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AIDS. 1997 Jul;11(8):1023-30.

Trends in HIV-1 prevalence may not reflect trends in incidence in mature epidemics: data from the Rakai population-based cohort, Uganda.

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1
Center for Population and Family Health, Columbia University School of Public Health, New York, USA.

Abstract

OBJECTIVES:

To assess whether trends in serial HIV-1 prevalence reflect trend in HIV incidence, and to decompose the effects of HIV-1 incidence, mortality, mobility and compliance on HIV-1 prevalence in a population-based cohort.

DESIGN:

Two-year follow up (1990-1992) of an open cohort of all adults aged 15-59 years, resident in a sample of 31 representative community clusters in rural Rakai District, Uganda.

METHODS:

A detailed household enumeration was concluded at baseline and in each subsequent year. All household residents were listed, and all deaths and in- and out-migrations that occurred in the intersurvey year wee recorded. In each year, all consenting adults were interviewed and provided a serological sample; 2591 adults aged 15-59 years were enrolled at baseline.

RESULTS:

HIV prevalence among adults declined significantly 1990 and 1992 (23.4% at baseline, 21.8% in 1991, 20.9% in 1992; P < 0.05). Declining prevalence was also observed in subgroups, including young adults aged 15-24 years (from 20.6 to 16.2% over 3 years; P < 0.02), women of reproductive age (from 27.1 to 23.5%; P < 0.05), and pregnant women (from 25.4 to 20.0%; not significant), However, HIV incidence did not change significantly among all adults aged 15-59 years (2.1 +/- 0.4 per 100 person-years of observation (PYO) in 1990-1991 and 2.0 +/- 0.3 per 100 PYO in 1991-1992], nor in population subgroups. HIV-related mortality was high (13.5 per 100 PYO among the HIV-positive), removing more infected persons that were added by seroconversion. Net out-migration also removed substantial numbers of HIV-positive individuals.

CONCLUSIONS:

In this mature HIV epidemic, HIV prevalence declined in the presence of stable and incidence. HIV-related mortality contributed most to the prevalence decline. Prevalence was not an adequate surrogate measure of incidence, limiting the utility or serial prevalence measures in assessing the dynamics of the HIV epidemic and in evaluating the impact of current preventive strategies.

PIP:

Findings are reported from a 2-year follow-up study of an open cohort of people aged 15-59 years living in a sample of 31 representative community clusters in rural Rakai district, Uganda, to measure whether trends in serial HIV-1 prevalence reflect trends in HIV incidence, and to gain insight into the effects of HIV-1 incidence, mortality, mobility, and compliance upon HIV-1 prevalence. In each year of study, all consenting adults provided a serological sample and were interviewed; 2591 adults were enrolled at baseline. HIV prevalence among adults declined significantly between 1990 and 1992; from 23.4% in 1990, to 21.8% in 1991, and 20.9% in 1992. Declining prevalence was also observed in subgroups, including young adults aged 15-24 years from 20.6% to 16.2%, reproductive-age women from 27.1% to 23.5%, and pregnant women from 25.4% to 20.0%. The decline in HIV prevalence among pregnant women, however, is not significant. HIV incidence did not change significantly among all adults aged 15-59 years, nor in population subgroups. HIV-related mortality was 13.5/person-year of observation among those who were HIV-positive. Substantial numbers of HIV-infected individuals were also loss to emigration.

[Indexed for MEDLINE]

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