HIV-1 transmission among HIV-1 discordant couples before and after the introduction of antiretroviral therapy

Objective: To evaluate the impact of antiretroviral therapy (ART) on HIV-1 transmission rates among HIV-1 discordant couples in Rakai, Uganda. Design: Observational cohort study. Methods: HIV-1 discordant couples were retrospectively identified between 2004 and 2009. Study participants underwent annual screening for HIV-1 and were interviewed to evaluate risk behaviors. Participants were offered voluntary counseling and testing and provided with risk reduction counseling. Free ART was offered to participants with a CD4 cell count of 250 cells/μl or less or WHO stage IV disease. HIV-1 incidence and sexual risk behaviors were compared before and after the HIV-1-positive index partners started ART. Results: Two hundred and fifty HIV-1 discordant couples were followed between 2004 and 2009 and 32 HIV-1-positive partners initiated ART. Forty-two HIV-1 transmissions occurred over 459.4 person-years prior to ART initiation, incidence 9.2/100 person-years [95% confidence interval (CI) 6.59-12.36]. In 32 couples in which the HIV-1 index partners started ART, no HIV-1 transmissions occurred during 53.6 person-years. The 95% CI for the incidence rate difference was -11.91 to -6.38 (P = 0.0097). Couples reported more consistent condom use during ART use, but there was no significant difference in the number of sexual partners or other risk behaviors. Viral load was markedly reduced in persons on ART. Conclusion: HIV-1 transmission may be reduced among HIV-1 discordant couples after initiation of ART due to reductions in HIV-1 viral load and increased consistent condom use.