Historical and Current Trends in the Epidemiology of Early Syphilis in San Francisco, 1955 to 2016.

backgroundSeventeen years into a sustained epidemic, early syphilis (ES) rates in San Francisco (SF) are continuing to increase and the demographics of the affected population are changing. We provide a historical overview of ES in SF among men who have sex with men (MSM) and describe trends in the epidemiology and disease investigation outcomes.

methodsWe examined data from the SF Department of Public Health's patient-based registry of integrated STD surveillance, clinical, and field investigation data to describe demographic and behavioral characteristics of ES cases, as well as outcomes of syphilis partner services (PS). χ Tests were performed to examine categorical differences across periods. Analysis of variance was used to examine differences in continuous variables.

resultsIn 2016, 1095 ES cases were reported among males in SF, a 219% increase from the 343 cases identified 10 years ago. Between 1996-1999 and 2010-2016, an increasing proportion of ES cases were among MSM younger than 25 years, nonwhite, and HIV negative (P < 0.05). A decreasing proportion of ES cases were assigned for PS, among whom a smaller proportion of reported sex partners were identified by name, resulting in an overall decline in the proportion of cases who had at least one named partner treated as a result of PS (Disease Intervention Rate) from 30.5 in 2000-2004 to 14.8 in 2010-2016.

conclusionsSyphilis case rates continue to increase in SF and the epidemic is expanding beyond a core population. Additional resources and innovative prevention approaches are needed to reduce the burden of syphilis among MSM.