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 12 588.2 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 <greater than or equal to 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.