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South African Journal of Science

versión On-line ISSN 1996-7489
versión impresa ISSN 0038-2353

S. Afr. j. sci. vol.103 no.3-4 Pretoria mar./abr. 2007




An investigation into the extent of uncertainty surrounding estimates of the impact of HIV/AIDS in South Africa



Leigh F. JohnsonI; Rob E. DorringtonI; Alan P. MatthewsII

ICentre for Actuarial Research, University of Cape Town, Private Bag, Rondebosch 7701, South Africa
IISchool of Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000




HIV/AIDS statistics have been the source of much controversy in South Africa, but often the extent of uncertainty around these estimates is ignored. There is need for an assessment of the range of uncertainty around often-quoted HIV/AIDS statistics. This analysis determines ranges of uncertainty around the inputs and outputs of the ASSA2002 AIDS and Demographic model of the South African HIV/AIDS epidemic, using a generalized likelihood uncertainty estimation approach. A sample of 500 parameter combinations was drawn by weighting randomly generated parameter combinations by likelihood functions defined on the basis of four South African HIV/AIDS data sets. The estimated number of HIV infections in mid-2005 was 5.1 million (95% prediction interval: 4.2-6.0 million), equivalent to an HIV prevalence rate of 11.1% (9.1-13.1%). Between mid-2004 and mid-2005, the estimated number of new HIV infections was 490 000 (370 000-590 000) and the estimated number of AIDS deaths was 320 000 (270 000-380 000). The posterior mean HIV survival time was estimated to be 11.5 years (95% credibility interval: 10.0-12.9 years), longer than estimated for elsewhere in the developing world. This analysis confirms that South Africa is experiencing a severe HIV/AIDS epidemic, and suggests that HIV/AIDS epidemiology in the country probably differs from that elsewhere in Africa.



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