Abstract
HIV seroconversions and sexually transmitted diseases (STDs) are often clustered in social networks within community populations. The present study was carried out among men who have sex with men in Russia, where a major HIV epidemic is unfolding, and where social networks have played a historically important role. In all, 38 social networks were recruited into the study, and members of all networks (n = 187) completed risk behaviour assessments and were tested for STDs. About 17% of participants had STDs, and 10% of men had syphilis. Over 64% of men had recent unprotected anal intercourse (UAI), including 51% who did so with main partners, 30% who did so with casual partners, and 32% who had UAI with multiple male partners. The strongest predictor of all risk behaviour indicators and STDs was the social network, to which an individual belonged, supplemented by peer norm perceptions and intentions to practise safer sex. There was a high level of correspondence in behaviour between the social leader of a network and its other members. Social networks should be directly targeted in HIV prevention efforts.