Early Latent Syphilis - Barometer of Syphilis Control Program

Background: During 2007 in the United States, 22,234 cases of infectious syphilis (infections of one year or less duration) were reported. Of these cases 14% were reported in the primary stage, 37.5% in secondary and 48.4 in early latent stage of the disease

Objectives: Build a simulation model for the transmission of infectious syphilis. Use this model to evaluate intervention strategies instituted in different stages of syphilis

Methods: We built a simulation model based on syphilis transmission dynamics. In this model susceptible persons after acquiring syphilis infection (with a certain probability), through sexual contact with an infectious individual, enter the incubating period of disease. These patients then enter into primary stage, and after certain period move to secondary stage and then to early latent stage of the disease. It is assumed that time spent in different stages of syphilis follow gamma distribution, with an average time of 6 weeks in primary and 3 months in secondary stage. It is also assumed that during this period population remains constant and a patient, on the average, has one new sex partner per month. The probability of transmitting infection to a susceptible partner varies from stage to stage with highest in primary and least (0) in latent stage.

Results: Results indicate that interventions in the early latent stage of disease do not reduce transmission of infectious syphilis. Interventions instituted in primary stage reduce more infections as compared to interventions in secondary stage

Conclusions: To control infectious syphilis, interventions should be instituted in the primary and early part of secondary stage of disease. Strategies should be planned to bring infected persons to treatment as soon as possible.

Implications for Programs, Policy, and/or Research: We provide a quantitative approach to compare different syphilis control strategies. Policy makers, using this approach can formulate optimum control strategies.