Incidence of HIV-1 Infection in Adults and Socio-demographic Characteristics of Seroconverters in a Rural Population in Uganda: 1990-1994

Background: To evaluate HIV-1 incidence among adults and socio-demographic risk factors in a rural population in Uganda, a prospective cohort study was carried out.

Methods: All consenting adult residents in a cluster of 15 neighbouring villages of the Masaka District of south-west Uganda have been participating in annual socio-demographic and serological surveys since November 1989. Those who had a negative serostatus when they were first tested and had at least one serostatus assessment during the 4 years of follow-up (1990-1994) have been evaluated for HIV-1 seroconversion. Incidence rates have been calculated per 1000 person-years of observation and socio-demographic characteristics assessed for association with recent seroconversion.

Results: At the baseline survey, of 4175 adults with assessable serostatus (79% of all censused adults), 342 (8.2%) were seropositive. During 12588.2 person-years of follow-up 89 seroconversions were identified corresponding to an incidence rate of 7.1 (95% CI: 5.6-8.5). Overall rates were highest in females aged 20-24 years (15.2) and in males aged 20-44 years (11.6). There was a significant interaction between age and sex; the ratio of the rate in females to that in males decreased from 3.3:1 to 0.5:1 with increasing age. Rates for males aged > or = 20 years were four times higher than those for younger males. Other significant socio-demographic correlates with risk included not belonging to the majority tribe, non-Muslim religion and length of stay on compound of less than 10 years. Incidence rates did not show any clear trends with time.

Conclusion: These findings further emphasize the need for targeted interventions.