ArticlesDeclining HIV-1 incidence and associated prevalence over 10 years in a rural population in south-west Uganda: a cohort study
Introduction
As the HIV/AIDS epidemic starts its third decade, the spread continues at a frightening pace in sub-Saharan Africa. In southern Africa, for example, where presence of a severe epidemic has only lately been officially recognised, evidence points to a fast expanding epidemic.1, 2 Uganda, one of the countries in Africa where the epidemic was first reported, has noted encouraging downward trends in HIV-1 prevalence in rural and urban populations since the late 1990s, from about 28% to 8%.3, 4, 5, 6, 7 Similar reductions or stabilisation in HIV-1 prevalence have been described in Senegal8 and Zambia,9 and for particular groups in Democratic Republic of Congo10, 11 and Kenya.12 These reductions have been attributed in part to successful intensive behaviour change campaigns, such as reduction in number of sexual partners and encouragement of use of condoms.3, 6, 7, 8, 9, 10, 11, 12, 13, 14
Reductions in HIV-1 prevalence, especially those in young adults, probably indicate concomitant falls in HIV-1 incidence. However, other factors, such as mortality rates, migration, and survey coverage,4, 15, 16 also contribute to prevalence trends. Thus incidence trends cannot be estimated directly from prevalence trends. Reductions in HIV-1 incidence trends would provide the most convincing evidence of a decrease in epidemic size, but large, long-term, longitudinal studies are needed to obtain such evidence. We describe the direction of the AIDS epidemic by analysing rates and trends in incidence and prevalence among a population-based cohort located in rural southwest Uganda who were followed up between 1989 and 1999.
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Survey methods
The study population has been described previously,3, 5, 17 but in brief it consisted of all adults (aged 13 years and above) who were resident in a cluster of 15 neighbouring villages in rural southwest Uganda. This open cohort had been under epidemiological surveillance for HIV-1 infection by the Medical Research Council Programme on AIDS in Uganda (MRC), who had used annual censuses, questionnaires, and serological surveys since 1989.
Survey rounds began in November and ended in October
Results
A total of 5238 women and 4589 men were censused and bled between January, 1990, and December, 1999. Of these, 463 women and 283 men were positive for HIV-1 on their first sample and were excluded from incidence analysis. Of the remaining 9081 HIV-1 seronegative adults, 3408 women and 3158 men were bled two or more times. 97 women and 93 men seroconverted in 31 984 PYAR. The median age at seroconversion was 27·0 years (IQR 21·1–37·7) and was lower for women (23·2 years) than for men (29·8
Discussion
We have shown a significant reduction in HIV-1 incidence in a rural adult general population in sub-Saharan Africa. The incidence fell significantly throughout the 1990s in all population groups: men, women, young adults, and older adults. We also noted significant reductions in HIV-1 prevalence in young adults (13–24 years), as shown in our previous reports.3, 17 Our findings are also consistent with previous reports from Uganda of a 40% reduction in HIV-1 seroprevalence in women attending
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