Objective: To determine the incidence of infection with HIV-1 and the risk factors associated with seroconversion in three geographical strata of a rural Ugandan district.
Design: Serological, sociodemographic, and behavioural surveys of everyone aged 13 or more in 21 randomly selected communities at baseline and one year later.
Setting: Rural population of Rakai district, southwestern Uganda, residing in main road trading centres, secondary trading villages, and agricultural villages.
Subjects: In 1989, 1292 adults provided a blood sample and interview data; one year later, 778 survivors (77%) who had been seronegative at baseline provided follow up data.
Main outcome measures: Incidence of HIV infection in relation to individual characteristics and risk factors, including place of residence.
Results: Incidence of HIV infection in all adults was 2.1/100 person years of observation (SE 0.5 (95% confidence interval 1.1 to 3.1)); in people aged 15-39 the incidence was 3.2/100 person years. Incidence was highest in men and women aged 20-24 (9.2/100 person years (3.9) and 6.8/100 person years (2.9) respectively). Risk factors significantly associated with seroconversion were age 24 and under and two or more sexual partners. Between the surveys the proportion of all respondents reporting high risk behaviour (two or more partners) significantly increased from 8.9% to 12.3%.
Conclusions: Despite preventive programmes and substantial knowledge about AIDS the incidence of HIV infection remains high in this rural population. Prevention aimed at vulnerable rural communities is urgently needed to contain the HIV epidemic.
PIP: In 1990, researchers followed up on as many of the 1292 adults they surveyed in 1989 as they who lived in rural Rakai district in southwestern Uganda to determine HIV-1 incidence and the risk factors associated with seroconversion. They were only able to follow up on 774 of the 1037 adults who were HIV-1 seronegative in 1989. In 1989, knowledge about AIDS and about sexual intercourse as a mode of HIV transmission was high (94% and 86%, respectively). The 1989 HIV-1 seroprevalence rate ranged from 38.5% in trading centers to 8.6% in agricultural villages off main and secondary roads. 21 (2.7%) had seroconverted (incidence = 2.1/100 person years). Since the researchers oversampled in trading centers, they estimated the weighted seroincidence to be 1.9%. HIV-1 seroconversion peaked in the 20-24 year old age group with it being greater in men than in women (9.2% vs. 6.8%). The most significant risk factor for seroconversion was number of sexual partners (8.3% for 2 or more partners vs. 2.5% for 0-1 partners; rate ratio = 3.4; p .01 for trend). The risk of seroconversion for someone with just 1 sexual partner was high (2.8%), reflecting the high HIV-1 seroprevalence in Rakai district. The percentage of subjects with at least 2 sexual partners rose from 8.9% in 1989 to 12.3% in 1990. Seroconversion was not associated with injections. No one had had a blood transfusion. Attendance at a 1989 AIDS education rally did not affect HIV seroconversion. In fact, it was greater among people attending the rally (3.5% vs. 2.1%). Logistic regression revealed that age and numbers of partners were the only significant factors affecting seroconversion (odds ration [OR] for 15-24 years compared to 25-39 years was 3.9 and OR for 2 or more sexual partners was 6.5). These findings indicated that existing HIV/AIDS education programs do not reduce HIV transmission and that better strategies are needed.