(P36) TRENDS IN PRIMARY AND SECONDARY SYPHILIS AMONG MEN WHO HAVE SEX WITH MEN DURING THE 2022 U.S. MPOX OUTBREAK

Background:
During the 2022 mpox epidemic, men who have sex with men (MSM) may have changed sexual and healthcare seeking behaviors to prevent spread of infection, potentially impacting transmission of other STIs. We investigated changes in reported primary and secondary (P&S) syphilis cases among MSM during the 2022 U.S. mpox outbreak.

Methods:
We reviewed P&S syphilis case notifications provided to CDC through the National Notifiable Diseases Surveillance System. Restricting to cases among MSM, we compared the number of 2022 cases reported for a given Morbidity and Mortality Weekly Report (MMWR) week to the number of 2021 cases reported in the same week, expressing 2022 cases as a percentage of 2021 cases, and compared 2022 and 2021 cumulative case totals.

Results:
Prior to May 17 (MMWR week 20) when the first 2022 U.S. mpox case was reported, the weekly number of P&S syphilis cases among MSM reported in 2022 as a percentage of the cases in the same week in 2021 was generally higher (average percentage of previous year: 104.0%). During the first four months of the mpox outbreak (MMWR Weeks 21-38; May 22-September 24), weekly P&S syphilis cases in 2022 were substantially higher than 2021 case counts (average percentage of previous year: 110.7%). From MMWR Week 39 (week of September 25) until the end of the year, 2022 case counts were generally lower than 2021 case counts (average percentage of previous year: 96.9%). The 2022 cumulative total of P&S syphilis cases among MSM was 4.0% higher than for 2021.

Conclusion:
Initial increases in weekly P&S syphilis case counts among MSM during the mpox outbreak may reflect changes in healthcare seeking behavior as more men sought lesion-related care leading to increased P&S syphilis diagnoses. Decreases in weekly cases later in 2022 may reflect reduced transmission due to earlier diagnoses and treatment, or sexual behavior changes.