Seroadaptive behaviours among men who have sex with men in San Francisco: the situation in 2008

To assess changes in seroadaptive behaviours among men who have sex with men (MSM) in San Francisco over the past 4 years.

461 MSM were recruited in 2008 as the second wave of the US National HIV Behavioural Surveillance (NHBS) survey in San Francisco. Participants were classified into patterns of seroadaptive behaviours based on reported sexual practices (ie, episodes of insertive and receptive anal sex), condom use, HIV serostatus and partners' serostatus for up to five partners in the preceding 6 months. The prevalence of seroadaptive behaviours was compared with the first wave of NHBS, which used identical methods in 2004.

In 2008, 33.7% of HIV-negative and 18.9% of HIV-positive MSM used condoms 100% of the time; nearly half (48.0%) of HIV-negative MSM and two-thirds (66.7%) of HIV-positive MSM had unprotected anal intercourse (UAI). Collectively, seroadaptive behaviours comprised the most common form of risk management; 40.5% of HIV-negative MSM and 51.1% of HIV-positive MSM engaged in some form of seroadaptation, the most common being 'pure serosorting' (all UAI with same serostatus partners) reported by 27.5% of HIV-negative MSM and 22.2% of HIV-positive MSM. None of these behaviours were significantly different from their corresponding measures in 2004.

Seroadaptation continues to describe the prevailing form of sexual risk management for MSM in San Francisco, suggesting that these behaviours are not novel and require careful measurement to gauge the true potential for the spread of HIV, and nuanced prevention messages to reduce risk.