Incidence of HIV-1 infection and changes in prevalence of reproductive tract infections and sexual risk behaviours: a population-based longitudinal study in rural Tanzania.

This study aimed at describing the prevalence and incidence of HIV-1 and change in the prevalence of reproductive tract infections (RTIs) and sexual risk behaviours in the rural Kilimanjaro region of Tanzania. Two cross-sectional surveys among the total village population of Oria were conducted in 1991 and 1993. All individuals with a permanent address in the village were registered and invited to participate. After informed consent, participants gave blood for HIV-1 testing. Participants aged 15-44 years were interviewed regarding their socio-demographic characteristics and sexual risk behaviours and underwent genital examination and testing for RTIs. In 1991 and 1993, respectively, 3 239 (83.6%) and 2 191 (76.9%) individuals in the village participated. Prevalence of HIV-1 increased from 1.3% to 1.8%, but the difference was not significant (p = 0.17). HIV-1 incidence was 13.0/1000 person-years-at-risk (PYAR) for women and 4.3/1000 PYAR for men (relative risk was 3.0; 95% CI: 1.12-8.16). There was a significant increase in the prevalence of gonorrhoea, bacterial vaginosis and vaginal candidiasis (p < 0.001). The percentage of individuals who reported having multiple sexual partners during the 12 months preceding the survey increased from 12.9% to 24.1% (p < 0.001). The results suggest that RTIs and HIV-1 infections increased in this population in the early 1990s. Women were at higher risk of HIV-1 infection as compared to men. Sexual risk behaviours and RTIs may have contributed to HIV-1 transmission in this community. The data collected may help to inform the future design and evaluation of various intervention measures.