High HIV incidence and prevalence among young women in rural South Africa:Developing a cohort for intervention trials

Objective: To measure prevalence and model incidence of HIV infection. Sett ing: 2013 consecutive pregnant women attending public sector antenatal clin ics in 1997 in Hlabisa health district, South Africa. Historical seropreval ence data, 1992-1995. Methods: Serum remaining from syphilis testing was tested anonymously for a ntibodies to HIV to determine seroprevalence. Two models, allowing for diff erential mortality between HIV-positive and HIV-negative people, were used. The first used serial seroprevalence data to estimate trends in annual inc idence. The second, a maximum likelihood model, took account of changing fo rce of infection and age-dependent risk of infection, to estimate age-speci fic HIV incidence in 1997. Multiple logistic regression provided adjusted o dds ratios (OR) for risk factors for prevalent HIV infection. Results: Estimated annual HIV incidence increased from 4% in 1992/1993 to 1 0% in 1996/1997. In 1997, highest age-specific incidence was 16% among wome n aged between 20 and 24 years. in 1997, overall prevalence was 26% (95% co nfidence interval [CI], 24%-28%) and at 34% was highest among women aged be tween 20 and 24 years. Young age (<30 years; odds ratio [OR], 2.1; p = .001 ), unmarried status (OR 2.2; p = .001) and living in less remote parts of t he district (OR 1.5; p = .002) were associated with HIV prevalence in univa riate analysis. Associations were less strong in multivariate analysis. Par tner's migration status was not associated with HIV infection. Substantial heterogeneity of HIV prevalence by clinic was observed (range 17%-31%; test for trend, p = .001). Conclusions: This community is experiencing an explosive HIV epidemic. Youn g, single women in the more developed parts of the district would form an a ppropriate cohort to test, and benefit from, interventions such as vaginal microbicides and HIV vaccines.