Infectious syphilis and congenital syphilis in Canada, 2023

Infectious syphilis and congenital syphilis in Canada, 2023^{Note *}

Social and structural determinants of health and health inequities play a role in the differences in rates of syphilis across different populations^{Note ‡‡}.

Syphilis screening and timely treatment are essential to prevent transmission and complications. Find the Public Health Agency of Canada (PHAC)’s recently updated syphilis screening recommendations in the Syphilis Guide: Screening and diagnostic testing, as part of PHAC’s Sexually transmitted and blood-borne infections (STBBI): Guides for Health Professionals.

Infectious syphilis

In 2023, there were 12,135 cases of infectious syphilis^{Note **} reported nationally, for a rate of 30.5 cases per 100,000 population. The 2023 national rate of infectious syphilis was:

• 16% lower than the 2022 rate
• 77% higher than the 2018^{Note ┼} rate

It is the first year since 2014 that the national number of cases and rate of infectious syphilis have decreased. However, data for 2023 alone cannot be viewed as a trend and must be interpreted with caution. Future data collection is needed to determine if a downward trend in infectious syphilis rates is being established^{Note ѱ}.

The national reported rate of infectious syphilis increased by 32% from 2014 to 2015 and by 20% from 2015 to 2016. The rate remained relatively stable from 2016 to 2017, with a 5% increase. Substantial increases in the national reported rate of infectious syphilis were seen in subsequent years^{Note ४}:

• From 2017 to 2018, an increase of 52%
• From 2018 to 2019, an increase of 42%
• From 2019 to 2020, a relatively stable rate, with an increase of 2%^{Note ѱ}
• From 2020 to 2021, an increase of 30%^{Note ѱ}
• From 2021 to 2022, an increase of 13%^{Note ѱ}

Trends by sex

Nationally, 64% of cases reported in 2023 occurred among males, with a male-to-female ratio of 1.8. In comparison, in 2018, 79% of cases occurred among males, with a male-to-female ratio of 3.8 (see Appendix A, Table 5, for trends by gender).

• In 2023, the national reported rate of infectious syphilis increased by 204% in females and by 43% in males, compared to 2018

Trends by sex and age group

In 2023, national reported rates of infectious syphilis were highest in the 20- to 39-year age group (see Appendix A, Table 6 and Table 7). The rates were highest:

• In the 25–29- and 30–39-year age group for males
• In the 20–24- and 25–29-year age group for females

In 2023, males aged 30–39 years had the highest national rate of infectious syphilis of any age group, male or female, at 90.4 cases per 100,000 males aged 30–39 years. Followed closely were males aged 25–29 years, with a rate of 81.7 cases per 100,000 males aged 25–29 years.

• Rates in 2023 increased relative to 2018 across all age groups, with the highest rate increases occurring among 30–39- (46%) and 40–59-year-olds (67%)
• Rates in 2023 decreased relative to 2022 among most age groups, with the highest rate decreases occurring among 15–19- (24%) and 20–24-year-olds (21%)
• The rate in 2023 among those under 15 years increased by 32% relative to 2022

Among females, those aged 20–24 years had the highest national rate of infectious syphilis, at 67.4 cases per 100,000 females aged 20–24 years, followed by those aged 25–29 years, with a rate of 66.2 cases per 100,000 females aged 25–29 years.

• Rates in 2023 increased relative to 2018 among all age groups, with the highest rate increases occurring among 30–39- (243%) and 40–59-year-olds (444%)
• Rates in 2023 decreased relative to 2022 among most age groups, with the highest rate decreases occurring among 25–29- (22%) and 30–39-year-olds (23%)
• The rate in 2023 among those over 60 years increased by 24% relative to 2022

Trends by sexual behaviour

Cases of infectious syphilis reported among cisgender gay, bisexual and other men who have sex with men (GBMSM)^§ represented 27% of all reported cases in 2023 (see Appendix A, Table 8).

• GBMSM represented 42% of total reported male cases in 2023, a 1% increase from 2022 and a 37% decrease from 2018
• The number of reported cases among GBMSM has remained relatively stable throughout time, even as the proportion of cases among GBMSM relative to cases in the total population (combined infectious syphilis cases among males, females, etc.) has decreased

Trends by province and territory

• Between 2014 and 2022, there was an upward trend in the reported number of cases and rates of infectious syphilis across all provinces and territories. However, 2023 has been characterized by non-uniform changes in case counts and rates across jurisdictions. Provincial and territorial data in 2023 are as follows:
  • Rates in 2023 decreased relative to 2022 in most provinces and territories, with the highest rate decreases occurring in Alberta and Manitoba (31% and 24%, respectively)
  • Rates in 2023 increased relative to 2022 in Newfoundland and Labrador, Nunavut and Québec (data not shown [DNS] to reduce the risk of identifying individuals, 137% and 6%, respectively)
  • In 2023, the highest number of reported cases of infectious syphilis occurred in Ontario (n=3,189), followed by Alberta (n=2,380), Saskatchewan (n=1,913) and Manitoba (n=1,487)
• Provinces and territories that reported rates of infectious syphilis higher than the national rate of 30.5 cases per 100,000 population included:
  • Northwest Territories (311.1 cases per 100,000 population)
  • Nunavut (269.3 cases per 100,000 population)
  • Saskatchewan (159.3 cases per 100,000 population)
  • Yukon (132.3 cases per 100,000 population)
  • Manitoba (103.0 cases per 100,000 population)
  • Alberta (51.2 cases per 100,000 population)
• Provinces and territories that reported rates of infectious syphilis lower than the national rate of 30.5 cases per 100,000 population included:
  • British Columbia (25.1 cases per 100,000 population)
  • Ontario (20.6 cases per 100,000 population)
  • Québec (15.5 cases per 100,000 population)
  • Newfoundland and Labrador (DNS)
  • New Brunswick (4.7 cases per 100,000 population)
  • Nova Scotia (4.4 cases per 100,000 population)
  • Prince Edward Island (DNS)

Trends by sex and by province and territory

In 2023, the proportion of males with infectious syphilis, relative to females, varied across provinces and territories (see Appendix A, Table 9).

• Provinces and territories that reported a male-to-female rate ratio lower than the national ratio of 1.8 or, in other words, had a higher proportion of females impacted than the national average, included:
• Saskatchewan (rate ratio: 0.8)
• Manitoba (rate ratio: 0.9)
• Yukon (rate ratio: 1.0)
• Nunavut (rate ratio: 1.0)
• Northwest Territories (rate ratio: 1.2)
• Alberta (rate ratio: 1.2)
• Prince Edward Island (rate ratio: 1.6)

Congenital syphilis

In 2023, there were 53 cases of confirmed early congenital syphilis^{Note ╪} reported nationally, for a rate of 14.5 cases per 100,000 live births. The 2023 national rate of confirmed early congenital syphilis was:

• 56% lower than the 2022 rate
• 220% higher than the 2018^{Note ┼} rate

From 2018 to 2022, national reported rates of confirmed early congenital syphilis increased annually. However, in 2023, the rate decreased, in parallel with the decrease in the reported rate of infectious syphilis among females aged 15–39 years.

As with infectious syphilis, it is the first year since 2014 that the national number of cases and rate of congenital syphilis have substantially decreased. However, data for 2023 alone cannot be viewed as a trend and must be interpreted with caution. Future data collection is needed to determine if a downward trend in congenital syphilis rates is being established^{Note ѱ}.

In 2023, following annual increases from 2018 to 2022, the rate of infectious syphilis among females aged 15–39 years decreased.

• The 2023 national reported rate of infectious syphilis among females aged 15–39 years was:
• 21% lower than the 2022 rate
• 176% higher than the 2018 rate

In 2023, there were 174 cases of congenital syphilis, including confirmed early congenital syphilis, probable early congenital syphilis, syphilitic stillbirth and unknown-stage congenital syphilis^{Note ╪}.

Trends by province and territory

Between 2014 and 2022, there was an upward trend in the reported number of cases and rates of congenital syphilis across all provinces and territories. However, in 2023, the reported number of cases of confirmed early congenital syphilis decreased or remained stable across jurisdictions. Provincial and territorial data in 2023 are as follows:

• Rates in 2023 decreased relative to 2022 in British Columbia (24%), Alberta (78%), Saskatchewan (65%), Manitoba (50%) and Ontario (55%). However, an increase in reported case counts was observed in Québec (107%) and Yukon (rate change not computable)
• There were no cases of confirmed early congenital syphilis reported in New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador and Nunavut
• Case counts remained stable in the Northwest Territories
• Within the context of decreasing national case counts, the highest number of confirmed early congenital syphilis cases reported, overall, in 2023 occurred in Ontario (n=13; rate=9.1 cases per 100,000 live births, 55% decrease) and Manitoba (n=12; rate=68.0 cases per 100,000 live births, 50% decrease)
• Provinces and territories that reported rates of congenital syphilis higher than the national rate of 14.5 cases per 100,000 live births included:
  • Northwest Territories (DNS)
  • Yukon (DNS)
  • Manitoba (68.0 cases per 100,000 live births)
  • Saskatchewan (DNS)
  • Alberta (DNS)
• Provinces and territories that reported rates of congenital syphilis lower than the national rate of 14.5 cases per 100,000 live births included:
  • Ontario (9.1 cases per 100,000 live births)
  • British Columbia (DNS)
  • Québec (DNS)
  • New Brunswick (0.0 cases per 100,000 live births)
  • Nova Scotia (0.0 cases per 100,000 live births)
  • Prince Edward Island (0.0 cases per 100,000 live births)
  • Newfoundland and Labrador (0.0 cases per 100,000 live births)
  • Nunavut (0.0 cases per 100,000 live births)

To learn more about syphilis, visit: www.canada.ca/syphilis.

Appendix A: List of supplementary tables

The supplementary tables described below are available upon request via sti-hep-its@phac-aspc.gc.ca.

• Table 5: Number and proportion of reported cases of infectious syphilis by gender, Canada, 2018–2023^{Note ४}
• Table 6: Rates per 100,000 population of reported cases of infectious syphilis by age group, Canada, 2014–2023^{Note ४}
• Table 7: Rates per 100,000 population of reported cases of infectious syphilis by sex and age group, Canada, 2014–2023^{Note ४}
• Table 8: Number of reported cases of infectious syphilis by sexual behavior, Canada, 2018–2023^{Note §Note ४}
• Table 9: Reported cases and rates per 100,000 population of infectious syphilis by sex and by province and territory, 2023^{Note ¥}