Abstract:
The main objective of this study was to improve the methodological basis for
modeling the HIV/AIDS epidemics in adults in sub-Saharan and to develop
estimates of prevalence, incidence and mortality and to study the impact of
HIV/AIDS on life expectancy and population growth with examples of Zimbabwe,
Tanzania and Sudan. Understanding the magnitude and trajectory of the HIV/AIDS
epidemic is essential for planning and evaluating control strategies.
Previous mathematical models were developed to estimate epidemic trends
based on sentinel surveillance data from pregnant women. In this study, we have
extended these models in order to take full advantage of the available data. The
methodology involved a Gauss Newton approach for the estimation of prevalence
and incidence of HIV/AIDS in the studied countries using curve fitting procedure.
Further back calculation method was used to estimate AIDS cases and mortality.
Also life tables were constructed to asses the impact of HIV/AIDS on life
expectancy. To trace the impact of HIV/AIDS on population growth, we have
projected the population growth with and without AIDS using demographic
techniques for estimating population growth.
For every country three models were estimated and the best among them
were selected for Zimbabwe, double logistic curve has been selected. The same
model was found to be suitable for Tanzania. For Sudan, we used the rational model
because it produced suitable fitting of the data. Also the estimated models were
compared with the UNAIDS estimate.
Our application to the model revealed the impact of HIV/AIDS in the target
countries where adult HIV prevalence is significant. The epidemic has already
had a number of serious consequences, including rise in the number of deaths and
the reduction of life expectancy and the, particularly deaths of persons aged 15
to 49. Furthermore, some of the serious effects of the epidemic are expected to
worsen in the future. By the year 2020 population of studied countries is
expected to be lower than it would have been in the absence of AIDS. Increases of
mortality have been particularly marked in the Zimbabwe the country with the
highest
HIV prevalence. Also life expectancy at birth has already fallen
dramatically, dropping within a decade or two to levels last recorded before
1985, and in the cases of Tanzania, the impact of HIV/AIDS on mortality and
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population growth is of less degree than in Zimbabwe, this due to the fact that
Tanzania epidemic is considered as moderate. For Sudan the impact of HIV/AIDS is
less effective, because the epidemic is of low level.
The study recommends the development of ANC data since it is the only
available source and to use different stochastic epidemiological curves for fitting
data, and finally to validate the HIV/AIDS impact by other independent studies.
