High prevalence of syphilis in women, minors and precarious patients: a cross-sectional study in a Reunion Island sexually transmitted infection clinic, 2017-2020.

BACKGROUND: Syphilis is a sexually transmitted infection (STI) with a global prevalence estimated at 0.5% in 2012. Syphilis has been on the rise among men who have sex with men (MSM) in high-income countries and remains at endemic levels in low- and middle-income countries. This trend, however, has not been observed in Reunion Island. OBJECTIVES: To determine the prevalence, clinical characteristics and risk factors of syphilis in at-risk patients visiting the South Reunion STI clinic in Reunion Island. METHODS: This monocentric cross-sectional study included all patients who visited our STI clinic between 2017 and 2020. Syphilis serology was performed on all included patients, and data were collected using a standardized self-administered questionnaire. RESULTS: Over the 3-year study period, 2593 patients were enrolled. The prevalence of syphilis was 7.52% (n = 195, 95% CI, 6.50-8.65%) in the overall study population, 11.76% (n = 18, 95% CI, 6.97-18.59%) in minors (aged under 18 years) and 36.36% (n = 16, 95% CI, 21-59%) in pregnant women. The risk factors identified in multivariate analysis were being female [adjusted Prevalence Ratio (aPR) 1.85, 95% CI, 1.10-3.11], being MSM (aPR 2.87, 95% CI, 1.71-4.80), being aged under 18 years (aPR 3.54, 95% CI, 1.90-6.57), living in precarious conditions [aPR 3.12, 95% CI, 2.11-4.62] and being born in Reunion Island (aPR 2.43, 95% CI, 1.42-4.13). The clinical presentation was heterogeneous (plaques and papules, chancre, atypical ulcerations, multiple ulcerations, condyloma lata, etc.). CONCLUSIONS: These findings suggest a high prevalence of syphilis in at-risk patients visiting our STI clinic. Unlike the situation in other high-income countries, the people most at risk of syphilis in Reunion Island are local-born residents, minors, women and precarious patients. This is a source of concern, especially given the risk of resurgence of congenital syphilis on the island.