Abstract Background Syphilis has reemerged as a global public health concern. In Ontario, Canada’s most populous province, a 340% increase in infectious syphilis cases was observed between 2013-2023. This surge was accompanied by a demographic shift, with women emerging as the fastest-growing at-risk group. We examined intersecting risk factors associated with syphilis seropositivity among a street-involved population. Methods Data was collected from the Syphilis Point of Care Rapid Test and Immediate Treatment Evaluation (SPRITE) study–an outreach model of care implemented by eight public health units (PHUs) across Ontario between 2023-2024. Reactive treponemal antibodies defined syphilis seroprevalence. A mixed-effects regression with a log-binomial distribution was used to evaluate the association between risk factors and seropositivity. Adjusted prevalence ratio (aPR) controlled for age and sex and clustering by PHUs. Results A total of 630 participants; 42% women, median age of 38, were included. 19.1% of participants reported having sexual risk factors, using illicit drugs, and being un(der)housed. Overall, syphilis seroprevalence was 7.6% (95% CI 5.5,9.7), with significant heterogeneity across the province and higher among those reporting three risk factors (19.2% (11.2, 29.7) compared to one risk factor (4.8% (1.8,10.1). Seropositivity was higher among women (aPR 1.62 (0.94,2.80)) and people who use illicit drugs (aPR 2.30 (0.93,5.50)), particularly those who use crystal methamphetamine (aPR 2.88 (1.31,6.33)). Conclusion Syphilis is heightened at the intersection of sexual risk factors, illicit drug use, and housing instability among equity-deserving populations. Targeted outreach models of care are necessary to reach this emerging at-risk population.
Mackrell et al. (Thu,) studied this question.