Using virtual sites for population size estimates of men who have sex with men in urban Tanzania: a feasibility study

Abstract Background Globally, men who have sex with other men (MSM) increasingly use virtual platforms for networking and soliciting sexual partners due to unrelenting stigma and discrimination. However, most studies estimating the MSM population for HIV prevention coverage in sub-Saharan Africa focus on physical sites, failing to account for MSM using virtual platforms. This study aimed to examine the feasibility of estimating the MSM population using virtual spaces in Tanzania. Methods MSM recruited from civil society organisations collected data on two levels: First, a participatory ranking method involving key informants was used to identify virtual sites, and on each site, they listed all profiles used by MSM in selected towns. Secondly, research assistants logged in to those platforms three times a day (morning, afternoon, and evening) and counted all those who were active online at every time point for seven days. Those online were invited to participate in a voluntary short survey. The number of profiles recorded was generated by aggregating the virtual site profiles for MSM registered daily. Data collected in the short survey were then applied as correction factors to adjust for MSM counted twice or more on different days of the week and for those who may have been missed in the survey. Results A total of 4,480 active profiles were observed. Of the 4,480 unadjusted profiles, only 2,429 were unique. 598 male virtual site users aged 18 + years were interviewed to collect data on correction factors. Approximately 91% of participants on virtual sites also visited physical venues. Nearly 90% of participants in the short survey used virtual sites for socialising and sexual networking several times a week. Conclusion This study shows that virtual mapping is a feasible strategy to capture estimates of MSM who cannot be counted through venue-based approaches, especially in contexts where MSM face legal and societal stigmatisation and discrimination.