A Success for Serosorting

New HIV infections among gay and bisexual men in San Francisco have been cut in half during the past four years, and some health officials say efforts by HIV-positive men to engage in sex only with other seropositive men could be behind the decrease. According to a Centers for Disease Control and Prevention study, the annual HIV incidence rate among the city's men who have sex with men dropped from 2.2% to 1.2%; similar studies by the Stop AIDS Project and city health clinics confirm the decrease. CDC researchers and San Francisco AIDS experts say that 'serosorting'--in which individuals deliberately seek out sex partners of the same HIV serostatus--is playing a key role in the decrease. Successful antiretroviral therapy that lowers viral levels and makes HIV transmission more difficult and increased efforts to get gay men tested also are contributing factors, experts say.