Threshold parameters for a simple stochastic partnership model of sexually transmitted diseases formulated as a two-type CMJ process.

A simple stochastic model describing an epidemic of a sexually transmitted disease, accommodating the formation and dissolution of partnerships, was formulated within a two-type Crump-Mode-Jagers (CMJ) process in continuous time. A submodel, describing the formation and dissolution of partnerships, was formulated in terms of a semi-Markov process with a finite state space and death as an absorbing state. This model was then linked to a two-type CMJ process through offspring distributions. Numerical values of threshold parameters greater than one suggests that either the epidemic dies out with a probability significantly different form zero or it spreads explosively in the population.