Homosexual role separation and AIDS epidemics: Insights from elementary models

Simple models of a closed homosexual population are developed to explore the effect of differentiation of roles in anal intercourse on the size of an AIDS epidemic. Preferential and random mixing among the sex‐role subgroups are modeled via a concept of partnership‐formation rates for pairs of individuals. Models of differing mixing assumptions are compared via a concept of reference reproductive rate. Under the assumption of no risk associated with insertive anal intercourse, explicit epidemic thresholds are determined; epidemic intensity increases with increasing size of the dual‐role (insertive and receptive) subpopulation. Other results indicate that there is a threshold for reproductive rates which determines whether or not random mixing yields a more severe epidemic than a form of segregated mixing, and that for fixed epidemiological conditions, a certain level of like‐with‐like preference, rather than random mixing, yields a worst‐case scenario.