Risk factors influencing HIV infection incidence in a rural African population: A nested case-control study

Background. Risk factors influencing the incidence of human immunodeficiency virus (HIV) infection were investigated in a case-control study nested within a community-randomized trial of treatment of syndromic sexually transmitted infections (STIs) in rural Tanzania. Methods. Case patients were persons who became HIV positive, and control subjects were randomly selected from among persons who remained HIV negative. For each sex, we obtained adjusted odds ratios (ORs) and population-attributable fractions (PAFs) for biomedical and behavioral factors. Results. We analyzed 92 case patients and 903 control subjects. In both sexes, the incidence of HIV infection was significantly higher in subjects with an HIV-positive spouse than in those with HIV-negative spouse ( men: OR, 25.1; women: OR, 34.0). The incidence of HIV infection was significantly higher in those who became positive for herpes simplex virus type 2 (HSV-2) ( men: OR, 5.60; women: OR, 4.76) and those who were HSV-2-positive at baseline ( men: OR, 3.66; women: OR, 2.88) than in subjects who were HSV-2 negative. In women, living elsewhere ( OR, 3.22) and never having given birth ( OR, 4.27) were significant risk factors. After adjustment, the incidence of HIV infection was not significantly associated with a history of injections or STIs in either sex. Conclusion. HSV-2 infection was the most important risk factor for HIV infection, which highlights the need for HSV-2 interventions in HIV infection control, and there were particularly strong associations with recent HSV-2 seroconversion. The PAF associated with having an HIV-positive spouse was low, but this is likely to increase during the epidemic.