While some population-based surveys have found increased risk of HIV infection among men who report same-sex behavior [11], most behavioral and epidemiological studies with African MSM as the target population have relied on convenience or snowball samples of men who self-identify as homosexual within their cultural contexts [3, 5, 12–14]. While these studies have been an important to beginning investigations of the HIV epidemic among MSM where same sex behavior is stigmatized or illegal, more hidden, non-homosexually identified subpopulations of MSM may be underrepresented in these samples. The sexual behaviors and HIV prevalence of such men are important to understanding patterns of HIV transmission among MSM generally. Furthermore, selection bias limits the generalizability of results. The respondent driven sampling (RDS) methodology described by Heckathorn has the potential to reach more deeply into hidden MSM sub-populations and, by limiting recruitment and tracking the personal network size of participants, to minimize biases inherent in convenience and snowball sampling [15, 16]. To date, only one published study of MSM in Africa has used RDS recruitment and estimation, but it was not able to measure HIV prevalence [4].

This paper presents results from The Soweto Men’s Study, which assessed HIV prevalence and risk factors in a population of sexually active MSM in Soweto, South Africa, using RDS recruitment and analysis methods. Soweto is a peri-urban “township” roughly 15 km southwest of central Johannesburg with a population estimated between 1.5 and 3 million. The MSM population includes men who openly identify as “gay” or “bisexual”, as well as many who identify as “straight” to keep their same-sex behaviors hidden from family, friends, or female partners. It is important to note that the “gay” identity claimed by Soweto MSM does not map neatly onto “western” or “global” gay identity as it is commonly understood. In preliminary ethnographic work, MSM associated gay identity with feminine gender identity—though it is important to note that “transgender” is not an identity category that any of our participants claimed.

The study questionnaire was based on a behavioral instrument used previously with this population [5]. Questions included standard demographic indicators; regular female and male sexual partnerships (someone the participant “lived with, saw a lot, and felt a special emotional commitment to for 3 months or more”); circumcision status; history of incarceration; age and condom use at sexual debut with men and women; history of coerced sex; transactional sex with men and women (sex in exchange for “expensive gifts,” “money, food, or a place to sleep,” and “drugs or alcohol”); and drug and alcohol use. The Alcohol Use Disorders Identification Test (AUDIT) was used to characterize drinking behavior [17]. AUDIT assessments include frequency of drinking, amount of alcohol consumed when drinking, and perceptions of self and others about drinking; a score greater than 9 indicates “problem drinking.” The survey also asked partner-by-partner sexual behavior and condom use questions for up to five partners within the prior 6 months. Participants reported the sex of their partners (and sexual identity of male partners), whether regular (e.g. husband/wife, boyfriend/girlfriend) or casual (e.g. “one night stand”), number of times vaginal or anal sex, position in anal sex, and number of protected acts. Unprotected sex (vaginal and anal) was determined by subtracting number of protected sex acts from number of sex acts; all responses greater than zero were coded unprotected. Finally, participants answered questions about their history of STI symptoms and treatment in the last 12 months, HIV testing history, and perceived HIV status.

HIV status was determined through rapid antibody testing on blood samples collected through voluntary counseling and testing (VCT), linked to the participants’ behavioral data by study identification number. After completing the survey, we offered all participants VCT, for which they provided separate informed consent. Trained counselors provided pre- and post-test counseling. After pre-test counseling, a nurse drew 5 ml of blood from each participant. Participants could elect to receive their results that day, or to return within 3 months of their study visit. Men who received a positive result were referred to clinical care within the PHRU pending the result of CD4 testing of their blood samples. Men with CD4 cell counts less than 200/mm³ were provided with antiretroviral (ARV) treatment free of charge.

Alcohol was the most commonly used substance (Table 2), with 87.9% reporting that they drank at least once per month, and 54.5% reporting 10 or more drinks on a typical day of drinking; 75.9% of AUDIT scores indicated problem drinking. Other substance use was less common; 25.0% of the sample had used marijuana, and use of stimulants including ecstasy, cocaine, methcathinone, and methamphetamines was rare, as was injection drug use.

Sexual health indicators for this population were mixed. Few reported STI symptoms in the last year. Although 37.9% had ever tested, recent HIV testing (i.e. within the last 6 months) was uncommon. Prior to testing in the study, most men perceived that they were HIV-negative (57.2%); less than 1% of MSM perceived that they were HIV-positive. The unadjusted results of HIV testing showed that 20.6% of the sample was HIV-positive, with 18.8% declining to give a blood sample; of the 307 men who consented to VCT, 115 (37.5%) declined to receive their results on the day of their study visit, and none returned within 6 months to collect them.

In reporting this finding, we recognize that gay identity is not a behavior, although in township MSM communities gay identity is itself highly correlated with the exclusive practice of RAI, and conversely, self-identifying as bisexual or a straight MSM was highly correlated with the exclusive practice of insertive anal intercourse (IAI) with male partners [5]. Since gay-identified men are also the most visible of MSM in township communities, this finding indicates that it is possible and necessary to begin working immediately with gay-identified men on HIV prevention and treatment, focused not only on individual behaviors, but the disadvantageous structural and socio-cultural contexts that influence their behaviors. Unlike other sub-Saharan African countries, there are no legal barriers to working with gay communities in South Africa.

The Soweto Men’s Study is also, to our knowledge, one of the first studies of MSM in Africa to have applied the RDSAT-generated weight outcomes described by Heckathorn [18] to estimate HIV prevalence and to develop multivariable model of HIV risk factors, and the first with an HIV prevalence outcome to account for missing outcome data through multiple imputation. That the imputed model’s HIV prevalence estimates were between the two extreme possibilities gives us confidence that the procedure has resulted in a reasonable initial HIV prevalence estimate for this population. Given RDS’s popularity with studying MSM populations in sub-Saharan Africa, future behavioral and HIV surveillance studies using RDS may need to follow similar procedures to account for missing HIV data. Other studies have found that MSM who are socially vulnerable may be reluctant to test [12], and that many MSM have prior negative experiences with HIV VCT [20]. It is therefore understandable that MSM may decline to test even in a study setting that guaranteed access to medical care.

Several studies have noted the association between alcohol consumption and sexual risk behaviors [21–23] Our sample was quite homogenous in its drinking behavior, and thus we did not detect a statistically significant association with UAI or HIV infection; we do not conclude that alcohol consumption plays no part in HIV transmission among MSM. On the contrary, purchasing alcohol in exchange for sex with other men predicted HIV infection—and was the only form of transactional sex between men with a significant effect. This speaks to the complex role that substance use and sexual exchange play in the lives of township MSM. Better understanding how all of these factors may contribute to MSM’s HIV risk will be important to intervention efforts.

A large number of participants also reported having a regular female partner, and counted at least one woman among their last five partners. Although female partnerships and UVI were associated with lower HIV risk, the comparison group in each case is composed overwhelmingly of gay-identified men who practice RAI with other men, whose risk is much higher. It is important to note that relatively high rates of self-reported UVI (45.6%) and UIAI with men (28.0%) in this population provide ample opportunity for HIV transmission to take place, and suggests that the heterosexual and MSM epidemics are behaviorally linked. MSM who also have sex with women keep their identities and behaviors hidden and are therefore difficult to target with same-sex specific HIV prevention messaging aimed at gay men; in the absence of information this group may be inadvertently increasing the long-term risk of HIV infection to themselves as well as their male and female partners.

Circumcision was associated with lower HIV prevalence. Given that most MSM in our sample reported practicing IAI exclusively, we conclude that there may be a protective association for MSM in South Africa for men who are consistently the insertive partners in anal sex with men. Although a meta-analysis of observational studies of circumcision in MSM populations by Millet et al. could not detect a consistent protective effect, the authors did find a non-significant reduction in odds in settings with less than 50% circumcision prevalence, and concluded that more data on MSM who engage primarily in IAI would be helpful [24]. Given the potential for circumcision to decrease HIV transmission at the population level, and that many MSM who are insertive partners with men also have sex with women, this association should continue to be explored in further observational research with MSM throughout the region.

Our study has several limitations. RDS studies of MSM have been critiqued for overstating claims to unbiased population estimates because the samples actually recruited may not fully represent the underlying population, even after adjustment [25]. Although we attempted systematically to select seeds that would produce a well-networked and diverse sample, it is possible that men who are unemployed and who have lower socioeconomic status (SES) and educational achievement are not well networked with better educated and resourced MSM. Thus unemployed men of lower SES may be overrepresented in our sample. However, our results are likely representative of the most socially vulnerable MSM whose limited income, mobility, and economic opportunity may also limit their access to HIV prevention information, condoms and latex-compatible lubricant, and high-quality health services. It is notable that although black race and Soweto residence were not explicit inclusion criteria, the chains did not leave Soweto except in the case of one Coloured participant, suggesting that the legacy of apartheid continues to limit Soweto MSM’s geographic and social mobility. It is also possible that the offer of VCT may have operated both as an additional recruitment incentive [26, 27] as well as a disincentive to participating altogether, biasing the results in ways that would be difficult to account for. The interviewer-administered questionnaires may have introduced social desirability bias with respect to self-report of sensitive sexual behaviors, including drug use, receptive AI, and/or unprotected AI. In addition, the multiple imputation procedure we followed for missing HIV results is untested, and to the extent that risk behavior may have been underreported, our imputation method would bias our prevalence estimate towards the extreme possibility of non-testers being HIV-negative. We acknowledge that our adjusted results are likely a conservative estimate of HIV prevalence in the target population.