Modelling an epidemic
Modelling of the HIV and AIDS epidemic in South Africa by actuaries began with the Metropolitan model, developed by Peter Doyle and Donald Miller in 1989. As this model was proprietary the Actuarial Society of South Africa (ASSA) felt that it was necessary for the general public to have access to a model that users could alter to suit their needs. In 1996 the AIDS Committee of ASSA released their first AIDS and Demographic model, namely ASSA500, a simplified and more user friendly version of the Metropolitan model. The model was primarily designed to make the users more aware of the impact of AIDS on mortality, and only modelled a hypothetical population. The ASSA600 model was designed to model the impact on the country as a whole and was released in early 1999. Since the release of the subsequent ASSA2000 model, the name of the model has referred to the year of the latest antenatal clinic and mortality data that were used to calibrate the model (calibration is the process of adjusting the model to reflect reality as closely as possible).
The ASSA2002 suite of models that was released in 2004 included significant changes and various improvements. For the first time in South Africa the impact of five HIV and AIDS prevention and treatment programmes were modelled. The model allowed the user to assess the impact of HIV related information and education, improved treatment of sexually transmitted diseases, voluntary counselling and testing, prevention of mother-to-child-transmission and antiretroviral treatment.
The ASSA2003 model that followed soon after ASSA2002 extended the model to each of the nine provinces in South Africa. This allowed users to assess the differential impact of AIDS in the different provinces, as well as differences between provinces in the extent of antiretroviral treatment rollout.