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

BACKGROUND: Seventeen 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.

METHODS: We 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.

RESULTS: In 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.

CONCLUSIONS: Syphilis 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.