Mathematical Modeling of Epidemic Syphilis Transmission: Implications for Syphilis Control Programs

Background and Objectives: The past 10 years' wave of syphilis epidemics has challenged syphilis control programs. Although apparently connected to drugs-for-sex trading of crack cocaine, the genesis and resolution of these epidemics is poorly understood. Goals of the Study: The goals of this study were to develop a mathematical model of epidemic syphilis transmission based on empiric data, to stimulate and ascertain behavioral and sociologic features necessary to produce epidemic transmission, and to explore mechanisms leading to resolution of epidemic transmission. Study Design: The study used multi-compartment iterative computer simulation using empirically derived input data. Results: Epidemic transmission resulted from adding a small core group of individuals with very high levels of partner exchange (300-400 partners per year) to a population with levels of partner exchange seen in the general population. Epidemic resolution could result from immunity or subtle changes in the size or partner exchange rate of the core group. Conclusions: There is a need for sexually transmitted disease control programs to reevaluate their approach to prevention and control of epidemic syphilis in light of data on transmission dynamics.