A new trend in the HIV epidemic among men who have sex with men, San Francisco, 2004-2011.

Background: In San Francisco, men who have sex with men (MSM) have historically comprised 90% of the HIV epidemic. It has been suggested that given the ongoing HIV transmission among this population, there is the possibility of a high-level endemic of HIV into the future. We report on the possibility of another phase in the HIV epidemic among MSM in San Francisco.

Methods: Behavioral surveillance systems monitor HIV prevalence, HIV incidence, and behaviors among populations at high risk for HIV infection. Among MSM, time-location sampling is used to obtain samples for standardized behavioral surveys, HIV-antibody and incidence testing. We analyzed National HIV Behavioral Surveillance data from MSM sampled in 2004, 2008, and 2011.

Results: Three hundred eighty-six, 521, and 510 MSM were enrolled in each of the waves. Only slight changes were seen in demographics over time. We detected significant declines in unrecognized HIV infection and methamphetamine use, a significant increase in HIV testing in the past 6 months, and no changes in HIV prevalence, history of gonorrhea infection, or having multiple sex partners. Among HIV-infected men, current antiretroviral treatment (ART) use seems to have risen from 2008 to 2011.

Conclusions: The trends of the last 7 years point to stable HIV prevalence as rising ART coverage results in improving survival coupled with decreasing incidence as ART use achieves viral load suppression at levels more than sufficient to offset ongoing sexual risk behavior. "Treatment as prevention" may be occurring among MSM in San Francisco.