Disparities in Syphilis Trends and the Impact of the COVID-19 Pandemic: A Joinpoint Analysis of Florida Surveillance Data (2013-2022)

Introduction: Syphilis, a sexually transmitted infection caused by the bacterium ​​​​​​Treponema pallidum, has reemerged at an increasing rate globally in recent years, posing a significant public health concern. Visualizing and analyzing time series trends of syphilis across various demographics and geographic regions, and how syphilis trends varied during the pandemic coronavirus disease 2019 (COVID-19), would help public health policymakers develop targeted strategies and interventions to effectively address the rising rates of syphilis, ultimately improving overall public health outcomes.

Methods: A retrospective study was conducted using surveillance data on infectious syphilis cases reported to the Florida Department of Health, between 2013 and 2022. Age-standardized syphilis rates (ASSRs) per 100,000 persons were calculated using the 2000 U.S. standard population data. The average annual percentage change (AAPC) in the ASSRs was analyzed according to age, gender, race, geographic locations, and the COVID-19 pandemic period to quantify the epidemiological syphilis trends using joinpoint regression models.

Results: In Florida, the ASSR significantly increased from 8.65/100,000 in 2013 to 23.08/100,000 in 2022 across different demographic groups, with an overall AAPC of 11.47 (95% confidence interval (CI): 9.85-13.43). This increase in the AAPC was more pronounced in females (AAPC = 20.97; 95% CI, 18.61-24.49) than in males (AAPC = 10.34; 95% CI, 8.19-12.98). The increasing trends of infectious syphilis were observed across all age groups, with greater increases among those aged 25-49 years (AAPC = 12.32; 95% CI, 10.09-15.18), aged 50-69 years (AAPC = 13.42; 95% CI, 9.41-18.89), and aged over 70 years (AAPC = 13.63; 95% CI, 9.23-21.95), compared to those aged less than 24 years (AAPC = 7.86; 95% CI, 7.06-8.81). The increasing trends were comparable across racial groups, with an AAPC of 8.08 (95% CI, 5.47-11.15) for Hispanics, 11.84 (95% CI, 10.02-14.09) for non-Hispanic Whites, 10.49 (95% CI, 8.75-12.66) for non-Hispanic Blacks, and 11.29 (95% CI, 5.28-19.57) for non-Hispanic individuals of other races, respectively. The AAPC for the COVID-19 pandemic period was 12.99 (95% CI, 8.48-16.21), which was comparable to the pre-pandemic period (AAPC = 11.58; 95% CI, 10.17-12.76), indicating that this upward trend in infectious syphilis persisted throughout the COVID-19 pandemic. At the county level, over the 10-year period, the average ASSRs ranged from 0.89/100,000 in 2013 to 25.41/100,000 in 2022, with the estimated AAPCs varied from 2.47 (95% CI, -1.89 to 6.92) in Monroe County to 50.01 (95% CI, 37.71-62.27) in Okaloosa County.

Conclusions: The trend of infectious syphilis increases substantially from 2013 to 2022, with notable differences observed among age, gender, and geographic regions in Florida. Females experienced a greater rise in infectious syphilis cases compared to males. This upward trend in infectious syphilis persisted throughout the COVID-19 pandemic. Efforts are needed to implement strategies to address the rising syphilis rates within high-incidence groups and communities across the state.