Two core group models for sexual transmission of disease

Abstract

Models for sexually transmitted disease generally assume that the influence of all individuals is identical in the spread of disease during the period of infection. In this paper, two disease transmission models, which depend on the core group (the group of individuals who are sexually very active) are examined. In the first model, the core group is a subpopulation of susceptibles and in the second model, the core group is a subpopulation of infectives. It is assumed that each core individual comes into sexual contact with an average number of other individuals per unit time. For each model the threshold conditions for an endemic infection are determined. The stability at the uninfected state and the prevalence at the infected state are investigated. The results show that the transmission dynamics of epidemic disease is critically dependent on the effects of small subpopulations with varying levels of sexual activity. Therefore, the average number of sexual encounters of the core group can play an important role in the spread of disease.