Prevalence of HIV-1 infection in the Kagera region of Tanzania: a population-based study.

A population-based survey was carried out in the Kagera region of the United Republic of Tanzania in 1987 to determine the magnitude of HIV-1 infection and to study associated risk factors. The region was divided into one urban and three rural zones. A multistage cluster sampling technique was adopted. Antibodies to HIV-1 were determined by enzyme-linked immunosorbent assay and confirmed by Western blot analysis. A total of 2,475 adults (aged 15-54 years) and 1,961 children (aged 0-14 years) was studied. The overall prevalence of HIV-1 infection among adults was 9.6%, with a higher prevalence in the urban zone (24.2%) than in the three rural zones (10.0, 4.5 and 0.4%, respectively). The corresponding figures for children were 1.3% overall: 3.9% in the urban area and for the rural areas 1.2, 0.8 and 0.0%, respectively. The age-specific seroprevalence for adults was highest in the age group 25-34 years. The age-standardized sex-specific prevalence was higher among women than men in the urban zone, while it was the same in the rural zones. Change of sexual partners among adults was associated with an increased risk of HIV-1 seropositivity. Travelling outside the region but within the country was also found to be associated with increased risk of HIV-1 infection but only in the rural population.