Is sexual serosorting occurring among HIV-positive injection drug users? Comparison between those with HIV-positive partners only, HIV-negative partners only, and those with any partners of unknown status.

Using baseline data from a multi-site, randomized controlled study (INSPIRE), we categorized 999 HIV-positive IDUs into three groups based on serostatus of their sex partners. Our data provide some evidence for serosorting occurring in our sample; about 40% of the sample had sex exclusively with HIV-positive partners, and about half of them reported having unprotected sex with these partners. Twenty per cent had sex exclusively with HIV-negative partners; their sexual behaviors tended to be least risky with about two-thirds reporting their sex was protected. However, we also found that another 40% had at least one partner of unknown HIV status and sexual and drug risk was the highest among them. They were also least empowered, showing attributes that may undermine HIV prevention. Some of these findings are consistent with findings from MSM studies, suggesting that partner selection practices are similar between primarily heterosexual IDUs and MSM.