Modeling the Impact of HIV-AIDS Epidemic on Mortality in Sub-Saharan Africa: with Reference to Zimbabwe, Tanzania and Sudan (1985 – 2003)

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 xvi 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.