Epidemiologic Characteristics of an Ongoing Syphilis Epidemic Among Men Who Have Sex With Men, San Francisco

Background: Since 2001, San Francisco has experienced a sustained syphilis epidemic that has been nearly exclusively limited to men who have sex with men. We examined the characteristics associated with changes in the syphilis epidemic in San Francisco. Methods: All primary and secondary (P&S) syphilis cases reported to the San Francisco Department of Public Health between 2001 and 2011 were examined using joinpoint analysis to identify periods within the broader epidemic. Characteristics of the index cases were compared across the periods using W 2 statistics and t tests. Results: Three distinct periods were identified, an acute increase, decline, and then period of resurgence. In the most recent period of resurgence, compared with earlier periods, patients with P&S syphilis were more likely to have a prior syphilis infection, were older, were more likely to meet partners online, and were more likely to have a partner from outside San Francisco. Conclusions: In an analysis of 11 years of P&S syphilis data, several factors were associated with declines or resurgences. Innovative prevention measures are needed to reduce syphilis morbidity among men who have sex with men.