Trends in Incidence of Syphilis Among U.S. Adults From January 2017 to October 2024

Syphilis incidence has increased significantly in the U.S., raising concerns about onward transmission. Using near-real-time data, this study examined monthly trends in syphilis incidence among U.S. adults from January 2017 to October 2024, focusing on overall patterns and stratifying by demographic and clinical characteristics.

Monthly syphilis incidence from January 2017 to October 2024 was calculated using Truveta Data - a large, diverse database of electronic health records from U.S. healthcare systems. Poisson regression models were used to assess trends, with adjustments for the early COVID-19 pandemic period.

The analysis included 56,980,788 adults and 21,180 first-time syphilis cases, with a cumulative incidence of 35.9 per 100,000 person-years. Overall, incidence increased from 1.26 per 100,000 person-years in January 2017 to 4.88 in July 2022, then plateaued and declined to 2.47 by October 2024. The decline was larger among populations with a high burden for syphilis infection, including men, younger adults, individuals identifying as American Indian/Alaskan Native or Native Hawaiian/Pacific Islander, those with behaviors associated with sexually transmitted infection acquisition, those using pre-exposure prophylaxis for HIV prevention, and individuals living with HIV. Conversely, incidence rose among populations with lower burdens-those without behaviors associated with sexually transmitted infection acquisition, pre-exposure prophylaxis use use, or living with HIV-implying a shift in the transmission dynamics.

The findings highlight recent declines in syphilis incidence, primarily among high-burden groups, while syphilis incidence is rising in low-burden populations. These findings underscore the need to address factors contributing to syphilis transmission in diverse populations, including those that may not perceive themselves as vulnerable.