Multiregion contact systems for modelling STD epidemics.

This paper elicits properties of some multiregional contact systems for STD infections that are intended to assist the understanding of disease control strategies. To this end, a space-time SIS model is described that maintains the symmetry of contact that is inherent in the formation of sexual partnerships. It is demonstrated how the characteristic stability conditions of this model provide a framework for understanding the potential for sustained transmission after the introduction of the agent into a given region. Then, more complex SI specifications are derived that are particularly relevant to the transmission of HIV. These extensions include the introduction of alternative modes of travel and behavioural adaptations made in response to the circulation of HIV and the incidence of AIDS. The discussion suggests some additions to the systems that might enhance their applicability in practice. Copyright 2000 John Wiley & Sons, Ltd.