High potential of escalating HIV transmission in a low prevalence setting in rural Tanzania

Previous surveillance among antenatal clinic (ANC) attendees within the remote rural Manyara and Singida regions in Tanzania identified an imminent but still, relatively low HIV epidemic. We conducted a population-based HIV study to identify risk factors and validate the representativeness of ANC-based estimates.

Using a two-stage cluster sampling approach, we enrolled and then interviewed and collected saliva samples from 1,698 adults aged 15-49 years between December 2003 and May 2004. We anonymously tested saliva samples for IgG antibodies against HIV using Bionor HIV-1&2 assays (R). Risk factors for HIV infection were analysed by multivariate logistic regression using the rural population of the two regions as a standard.

The prevalence of HIV in the general population was 1.8% (95% CI: 1.1-2.4), closely matching the ANC-based estimate (2.0%, 95% CI: 1.3-3.0). The female to male prevalence ratio was 0.8 (95% CI 0.4-1.7). HIV was associated with being a resident in a fishing community, and having recently moved into the area. Multiple sexual partners increased likelihood of HIV infection by 4.2 times (95% CI; 1.2-15.4) for men. In women, use of contraceptives other than condoms was associated with HIV infection (OR 6.5, 95% CI; 1.7-25.5), while most of the population (78%) have never used condoms.

The HIV prevalence from the general population was comparable to that of pregnant women attending antenatal clinics. The revealed patterns of sexual risk behaviours, for example, close to 50% of men having multiple partners and 78% of the population have never used a condom; it is likely that HIV infection will rapidly escalate. Immediate and effective preventive efforts that consider the socio-cultural contexts are necessary to reduce the spread of the infection.