Effect of HSV-2 serostatus on the acquisition of HIV by young men: results of a longitudinal study conducted in Orange Farm (South Africa)

Background: The objectives of this study were to assess the role of HSV-2 status, first, on HIV acquisition by young men and secondly, on the protective effect of male circumcision on HIV acquisition. Methods: We used data collected during a male circumcision trial conducted in Orange Farm (South Africa). We estimated adjusted incidence rate ratios (aIRR) using survival analysis and background characteristics, HSV-2 status, male circumcision status and sexual behavior as covariates. Results: Compared to HSV-2 negative participants, HIV aIRR was 3.3 [95%CI, 1.5–7.4] P=.004 among those who were HSV-2 positive at enrollment and 7.0 [95%CI, 3.9–12.4] P<.001 among those who became HSV-2 positive during follow-up. The population fraction of HIV incident cases attributable to HSV-2 was 27.8% [95%CI, 17.7%–37.2%]. The intention-to-treat protective effect of male circumcision on HIV acquisition was the same among HSV-2 positive and HSV-2 negative men (0.38vs.0.37; P = .93). Conclusions: This study shows that HSV-2 has a substantial impact on HIV acquisition among young South African men. It suggests that HSV-2 infection enhances HIV acquisition and is responsible for about a quarter of HIV incident cases. However, the protective effect of male circumcision on HIV acquisition appears independent of HSV-2 serostatus.