HIV Serosorting among Men Who Have Sex with Men: Population-Level Impacts of Partner Selection and Sexual Behavior

Susan L. Cassels, University of Washington
Timothy W. Menza, University of Washington
Steven M. Goodreau, University of Washington

Serosorting is the practice of preferentially having sex with partners of concordant HIV status, or of selectively using condoms with HIV discordant partners. Despite many potential benefits, serosorting may be risky if perceived and actual HIV status differs: a perceived HIV-negative individual may in fact be recently infected, and thus highly infectious. We developed a deterministic mathematical model of HIV transmission dynamics to study how serosorting affects HIV prevalence among men who have sex with men in Seattle, Washington. Predicted population-level HIV prevalence decreases when the odds of serosorting are increased in the mathematical model. In our baseline model with serosorting, HIV prevalence is 16.0%, and increased to 24.5% without reported levels of serosorting. However, our findings depend on rates of condom use, mean anal sex contact rates and HIV testing in the population. Under realistic scenarios of sexual behavior and testing frequency, serosorting can be an effective harm-reduction strategy.