Gonococcal infection, infertility, and population growth: II. The influence of heterogeneity in sexual behaviour.

Heterogeneity in sexual behaviour has an important influence on the transmission dynamics of sexually transmitted diseases (STDs). The authors describe the development of a simple mathematical model, incorporating such heterogeneity, to investigate the demographic impact of gonorrhoea on human population growth in developing countries where the disease is endemic. Earlier predictions, based on a model with homogeneous mixing, are shown to be in good qualitative agreement with the predictions of a more complex mathematical framework in which the population is stratified both by sex and into two subgroups representing low and high sexual activity, defined on the basis of rates of sexual partner change. Analyses also demonstrate that the pattern of mixing (assortative to random) between the sexual activity classes has an important influence on the predicted prevalence of gonococcal infection in a defined community. The more complex model supports earlier conclusions that gonorrhoea, via its impact on fertility, can significantly reduce net population growth rates.