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Transmitting through time: monitoring HIV transmission rates in rural Tanzania

Monitoring and understanding HIV infection rates over a period of time requires detailed data, not restricted to any one social group. Such detailed data is only available for a few developing country populations. This study focuses on a rural population in the Mwanza region of Tanzania, during the period between 1994 and 2000. Results suggest that the district HIV prevention programme has had little impact on sexual behaviour.

Researchers from the National Institute for Medical Research in Tanzania examined the evolution over time of HIV prevalence and infection rate, in conjunction with any changes in demographics, HIV awareness and sexual behaviour. In order to examine differences in HIV prevalence by place of residence, a distinction was made between three categories of location - the trading centre, peri-trading centre and rural villages.

The research team established a demographic surveillance system in 1994, and thirteen follow-up rounds were conducted during 1994-2000. All adults who were resident in the study area at the last demographic round were eligible for inclusion in the study. Three detailed surveys were conducted, in 1994-5, 1996-7 and 1999-2000.

The principal findings of the study were:

In all survey rounds more women had HIV than men.
For both men and women, HIV prevalence in the last survey was 1.4 times higher than five years earlier. The incidence of HIV during the second half of the study was also significantly higher for both women and men.
Transmission rates were higher in the trading centre than in the nearby rural villages, but the difference became less over time.
Nearly all respondents know about the sexual transmission of HIV and there was a gradual increase in the number who knew that a 'healthy' person could have HIV.
Only a quarter of men and women felt at risk of contracting HIV.
No significant change took place in sexual risk behaviour – including median age of first sexual intercourse, reported number of partners and condom use in high-risk partnerships - during the study period. A small increase was reported (up to 24%) in lifetime condom use among men.

During the study period, the population of Kisesa ward was exposed to the district HIV prevention programme, but no change in sexual behaviour was observed. This lack of change is consistent with trends in Tanzania as a whole.

The low cost HIV-AIDS intervention package is not proving adequate to turn the tide of the epidemic. More intensive AIDS control measures are needed. Long-term observational studies can provide valuable data which complements that obtained through surveillance of pregnant women or high risk groups. This information is important for tracking HIV prevalence and monitoring behaviour change in both high risk groups and the general population.

Source(s):
‘Trends in HIV and sexual behaviour in a longitudinal study in a rural population in Tanzania, 1994-2000’ AIDS 17(18), by G. Mwaluko et al, 2003
'Declining HIV-1 incidence and associated prevalence over 10 years in a rural population in south-west Uganda: a cohort study', The Lancet 360: 41-46, by S.M. Mbulaiteye, et al, 2002
'Changes in male sexual behaviour in response to the AIDS epidemic: evidence from a cohort study in urban Tanzania', AIDS: 10(12):1415-1420, by J.Z. Ng'weshemi et al, 1996

Funded by: Minister of Development Cooperation, the Netherlands

id21 Research Highlight: 28 April 2004

Further Information:
Ties Boerma
Department of Measurement and Health Information Systems
World Health Organisation
1211 Geneva
Switzerland

Contact the contributor: boermat@who.int

National Institute for Medical Research, Tanzania

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