Social networks of men who have sex with men and their implications for HIV/STI interventions: results from a cross-sectional study using respondent-driven sampling in a large and a small city in Tanzania

Objective: Men who have sex with men (MSM) in sub-Saharan Africa remain hidden and hard to reach for involvement in HIV and sexually transmitted infection (STI) services. The aim of the current study was to describe MSM social networks in a large and a small Tanzanian city in order to explore their utility for peer-based healthcare interventions. Methods: Data were collected through respondentdriven sampling (RDS) in Dar es Salaam (n = 197) and in Tanga (n = 99) in 2012 and 2013, using 5 and 4 seeds, respectively. All results were adjusted for RDS sampling design. Results: Mean personal network size based on the number of MSM who were reported by the participants, as known to them was 12.0 +/- 15.5 in Dar es Salaam and 7.6 +/- 8.1 in Tanga. Mean actual RDS network size was 39.4 +/- 31.4 in Dar es Salaam and 25.3 +/- 9.7 in Tanga. A majority (97%) reported that the person from whom they received the recruitment coupon was a sexual partner, close friend or acquaintance. Homophile in recruitment patterns (selective affiliation) was present for age, gay openness, and HIV status in Dar es Salaam, and for sexual identification in Tanga. Conclusions: The personal network sizes and existence of contacts between recruiter and referral indicate that it is possible to use peer-driven interventions to reach MSM for HIV/STI interventions in larger and smaller sub-Saharan African cities. The study was reviewed and approved by the University of Texas Health Science Center's Institutional Review Board (HSC-SPH-10-0033) and the Tanzanian National Institute for Medical Research (NIMR/HQ/R.8a/Vol.IX/1088).