Background: Epidemics of HIV in men who have sex with men (MSM) continue to expand in most low-, middle-, and upper-income countries in 2013. High rates of new infection are consistently found among young MSM globally. A review of HIV prevalence and incidence, individual- and network-level risks for HIV, and of prevention and care options, suggests that the high probability of transmission per act through receptive anal intercourse, and sex role versatility among MSM, play central roles in explaining disproportionate disease burdens. HIV can be transmitted through large MSM networks at great speed. Molecular epidemiologic data show marked clustering of HIV in MSM networks, and higher rates of dual and multiple variant infection in these men than in heterosexual networks in the same populations. Prevention strategies which lower biological transmission and acquisition risks, including those based on use of ARV, offer promise for epidemic control, but are limited by structural factors including discrimination, criminalization, and barriers to health-care access for MSM which much also be addressed.

Conclusions: Sub-epidemics, including among minority MSM in the US and UK, are particularly severe and will require targeted efforts. Community leadership, engagement, and empowerment are likely to be key to success. To address the expanding epidemics of HIV in MSM will require continued research, political will, structural reform, community engagement, and strategic planning and programming, but it can and must be done.