The impact of sex partners' HIV status on HIV seroconversion in a prospective cohort of injection drug users

Abstract

Objective and design: The identification of individuals at highest risk of HIV infection is critical for targeting prevention strategies. We evaluated the HIV status of the sex partners of injection drug users (IDUs) and rates of subsequent HIV seroconversion among a prospective cohort study of IDUs.

Methods: We performed an analysis of the time to HIV infection among baseline HIV-negative IDUs enrolled in the Vancouver Injection Drug Users Study. IDUs were stratified based on whether or not they reported having an HIV-positive sex partner. Kaplan-Meier methods were used to estimate cumulative HIV incidence rates, and Cox regression was used to determine adjusted relative hazards (RHs) for HIV seroconversion.

Results: Of 1013 initially HIV-negative IDUs, 4.8% had an HIV-positive partner at baseline. After 18 months, the cumulative HIV incidence rate was significantly elevated among those who reported having an HIV-positive sex partner (23.4% vs. 8.1%; log-rank P < 0.001). In a Cox regression model adjusting for all variables that were associated with the time to HIV infection in univariate analyses, including drug use characteristics, having an HIV-positive sex partner (RH = 2.42 [95% confidence interval: 1.30 to 4.60]; P = 0.005) remained independently associated with time to HIV seroconversion.

Conclusions: Having an HIV-positive sex partner was strongly and independently associated with seroconversion after adjustment for risk factors related to drug use. Our findings may aid public health workers in their efforts to identify IDUs who should be targeted with education and prevention efforts and indicate the need for ongoing development of prevention interventions for IDU sex partners who are HIV discordant.