Risk factors for HIV transmission among heterosexual discordant couples in South India.
To assess the risk factors associated with heterosexual HIV transmission among South Indian discordant couples enrolled in clinical care. A nested matched case-control study of serodiscordant couples in which the HIV-infected partner (index case) was enrolled in care. Demographic and clinical characteristics, sexual behaviours, CD4 cell count and plasma HIV-1 RNA loads were measured at enrollment and longitudinally over 12 months of follow-up. The study included 70 cases who seroconverted during study follow-up and 167 matched controls who remained persistently serodiscordant. The incidence of HIV infection among the initially seronegative partners was 6.52 per 100 person-years. Persistently discordant patients were more likely to have initiated highly active antiretroviral therapy (HAART) than patients in seroconverting relationships (62.9%vs. 42.9%) (P=0.001). Patients in seroconverting relationships had significantly higher plasma viral loads (PVLs) than patients in discordant relationships at enrolment, at 6 months and at 12 months (P<0.05). Patients in seroconverting relationships were less likely to use condoms with their primary partners than patients in discordant relationships (P<0.05). Patients in relationships that seroconverted between 6 and 12 months were diagnosed more often with genital Herpes simplex than patients in discordant relationships (P=0.001). In the univariate and multivariate logistic regression, the following variables were associated with seroconversion: PVL >100,000 [odds ratio (OR): 1.82; 95% confidence interval (CI): 1.1-2.8], non-disclosure of HIV status (OR: 5.5; 95% CI: 4.3-6.2) and not using condoms (OR: 2.8; 95% CI: 2.4-3.6). Couples-based intervention models are crucial in preventing HIV transmission to seronegative spouses. Providing early treatment for sexually transmitted infections, HAART and enhancing condom use and disclosure could potentially decrease the risk of HIV transmission within Indian married couples.