Increasing prevalence of unprotected anal intercourse with serodiscordant casual partners among HIV-negative and positive gay men in Sydney, Australia: no evidence of ‘bug chasing’
Background: We examined recent changes in serodiscordant unprotected anal intercourse with casual partners (UAIC) among HIV-negative and positive gay men and associated behaviours.
Methods: In two open community cohorts of HIV-negative and HIV-positive gay men in Sydney, Australia, participants provided the number of HIV-positive, HIV-negative, or unknown-serostatus casual partners and the number of UAI acts with them during the six months prior to interview. We report time trends between 2003 and 2006 in serodiscordant UAIC and the unadjusted Odds Ratios (Unadj OR) with 95% Confidence Intervals (95% CIs) for the associations between selected factors and serodiscordant UAIC measured in population-averaged longitudinal logistic-regression models.
Results: The proportion of men with serodiscordant casual partners significantly increased (p<0.01) in both cohorts. The prevalence of serodiscordant UAIC also increased among HIV-negative men (p trend= 0.04) but not among HIV-positive men (insignificant increase, p=0.85). During 2003-2006, 73 of 549 HIV positive and 82 of 1299 HIV negative men reported, in at least one interview, serodiscordant UAIC; only 6 and 4 men, respectively, reported it in each interview. Serodiscordant UAIC was reported in 10.7% and 3.3% of interviews, respectively. Age, not having a regular partner, high number of sex partners, use of the Internet, saunas and sex clubs to find sex partners, monthly use of Viagra, other party drugs, injecting any drug, and esoteric sex practices were significantly associated with serodiscordant UAIC. In HIV-positive men, undetectable viral load was not associated with serodiscordant UAIC.
Conclusions: Although proportions are small, the significant increase in prevalence of serodiscordant UAIC may play a role in recent HIV seroconversions. It is possible that the increase in serodiscordant UAIC may be an unintended consequence of a similar increase in serosorting among both HIV-negative and positive men. The association of serodiscordant UAIC with other known risk factors contributes to our understanding of HIV risk-taking.
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