Unprotected anal intercourse between potentially HIV-serodiscordant men who have sex with men,San Francisco

BACKGROUND: Increasing trends in high-risk sexual behavior are noted among men who have sex with men (MSM) worldwide. Less information is available on unprotected sex between persons of different HIV serostatus. METHODS: From 1999 through 2001, volunteers of a community-based organization conducted interviews of 10,579 MSM at gay-oriented venues in San Francisco and in neighborhoods with high-volume MSM pedestrian traffic. The questionnaire recorded demographic and risk behavior information, including self-reported and partners' HIV serostatus. RESULTS: Potentially serodiscordant unprotected anal intercourse (UAI) with at least 2 anal sex partners was reported by 12.7% and increased from 11.0% in 1999 to 16.2% in 2001. Stratifying by self-reported HIV serostatus, 20.8% of HIV-positive respondents, 12.1% of HIV-negative respondents, and 13.4% of MSM who did not know or report their own HIV serostatus had potentially serodiscordant UAI. Older MSM of white race were more likely to report potentially serodiscordant UAI among HIV-positive respondents, whereas younger MSM of white race were more likely to report potentially serodiscordant UAI among HIV-negative respondents. Among those with unknown HIV serostatus, MSM of color were more likely to engage in potentially serodiscordant UAI. CONCLUSION: Recent increases in UAI among MSM in San Francisco are not only the result of increases in UAI between persons of the same HIV serostatus. Prevention messages must address disclosure of HIV serostatus to sexual partners specifically tailored to groups according to age, community, and HIV serostatus.