AIDS: predicting cases nationally and locally.

Models for predicting the future course of the AIDS epidemic can be divided into five types: trend extrapolation models, compartment models, models based on the incubation period, comparison models, and models produced by expert committees. To predict the numbers of cases of AIDS in the United Kingdom and in East Anglia and Cambridge a two stage approach was chosen using trend extrapolation for the national case reports followed by reduction in scale to the two localities. The method predicted that about 2700 cases would be reported nationally during 1990 and about 6000 during 1992. The number of people with AIDS expected to present for treatment in East Anglia during 1990 was 48, and during 1992 was 105; for Cambridge the corresponding figures were 20 and 43. These figures with their estimated 95% confidence intervals will be used for planning local services for people with AIDS, and they emphasise the need for preventive action.