Statistical methods for monitoring the AIDS epidemic

This article describes statistical methods for monitoring the epidemic of the acquired immunodeficiency syndrome (AIDS). A log-linear model is proposed to estimate AIDS incidence and its growth rate while taking account of delays in case reporting. An empirical Bayes approach for estimating the epidemic growth rate in low prevalence subgroups is introduced. These methods are illustrated with an analysis of AIDS incidence trends for seven risk groups in each of six geographic regions using the Centers for Disease Control AIDS case registry data as of September 1987. The analysis finds that AIDS incidence is currently doubling about once every two years and that the relative composition of new cases is shifting away from the older epidemics such as in north-eastern homosexual communities.