Syphilis in heterosexual women: case characteristics and risk factors for recent syphilis infection in Tokyo, Japan, 2017–2018

This is the authors' abstract. We don't add key points for this paper.

In response to an increase in heterosexual syphilis notifications in Tokyo, we conducted a questionnaire-based case-control study among women aged ≥20 years and sexually active in the past six months who sought a syphilis test in Tokyo during 2017-2018. Cases were women diagnosed as recent syphilis infection based on serological tests. Controls were serologically non-reactive or those with only a past syphilis infection. We described cases and assessed for risk factors of recent syphilis using logistic regression. A total of 524 women (60 cases, 464 controls) were enrolled. Notably, among cases, 10 (16.7%) were students, 3 (5.0%) had a history of syphilis, and 14 (23.3%) had a single sex partner in the past six months. Female sex worker (FSW) status was strongly associated with syphilis (odds ratio [OR] = 3.40; 95% confidence interval [CI] = 1.96-5.90). In multivariable analysis, recent syphilis was associated with inconsistent condom use for vaginal/anal sex among FSWs (adjusted OR [aOR] = 3.42; 95%CI = 0.92-12.70) and among non-FSWs, with younger age (aOR = 0.36; 95%CI = 0.19-0.70; increase per category from 20-24, 25-29 to ≥30 years) and ≤high school education (aOR = 5.24; 95%CI = 1.95-14.10). A notable proportion of cases were those with first time infection and those with only a single partner. Moreover, risk factors differed between FSWs and non-FSWs, and a multi-pronged approach to prevent syphilis is required.