A transmission model for AIDS.

Mathematical and computer-simulation models of sexually transmitted diseases, which have been used to study gonorrhoea and human papilloma virus transmissions, are applied to the study of AIDS. The problems of adapting the general model to the new problem, within already established principles, are described; and solutions offered. The objective is to predict equilibrium levels for the prevalence and incidence of HTLV-III infection in the U.K. Within the uncertainties of the available information on sexual behaviour in our society, on the risk of transmission and on the natural history of the infection, the model predicts: the infection will be self-sustaining in the heterosexual as in the homosexual population, the equilibrium prevalence of HTLV-III infection may attain 500-800 per 1000 among promiscuous male homosexuals and female prostitutes: 1 to 5 per 1000 among non-promiscuous heterosexual males and females: and 8 to 15 per 1000 overall, these equilibria will be reached in about 10 years among the promiscuous classes, but not for 40 years among the less promiscuous, this implies 20,000 to 40,000 deaths from AIDS per year in the U.K., these estimates will be modified by behaviour changes in the population as a whole, responding to fear of infection and to health-education approaches, but substantial control will depend upon the production of a vaccine and its preferential use in the promiscuous classes.