Objective Adolescents in southern African high schools are a key population for HIV prevention interventions. We report on the prevalence of HIV, HSV-2 and pregnancy as indicators of high-risk sexual behaviour among high school students in rural KwaZulu-Natal.

Design Bio-behavioural cross-sectional survey.

Methods Students completed a self-administered structured, standardised demographic and sexual behavioural questionnaire. Dried blood spot specimens were collected for HIV and HSV-2 testing. Urine specimens were used for pregnancy testing in female students.

Results A total of 2675 (1423 females, 1252 males) consenting students were enrolled from 14 high schools between September and November 2010. The median age of students was 16 years (IQR 15–18). HIV prevalence was 1.4% (95% CI 0.9 to 1.9) in males and 6.4% (95% CI 4.6 to 8.3) in females (p<0.001). HSV-2 prevalence was 2.6% (95% CI 1.6 to 3.7) in males and 10.7% (95% CI 8.8 to 12.6) in females (p<0.001). Pregnancy prevalence was 3.6% (95% CI 2.6 to 4.5). Risk factors for prevalent HIV infection in female students included being over 18 years of age (adjusted OR (aOR)=2.67, 95% CI 1.67 to 4.27; p<0.001), prevalent HSV-2 infection (aOR=4.35, 95% CI 2.61 to 7.24; p<0.001), previous pregnancy (aOR=1.66, 95% CI 1.10 to 2.51; p=0.016) and experience of two or more deaths in the household in the previous year (aOR=1.97, 95% CI 1.13 to 3.44; p=0.016).

Conclusions The high prevalence of HIV, HSV-2 and pregnancy underscore the need for school-based sexual and reproductive health services, and provide further impetus for the inclusion of adolescents in behavioural and biomedical trials with HIV incidence endpoints.