Effects of screening and partner notification on Chlamydia positivity in the United States: a modeling study.

Model structure We describe the model structure and assumptions, for more background information we refer the reader to earlier publications about our modeling approach (1-4). For modeling chlamydia transmission dynamics, a simulation model was used that describes pairformation and -dissolution as well as transmission of infection as stochastic processes. The model describes a heterosexual population of 15 to 64 years. Individuals are characterized by age, sex, sexual activity (high/low), status of infection (not infected, symptomatic infection, asymptomatic infection), time since infection, number and identities of partners. A distinction was made between steady and casual relationships regarding the duration of the relationship and the frequency of sexual contacts during the relationship. In the younger age groups (15-34 years), a subset of the population is defined as the “core group” with higher numbers of partners. In the simulations reported here, the transmission probability of chlamydia infection is assumed to be equal between males and females. The recovery rate differs between the two sexes and depends on whether the infection is symptomatic or not.