Elsevier

The Lancet

Volume 360, Issue 9326, 6 July 2002, Pages 41-46
The Lancet

Articles
Declining HIV-1 incidence and associated prevalence over 10 years in a rural population in south-west Uganda: a cohort study

https://doi.org/10.1016/S0140-6736(02)09331-5Get rights and content

Summary

Background

In Uganda, there have been encouraging reports of reductions in HIV-1 prevalence but not in incidence, which is the most reliable measure of epidemic trends. We describe HIV-1 incidence and prevalence trends in a rural population-based cohort between 1989 and 1999.

Methods

We surveyed the adult population of 15 neighbouring villages for HIV-1 infection using annual censuses, questionnaires, and serological surveys. We report crude annual incidence rates by calendar year and prevalence by survey round.

Findings

6566 HIV-1 seronegative adults were bled two or more times between January, 1990, and December, 1999, contributing 31 984 person years at risk (PYAR) and 190 seroconversions. HIV-1 incidence fell from 8·0 to 5·2 per 1000 PYAR between 1990 and 1999 (p=0·002, X2 for trend). Significant sex-specific and age-group-specific reductions in incidence were evident. Incidence was 37% lower for 1995–99 than for 1990–94 (p=0·002, t-test). On average, 4642 adult residents had a definite HIV-1 serostatus at each yearly survey round. HIV-1 prevalence fell significantly between the first and tenth annual survey rounds (p=0·03, X2 for trend), especially among men aged 20–24 years (6·5% to 2·2%) and 25–29 years (15·2% to 10·9%) and women aged 13–19 years (2·8% to 0·9%) and 20–24 years (19·3% to 10·1%) (all p<0·001, X2 for trend).

Interpretation

Our findings of a significant drop in adult HIV-1 incidence in rural Ugandans give hope to AIDS control programmes elsewhere in sub-Saharan Africa where rates of HIV-1 infection remain high.

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.

Section snippets

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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