MSWs used condoms less than venue-based MSWs. Results support systematic efforts to describe hard-to-reach MTSWs and their different types of partners, all of whom have unique, differing needs for HIV/ STI education, prevention, testing, and care services.

Geographic Information Systems, spatial analysis, and HIV in Africa: A scoping review

INTRODUCTION

Geographic Information Systems (GIS) and spatial analysis are emerging tools for global health, but it is unclear to what extent they have been applied to HIV research in Africa. To help inform researchers and program implementers, this scoping review documents the range and depth of published HIV-related GIS and spatial analysis research studies conducted in Africa.

METHODS

A systematic literature search for articles related to GIS and spatial analysis was conducted through PubMed, EMBASE, and Web of Science databases. Using pre-specified inclusion criteria, articles were screened and key data were abstracted. Grounded, inductive analysis was conducted to organize studies into meaningful thematic areas.

RESULTS AND DISCUSSION

The search returned 773 unique articles, of which 65 were included in the final review. 15 different countries were represented. Over half of the included studies were published after 2014. Articles were categorized into the following non-mutually exclusive themes: (a) HIV geography, (b) HIV risk factors, and (c) HIV service implementation. Studies demonstrated a broad range of GIS and spatial analysis applications including characterizing geographic distribution of HIV, evaluating risk factors for HIV, and assessing and improving access to HIV care services.

CONCLUSIONS

GIS and spatial analysis have been widely applied to HIV-related research in Africa. The current literature reveals a diversity of themes and methodologies and a relatively young, but rapidly growing, evidence base.

Novel Approaches for Estimating Female Sex Worker Population Size in Conflict-Affected South Sudan

Background

Limited data exist describing the population size of female sex workers (FSW) in South Sudan. A population size estimation exercise among FSW was undertaken in Juba and Nimule during the Eagle Survey.

Objective

The study aimed to estimate the number of FSW in Juba and Nimule to inform resource allocation and service provision for FSW.

Methods

We utilized service and unique object multipliers, and 3-source capture-recapture methods in conjunction with a respondent-driven sampling (RDS) survey to estimate the number of FSW in Juba and Nimule. For service multiplier, the number of FSW testing for HIV in 2015 (Juba) and 2016 (Nimule) was obtained from the LINKAGES program targeting FSW. Survey participants were asked whether they had been tested for HIV by LINKAGES during the relevant period. A total of 2 separate unique object distributions were conducted in Juba and Nimule. In Nimule, these were combined to produce a 3-source capture-recapture estimate. The exercise involved distribution of key chains and bangles to FSW, documentation of the number of those who received unique objects, and questions during RDS survey to assess whether participants received unique objects.

Results

In Juba, the service multiplier method yielded an estimate of 5800 (95% CI 4927-6673) FSW. The unique object estimate (key chain and RDS participation) yielded 5306 (95% CI 4673-5939). Another estimate using RDS participation and receipt of a bangle yielded a much lower estimate of 1863 (95% CI 1776-1951), as did a 2-source estimate of key chain and bangle (2120, 95% CI 2028-2211). A 3-source capture-recapture estimate could not be produced because aggregate rather than individual level data were collected during the third capture. The multiplier estimate using key chain and RDS participation was taken as the final population estimate for FSW in Juba, which constitutes more than 6% of the female population aged 15 to 64 years.

In Nimule, the service multiplier method yielded an estimate of 9384 (95% CI 8511-10,257). The 2-source estimates for key chain and RDS yielded 6973 (95% CI 4759-9186); bangles and RDS yielded a higher estimate of 13,104 (95% CI 7101-19,106); key chains and bangles yielded a lower estimate of 1322 (95% CI 1223-1420). The 3-source capture-recapture method using Bayesian nonparametric latent-class model-based estimate yielded a population of 2694 (95% CI 1689-6945), and this was selected as the final estimate for Nimule, which constitutes nearly 40% of female population aged 15 to 64 years.

Conclusions

The service and unique object multiplier, and 3-source capture-recapture methods were successfully used to estimate the number of FSW in Nimule, whereas service and unique object multiplier methods were successfully used in Juba. These methods yielded higher than previously estimated FSW population sizes. These estimates will inform resource allocation and advocacy efforts to support services for FSW.

Estimating the Number of People Who Inject Drugs in A Rural County in Appalachia

OBJECTIVES

To demonstrate how we applied the capture-recapture method for population estimation directly in a rural Appalachian county (Cabell County, WV) to estimate the number of people who inject drugs (PWID).

METHODS

We conducted 2 separate 2-week periods of data collection in June ("capture") and July ("recapture") 2018. We recruited PWID from a syringe services program and in community locations where PWID were known to congregate. Participants completed a survey that included measures related to sociodemographics, substance use, and HIV and hepatitis C virus prevention.

RESULTS

In total, 797 surveys were completed; of these surveys, 49.6% (n = 395) reflected PWID who reported injection drug use in the past 6 months and Cabell County residence. We estimated that there were 1857 (95% confidence interval = 1147, 2567) PWID in Cabell County. Among these individuals, most reported being White (83.4%), younger than 40 years (70.9%), and male (59.5%). The majority reported injecting heroin (82.0%), methamphetamine (71.0%), and fentanyl (56.3%) in the past 6 months.

CONCLUSIONS

Capture-recapture methods can be applied in rural settings to estimate the size of PWID populations.

One-step estimation of networked population size: Respondent-driven capture-recapture with anonymity

Size estimation is particularly important for populations whose members experience disproportionate health issues or pose elevated health risks to the ambient social structures in which they are embedded. Efforts to derive size estimates are often frustrated when the population is hidden or hard-to-reach in ways that preclude conventional survey strategies, as is the case when social stigma is associated with group membership or when group members are involved in illegal activities. This paper extends prior research on the problem of network population size estimation, building on established survey/sampling methodologies commonly used with hard-to-reach groups. Three novel one-step, network-based population size estimators are presented, for use in the context of uniform random sampling, respondent-driven sampling, and when networks exhibit significant clustering effects. We give provably sufficient conditions for the consistency of these estimators in large configuration networks. Simulation experiments across a wide range of synthetic network topologies validate the performance of the estimators, which also perform well on a real-world location-based social networking data set with significant clustering. Finally, the proposed schemes are extended to allow them to be used in settings where participant anonymity is required. Systematic experiments show favorable tradeoffs between anonymity guarantees and estimator performance. Taken together, we demonstrate that reasonable population size estimates are derived from anonymous respondent driven samples of 250-750 individuals, within ambient populations of 5,000-40,000. The method thus represents a novel and cost-effective means for health planners and those agencies concerned with health and disease surveillance to estimate the size of hidden populations. We discuss limitations and future work in the concluding section.

Estimating the Population Size of Female Sex Worker Population in Tehran, Iran: Application of Direct Capture-Recapture Method

There is no reliable estimate of the size of female sex workers (FSWs). This study aimed to estimate the size of FSWs in south of Tehran, Iran in 2016 using direct capture-recapture method. In the capture phase, the hangouts of FSWs were mapped as their meeting places. FSWs who agreed to participate in the study tagged with a T-shirt. The recapture phase was implemented at the same places tagging FSWs with a blue bracelet. The total estimated size of FSWs was 690 (95% CI 633, 747). About 89.43% of FSWs experienced sexual intercourse prior to age 20. The prevalence of human immunodeficiency virus infection among FSWs was 4.60%. The estimated population size of FSWs was much more than our expectation. This issue must be the focus of special attention for planning prevention strategies. However, alternative estimates require to estimating the number FSWs, reliably.

Estimating the number of female sex workers in Côte d'Ivoire: results and lessons learned

OBJECTIVE

To report on the results of three size estimations of the populations of female sex workers (FSW) in five cities in Côte d'Ivoire and on operational lessons learned, which may be relevant for key population programmes in other parts of the world.

METHODS

We applied three methods: mapping and census, capture-recapture and service multiplier. All were applied between 2008 and 2009 in Abidjan, San Pedro, Bouaké, Yamoussoukro and Abengourou.

RESULTS

Abidjan was the city with the highest number of FSW by far, with estimations between 7880 (census) and 13 714 (service multiplier). The estimations in San Pedro, Bouaké and Yamoussoukro were very similar, with figures ranging from 1160 (Yamoussoukro, census) to 1916 (San Pedro, capture-recapture). Important operational lessons were learned, including strategies for mapping, the importance of involving peer sex workers for implementing the capture-recapture and the identification of the right question for the multiplier method.

CONCLUSIONS

Successful application of three methods to estimate the population size of FSW in five cities in Côte d'Ivoire enabled us to make recommendations for size estimations of key population in low-income countries.

A comprehensive review of available epidemiologic and HIV service data for female sex workers, men who have sex with men, and people who inject drugs in select West and Central African countries

OBJECTIVE

To identify gaps in epidemiologic and HIV service coverage data for key populations (KP), including men who have sex with men (MSM), female sex workers (FSW), people who inject drugs (PWID), and transgender persons, in 8 West and Central Africa countries: Cameroon, Chad, Cote d'Ivoire, Democratic Republic of Congo, Ghana, Guinea-Bissau, Niger, and Nigeria.

METHODS

A comprehensive search of peer-reviewed literature was conducted using PubMed and MEDLINE. This search was supplemented by an additional search of relevant non-peer-reviewed, or gray, literature. Available data on HIV prevalence, KP size estimates, HIV prevention service targets, and HIV prevention service coverage, including the availability of population-specific minimum packages of services, were included in the review.

RESULTS

No data for transgender persons were found. HIV prevalence data and size estimates were more frequently available for FSW, followed by MSM. Only 2 countries (Ghana and Nigeria) had both KP size estimates and HIV prevalence data for PWID. The degree to which HIV prevention service targets were adopted was highly variable across the selected countries, and the collection of relevant HIV prevention service coverage data for those targets that were identified was inconsistent. Population-specific minimum packages of services were identified in 3 countries (Cote d'Ivoire, Ghana, and Nigeria), although only Ghana and Nigeria included services for PWID.

CONCLUSIONS

Epidemiologic and HIV prevention service data for FSW, MSM, PWID, and transgender persons remain sparse, and these KP are inconsistently accounted for in-service delivery and nationally endorsed minimum packages of HIV services in West and Central Africa. The strengthening of data collection and reporting to consistently include KP and the inclusion of that data in national planning is imperative for effectively addressing the HIV epidemic.

Estimating the number of sex workers in South Africa: rapid population size estimation

Although recognized as a vulnerable population, there is no national population size estimate for sex workers in South Africa. A rapid sex worker enumeration exercise was undertaken in twelve locations across the country based on principles of participatory mapping and Wisdom of the Crowd. Sites with a range of characteristics were selected, focusing on level of urbanisation, trucking, mining and borders. At each site, sex worker focus groups mapped local hotspots. Interviews with sex workers at identified hotspots were used to estimate the numbers and genders of sex workers working in each. Estimates provided in the literature were combined with enumeration exercise results to define assumptions that could be applied to a national extrapolation. A working estimate was reached of between 131,000 and 182,000 sex worker in South Africa, or between 0.76 and 1 % of the adult female population. The success of the exercise depended on integral involvement of sex worker peer educators and strong ethical considerations.

Social support and condom use among female sex workers in China

While the relationship between social support and psychological well-being has been well established, limited studies have explored how social support might affect condom use among female sex workers (FSWs). Using cross-sectional data from 1,022 FSWs in Guangxi, China, we examined how different forms of support from diverse sources may influence condom use among FSWs. Friends, coworkers, and stable partners were FSWs' main sources of social support. Social support from diverse sources differently impacts FSWs' condom use. Policymakers need to consider the complicated profile of social support received by FSWs and create supportive environment for FSWs to protect themselves from HIV risks.

Estimation of the size of the female sex worker population in Rwanda using three different methods

HIV prevalence is disproportionately high among female sex workers compared to the general population. Many African countries lack useful data on the size of female sex worker populations to inform national HIV programmes. A female sex worker size estimation exercise using three different venue-based methodologies was conducted among female sex workers in all provinces of Rwanda in August 2010. The female sex worker national population size was estimated using capture–recapture and enumeration methods, and the multiplier method was used to estimate the size of the female sex worker population in Kigali. A structured questionnaire was also used to supplement the data. The estimated number of female sex workers by the capture–recapture method was 3205 (95% confidence interval: 2998–3412). The female sex worker size was estimated at 3348 using the enumeration method. In Kigali, the female sex worker size was estimated at 2253 (95% confidence interval: 1916–2524) using the multiplier method. Nearly 80% of all female sex workers in Rwanda were found to be based in the capital, Kigali. This study provided a first-time estimate of the female sex worker population size in Rwanda using capture–recapture, enumeration, and multiplier methods. The capture–recapture and enumeration methods provided similar estimates of female sex worker in Rwanda. Combination of such size estimation methods is feasible and productive in low-resource settings and should be considered vital to inform national HIV programmes.

Validation of the modes of transmission model as a tool to prioritize HIV prevention targets: a comparative modelling analysis

Background

The static Modes of Transmission (MOT) model predicts the annual fraction of new HIV infections acquired across subgroups (MOT metric), and is used to focus HIV prevention. Using synthetic epidemics via a dynamical model, we assessed the validity of the MOT metric for identifying epidemic drivers (behaviours or subgroups that are sufficient and necessary for HIV to establish and persist), and the potential consequence of MOT-guided policies.

Methods and Findings

To generate benchmark MOT metrics for comparison, we simulated three synthetic epidemics (concentrated, mixed, and generalized) with different epidemic drivers using a dynamical model of heterosexual HIV transmission. MOT metrics from generic and complex MOT models were compared against the benchmark, and to the contribution of epidemic drivers to overall HIV transmission (cumulative population attributable fraction over t years, PAF_t). The complex MOT metric was similar to the benchmark, but the generic MOT underestimated the fraction of infections in epidemic drivers. The benchmark MOT metric identified epidemic drivers early in the epidemics. Over time, the MOT metric did not identify epidemic drivers. This was not due to simplified MOT models or biased parameters but occurred because the MOT metric (irrespective of the model used to generate it) underestimates the contribution of epidemic drivers to HIV transmission over time (PAF_5–30). MOT-directed policies that fail to reach epidemic drivers could undermine long-term impact on HIV incidence, and achieve a similar impact as random allocation of additional resources.

Conclusions

Irrespective of how it is obtained, the MOT metric is not a valid stand-alone tool to identify epidemic drivers, and has limited additional value in guiding the prioritization of HIV prevention targets. Policy-makers should use the MOT model judiciously, in combination with other approaches, to identify epidemic drivers.

Community empowerment and involvement of female sex workers in targeted sexual and reproductive health interventions in Africa: a systematic review

Background

Female sex workers (FSWs) experience high levels of sexual and reproductive health (SRH) morbidity, violence and discrimination. Successful SRH interventions for FSWs in India and elsewhere have long prioritised community mobilisation and structural interventions, yet little is known about similar approaches in African settings. We systematically reviewed community empowerment processes within FSW SRH projects in Africa, and assessed them using a framework developed by Ashodaya, an Indian sex worker organisation.

Methods

In November 2012 we searched Medline and Web of Science for studies of FSW health services in Africa, and consulted experts and websites of international organisations. Titles and abstracts were screened to identify studies describing relevant services, using a broad definition of empowerment. Data were extracted on service-delivery models and degree of FSW involvement, and analysed with reference to a four-stage framework developed by Ashodaya. This conceptualises community empowerment as progressing from (1) initial engagement with the sex worker community, to (2) community involvement in targeted activities, to (3) ownership, and finally, (4) sustainability of action beyond the community.

Results

Of 5413 articles screened, 129 were included, describing 42 projects. Targeted services in FSW ‘hotspots’ were generally isolated and limited in coverage and scope, mostly offering only free condoms and STI treatment. Many services were provided as part of research activities and offered via a clinic with associated community outreach. Empowerment processes were usually limited to peer-education (stage 2 of framework). Community mobilisation as an activity in its own right was rarely documented and while most projects successfully engaged communities, few progressed to involvement, community ownership or sustainability. Only a few interventions had evolved to facilitate collective action through formal democratic structures (stage 3). These reported improved sexual negotiating power and community solidarity, and positive behavioural and clinical outcomes. Sustainability of many projects was weakened by disunity within transient communities, variable commitment of programmers, low human resource capacity and general resource limitations.

Conclusions

Most FSW SRH projects in Africa implemented participatory processes consistent with only the earliest stages of community empowerment, although isolated projects demonstrate proof of concept for successful empowerment interventions in African settings.

Systematic review of facility-based sexual and reproductive health services for female sex workers in Africa

Background

Several biological, behavioural, and structural risk factors place female sex workers (FSWs) at heightened risk of HIV, sexually transmitted infections (STIs), and other adverse sexual and reproductive health (SRH) outcomes. FSW projects in many settings have demonstrated effective ways of altering this risk, improving the health and wellbeing of these women. Yet the optimum delivery model of FSW projects in Africa is unclear. This systematic review describes intervention packages, service-delivery models, and extent of government involvement in these services in Africa.

Methods

On 22 November 2012, we searched Web of Science and MEDLINE, without date restrictions, for studies describing clinical and non-clinical facility-based SRH prevention and care services for FSWs in low- and middle-income countries in Africa. We also identified articles in key non-indexed journals and on websites of international organizations. A single reviewer screened titles and abstracts, and extracted data from articles using standardised tools.

Results

We located 149 articles, which described 54 projects. Most were localised and small-scale; focused on research activities (rather than on large-scale service delivery); operated with little coordination, either nationally or regionally; and had scanty government support (instead a range of international donors generally funded services). Almost all sites only addressed HIV prevention and STIs. Most services distributed male condoms, but only 10% provided female condoms. HIV services mainly encompassed HIV counselling and testing; few offered HIV care and treatment such as CD4 testing or antiretroviral therapy (ART). While STI services were more comprehensive, periodic presumptive treatment was only provided in 11 instances. Services often ignored broader SRH needs such as family planning, cervical cancer screening, and gender-based violence services.

Conclusions

Sex work programmes in Africa have limited coverage and a narrow scope of services and are poorly coordinated with broader HIV and SRH services. To improve FSWs’ health and reduce onward HIV transmission, access to ART needs to be addressed urgently. Nevertheless, HIV prevention should remain the mainstay of services. Service delivery models that integrate broader SRH services and address structural risk factors are much needed. Government-led FSW services of high quality and scale would markedly reduce SRH vulnerabilities of FSWs in Africa.

Estimating the size of the female sex worker population in Kenya to inform HIV prevention programming

Background

The high burden of HIV infections among female sex workers (FSW) in sub-Saharan Africa has been long recognised, but effective preventive interventions have largely not been taken to scale. We undertook a national geographical mapping exercise in 2011/2012 to assess the locations and population size of FSW in Kenya, to facilitate targeted HIV prevention services for this population.

Methods and Findings

We used a geographical mapping approach, consisting of interviews with secondary key informants to identify “hot” spots frequented by FSW, their operational dynamics and the estimated numbers of FSW in those spots. This was followed by validation of the estimates through interviews with FSW at each spot identified. The mapping covered Nairobi, the capital city of Kenya, and 50 other major urban centres. In total, 11,609 secondary key informant interviews were conducted to identify FSW spots. Further, a total of 6,360 FSW were interviewed for spot validation purposes. A total of 10,670 spots where FSW congregate were identified. The estimated FSW population in all the towns mapped was 103,298 (range 77,878 to 128, 717). Size estimates in the towns mapped were extended to smaller towns that were not mapped, using a statistical model. The national urban FSW population estimate was 138,420 (range 107, 552 to 169, 288), covering all towns of over 5,000 population. We estimated that approximately 5% of the urban female population of reproductive age in Kenya could be sex workers, which is consistent with previous estimates from other sub-Saharan African countries.

Conclusions

This study provides the first national level data on the size of the FSW population in Kenya. These data can be used to enhance HIV prevention programme planning and implementation for FSW, to form the basis for impact evaluations, and to improve programme coverage by directing efforts to locations with the greatest need.

Prevalence of HIV and other sexually transmitted infections among female sex workers in Kisumu, Western Kenya, 1997 and 2008

Background

In 1997, a survey in Kisumu found a prevalence of HIV infection among female sex workers (FSW) of 75%. Only 50% reported using a condom with the last client. In 2008, we conducted another survey to collect data to inform an intervention targeting FSW in Kisumu.

Methods

In 2008 FSW were recruited by respondent-driven sampling. Women completed a questionnaire and were tested for HIV and other sexually transmitted infections (STIs). Multiple logistic regression analysis was done to explore factors associated with HIV-infection, and with condom use. Prevalence of HIV infection was compared in the two surveys from 1997 and 2008. Multivariate analysis was used to assess whether a change in HIV prevalence between the two surveys could be explained by changes in socio-demographic characteristics and/or behavioral factors.

Results

481 FSW participated in the 2008 study. HIV prevalence was 56.5% (95% CI 52.0–61.6). Factors independently associated with HIV were age older than 29 years; being a widow; STI treatment in the past year; herpes simplex virus Type-2 infection; bacterial vaginosis; and trichomoniasis. Condom use with last client was reported by 75.0% (95% CI 70.9–78.9). Predictors of condom use with the last client were age older than 29 years; higher price paid by last client; ever having been tested for HIV. Predictors of unprotected sex were being drunk during last sex act; usually having sex during menses; and STI treatment in the past year. The odds ratio of HIV infection associated with year of survey was 0.49 (95% CI 0.33–0.75) after adjusting for socio-demographic and behavioral factors.

Conclusions

The prevalence of HIV among FSW in Kisumu was found to be lower in 2008 than in 1997, while reported condom use was higher. However, access to HIV/STI prevention and care services needs to improve to further decrease HIV transmission between FSW and their clients.

Socio-demographic characteristics and behavioral risk factors of female sex workers in sub-saharan Africa: a systematic review

Sex work remains an important contributor to HIV transmission within early, advanced and regressing epidemics in sub-Saharan Africa, but its social and behavioral underpinnings remain poorly understood, limiting the impact of HIV prevention initiatives. This article systematically reviews the socio-demographics of female sex workers (FSW) in this region, their occupational contexts and key behavioral risk factors for HIV. In total 128 relevant articles were reviewed following a search of Medline, Web of Science and Anthropological Index. FSW commonly have limited economic options, many dependents, marital disruption, and low education. Their vulnerability to HIV, heightened among young women, is inextricably linked to the occupational contexts of their work, characterized most commonly by poverty, endemic violence, criminalization, high mobility and hazardous alcohol use. These, in turn, predict behaviors such as low condom use, anal sex and co-infection with other sexually transmitted infections. Sex work in Africa cannot be viewed in isolation from other HIV-risk behaviors such as multiple concurrent partnerships-there is often much overlap between sexual networks. High turn-over of FSW, with sex work duration typically around 3 years, further heightens risk of HIV acquisition and transmission. Targeted services at sufficiently high coverage, taking into account the behavioral and social vulnerabilities described here, are urgently required to address the disproportionate burden of HIV carried by FSW on the continent.

Evaluating HIV prevention effectiveness: the perfect as the enemy of the good

There is a need to better understand the effectiveness of HIV-prevention programs. Cluster randomized designs have major limitations to evaluate such complex large-scale combination programs. To close the prevention evaluation gap, alternative evaluation designs are needed, but also better articulation of the program impact pathways and proper documentation of program implementation. Building a plausible case using mixed methods and modeling can provide a valid alternative to probability evidence. HIV prevention policies should not be limited to evidences from randomized designs only.

Burden of HIV among female sex workers in low-income and middle-income countries: a systematic review and meta-analysis

BACKGROUND

Female sex workers are a population who are at heightened risk of HIV infection secondary to biological, behavioural, and structural risk factors. However, three decades into the HIV pandemic, understanding of the burden of HIV among these women remains limited. We aimed to assess the burden of HIV in this population compared with that of other women of reproductive age.

METHODS

We searched PubMed, Embase, Global Health, SCOPUS, PsycINFO, Sociological Abstracts, CINAHL (Cumulative Index to Nursing and Allied Health Literature), Web of Science, and POPLine for studies of female sex workers in low-income and middle-income countries published between Jan 1, 2007, and June 25, 2011. Studies of any design that measured the prevalence or incidence of HIV among female sex workers, even if sex workers were not the main focus of the study, were included. Meta-analyses were done with the Mantel-Haenszel method with a random-effects model characterising an odds ratio for the prevalence of HIV among female sex workers compared with that for all women of reproductive age.

FINDINGS

Of 434 selected articles and surveillance reports, 102 were included in the analyses, representing 99,878 female sex workers in 50 countries. The overall HIV prevalence was 11·8% (95% CI 11·6-12·0) with a pooled odds ratio for HIV infection of 13·5 (95% CI 10·0-18·1) with wide intraregional ranges in the pooled HIV prevalence and odds ratios for HIV infection. In 26 countries with medium and high background HIV prevalence, 30·7% (95% CI 30·2-31·3; 8627 of 28,075) of sex workers were HIV-positive and the odds ratio for infection was 11·6 (95% CI 9·1-14·8).

INTERPRETATION

Although data characterising HIV risk among female sex workers is scarce, the burden of disease is disproportionately high. These data suggest an urgent need to scale up access to quality HIV prevention programmes. Considerations of the legal and policy environments in which sex workers operate and actions to address the important role of stigma, discrimination, and violence targeting female sex workers is needed.

FUNDING

The World Bank, UN Population Fund.

Estimating the Size of the Methamphetamine-Using Population in New York City Using Network Sampling Techniques

As part of a recent study of the dynamics of the retail market for methamphetamine use in New York City, we used network sampling methods to estimate the size of the total networked population. This process involved sampling from respondents' list of co-use contacts, which in turn became the basis for capture-recapture estimation. Recapture sampling was based on links to other respondents derived from demographic and "telefunken" matching procedures-the latter being an anonymized version of telephone number matching. This paper describes the matching process used to discover the links between the solicited contacts and project respondents, the capture-recapture calculation, the estimation of "false matches", and the development of confidence intervals for the final population estimates. A final population of 12,229 was estimated, with a range of 8235 - 23,750. The techniques described here have the special virtue of deriving an estimate for a hidden population while retaining respondent anonymity and the anonymity of network alters, but likely require larger sample size than the 132 persons interviewed to attain acceptable confidence levels for the estimate.