An exploratory intersectional analysis of syphilis prevalence among people who inject drugs in Montreal, Canada

ABSTARCTO_ST_ABSBackgroundC_ST_ABSSyphilis notifications have increased among women and heterosexual men in Canada and people who inject drugs (PWID) are an emerging group at risk of infection. We examined syphilis prevalence among PWID and how this varied by intersecting population groups, socio-structural factors and sexual and substance use behaviors. MethodsData were from HEPCO, a cohort study of PWID in Montreal. We tested for syphilis via venipuncture with treponemal testing reflexed to non-treponemal testing if positive. We included the result at each persons first test and exact logistic regression was used to examine differences in the prevalence of lifetime syphilis infection. ResultsBetween November 2022 and March 2024, 386 people (16.1% women) had a syphilis test. Thirty-three people (8.6%) had lifetime syphilis and two people (0.5%) had active syphilis. Prevalence was significantly higher among men identifying as gay or bisexual, men with HIV, and those who reported recent sex work, condom-less sex, 2 or more sex partners and amphetamine injecting. Among women with syphilis, prevalence was higher among those who reported recent sex work, recent unstable housing and amphetamine injecting; however, the confidence interval included the null. ConclusionActive syphilis infection was uncommon among this cohort of PWID; however, lifetime syphilis infection was almost 9%. Among men in this cohort, there is evidence that syphilis intersects with other key population group characteristics. More data are needed to better understand syphilis among women who inject drugs. Periodic syphilis testing among PWID may be justified alongside testing for other sexually transmissible and blood borne infections. What is already known on this topicContemporary increases in syphilis infection notifications in high income countries has been linked to substance use, including injecting drug use. However, there is a limited understanding of syphilis specifically among people who inject drugs. What this study addsThis is the first study in more than 10 years to examine syphilis prevalence among people who inject drugs in Montreal, the second biggest city in Canada. Active syphilis was uncommon but still higher than the Canadian general population. Lifetime syphilis was associated with a range of intersecting key population groups and behaviours. How this study might affect research, practice or policyOur study provides a contemporary understanding of syphilis specifically among people who inject drugs in Montreal. Syphilis testing may be warranted among people who inject drugs to ensure prevalence stays low and guidelines from the Quebec government dating from 2019 should be revised.