Rising syphilis rates in Canada, 2011-2020.

Background: Syphilis rates are of public health concern in Canada, with multiple jurisdictions reporting outbreaks over the past five years. The objective of this article is to describe trends in infectious and congenital syphilis in Canada 2011-2020.

Methods: Routine surveillance of syphilis is conducted through the Canadian Notifiable Disease Surveillance System (CNDSS). In response to rising rates of syphilis, all provinces and territories (P/Ts) have also submitted enhanced surveillance data on infectious syphilis to the Public Health Agency of Canada through the Syphilis Outbreak Investigation Coordinating Committee (SOICC) starting in 2018. Descriptive analyses of CNDSS and SOICC surveillance data 2011-2020 by age, sex, pregnancy status, male sexual orientation and P/Ts were performed.

Results: The national rate of infectious syphilis increased from 5.1 per 100,000 population in 2011 to 24.7 per 100,000 population in 2020.The rates increased in almost all P/Ts, with the Prairie provinces reporting the greatest relative increases from 2016 to 2020 (more than 400%). Rates in males were consistently higher than rates in females over the past 10 years; however, from 2016 to 2020, rates among females increased by 773%, compared with 73% among males. Although the proportion of cases who self-identify as gay, bisexual and other men who have sex with men decreased from 54% to 38% between 2018 and 2020, they still represent a high proportion of cases (according to data from eight P/Ts). From 2016 to 2020, rates of infectious syphilis increased in every age group, especially in females aged 15-39 years. Confirmed early congenital syphilis cases for 2020 increased considerably from prior years, with 50 cases reported in 2020, compared with 4 cases in 2016.

Conclusion: Infectious and congenital syphilis rates are a growing concern in Canada and the nature of the syphilis epidemics across Canada appears to be evolving, as evidenced by recent trends. More data and research are needed to better understand the drivers associated with the recent changes in the epidemiology of syphilis in Canada.