Sexually transmitted infections (STIs) continue to be a significant public health concern in Canada. Rates of reported cases of chlamydia, gonorrhea, and infectious syphilis have been rising since the late 1990s. This report describes the trends and patterns in these three nationally reportable STIs in Canada, focusing on the past decade (2003 to 2012). Longer-term secular trends and international comparisons are presented for context.
Chlamydia. Chlamydia continues to be the most commonly reported STI in Canada. Between 2003 and 2012, rates of reported cases of chlamydia increased by 57.6%, from 189.6 to 298.7 per 100,000. Rates increased in both sexes and across all age groups, with the highest relative rate increase occurring among males. In 2012, accordant with previous reports' findings, the rate of reported cases of chlamydia among females (383.5 per 100,000) was almost twice as high as that among males (212.0 per 100,000). In both males and females, rates of chlamydia were highest in those aged 20 to 24 years. There was significant variability in the rates of reported cases of chlamydia across Canada; rates above the national average were observed in the Northwest Territories, Manitoba, Saskatchewan, Yukon, and Alberta.
Gonorrhea. Between 2003 and 2012, the rate of reported cases of gonorrhea increased by 38.9%, from 26.0 to 36.2 per 100,000. Over this time frame, a greater relative rate increase was observed in females, though rates of gonorrhea increased in both sexes and across all age groups. In 2012, as in previous years, the rate of reported cases of gonorrhea was higher in males than females (41.4 vs. 31.0 per 100,000). Females between the ages of 15 and 24 years and males between the ages of 20 and 29 years accounted for the highest rates of gonorrhea in 2012. The highest rate of reported cases of gonorrhea was observed in the Northwest Territories.
Infectious syphilis. Rates of reported cases of infectious syphilis increased by 101.0% between 2003 and 2012, from 2.9 to 5.8 per 100,000. Over this time frame, rates increased among males by 128.3% and decreased among females by 40.9%. In 2012, as in previous years, the rate of reported cases of infectious syphilis in males was markedly higher than that in females (11.0 vs. 0.5 per 100,000). In males, rates of infectious syphilis were highest among those aged 25 to 29; in females, rates were highest among those aged 20 to 24. In 2012, infectious syphilis rates varied geographically, and the highest rates occurred in Quebec.
Increases in reportable STI rates in recent years have been similarly observed in Australia, England and the United States. As in Canada, chlamydia was the most commonly reported STI in 2012 and rates were considerably higher among females as compared to males in all three countries. Gonorrhea patterns across the four countries were more varied; in Australia and England, the gonorrhea rates in males were more than double those in females, while the difference between sexes in Canada and the United States was less pronounced. Consistent with 2012 findings in Canada, rates of reported cases of infectious syphilis were substantially higher among males than females in all three countries. Overall, rates of chlamydia and gonorrhea were lower in Canada as compared to the other three countries but more similar for infectious syphilis.
Rates of reportable STIs have increased despite numerous public health interventions designed to prevent, diagnose, and treat infection. There are various potential factors that may explain these observations. For instance, more sensitive laboratory tests used to detect chlamydia and gonorrhea have increased the number of these infections that are identified. More effective screening and contact tracing methods may also improve case finding. Antimicrobial resistance, a particular concern in gonorrhea, may result in treatment failure and continued transmission of infection. Finally, changes in sexual practices may increase the number of people contracting STIs, as evidenced by the syphilis outbreaks seen across Canada.
National statistics and trends in STIs are used to inform public health programs, guidelines, and recommendations. In response to this growing public health issue, the Agency produces guidelines for health professionals and educators on the prevention, diagnosis, and treatment of these infections. They can be accessed at the Sexual Health and Sexually Transmitted Infections website or the CATIE Ordering Centre.