Background To describe HSV-2 prevalence, incidence and their correlates among stable HIV-1 discordant heterosexual couples enrolled in an HIV-1 prevention cohort study in Nairobi, Kenya.

Methods Between 2007 and 2009, 469 HIV-1 discordant couples were recruited from VCT centers, and were followed up quarterly for up to 2 years. Clinical staff administered a questionnaire assessing socio-demographics, behaviour, and biological characteristics. HSV-2 status was assessed using Focus Herpe-Select2 HSV IgG ELISA. Correlates of HSV-2 infection at enrolment, and during follow-up were identified by logistic regression and Cox proportional hazards analysis respectively.

Results Of the couples, 189 (40%) were HSV-2 concordant positive, 114 (24%) were HSV-2 discordant, and 85 (18%) were concordant negative. The incidence of HSV-2 infection was 8.7 cases/100 person-years. 19 (17%) individuals in an initially HSV-2 discordant partnership and 11 (13%) in an initially HSV-2 concordant negative partnership acquired HSV-2 during follow-up. Of these 11 individuals, 9(81%) were the HIV-1 positive index case in the HIV-1 discordant relationship. In a multivariate analysis, HSV-2 prevalence at baseline was significantly associated with female gender (OR 4.4; (95% CI 2.9 to 6.7)), having an HSV-2 positive partner (OR 7.6; (95% CI 5.1 to 11.2)), being HIV positive (OR 2.2; (95% CI 1.5 to 3.1)), increasing age (OR 1.08; (95% CI 1.05 to 1.1)), and older age at sexual debut was protective (OR 0.87; (95% CI 0.83 to 0.93)). HSV-2 incidence during follow-up was significantly associated with female gender (HR 3.5; (95% CI 1.6 to 8.0)), having an HSV-2 positive partner (HR 4.9; (95% CI, 2.0 to 9.9)), and history of any other STI (HR 2.6; (95% CI 1.3 to 5.8)).

Conclusions This is the first large study to report the prevalence and incidence of HSV-2 among sexual partners who are in a stable HIV-1 discordant relationship. Female gender, a history of any other STI, and having an HSV-2 positive partner were associated with an increased risk of acquiring HSV-2. 11 individuals a majority of them with HIV acquired HSV-2 during follow-up despite being in HSV-2 concordant negative relationship at enrolment. The high incidence of HSV-2 in couples who were initially HSV-2 concordant negative or HSV-2 discordant highlights the dire need for continuing comprehensive STD prevention programs particularly among high risk population Sub-Saharan Africa.