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 (2002 to 2011). Longer-term secular trends and international comparisons are presented for context.
Chlamydia continues to be the most commonly reported STI in Canada. Since 2002, reported rates of chlamydia infection have increased by 61.8%. A steady increase in rates has continued in both sexes and across all age groups, the highest relative increase occurring among males. As in previous reports’ findings, in 2011 the reported rate among females (378.7 per 100,000) was almost twice as high as that among males (200.1 per 100,000). The highest rates of chlamydia were reported in those between the ages of 20 and 24 in both males and females. The distribution of reported cases of chlamydia varied geographically across Canada; the highest rates were observed in the Northwest Territories, Yukon, Manitoba, and Saskatchewan.
Between 2002 and 2011, the overall rate of reported cases of gonorrhea increased by 40.8%. The reported rate, as in previous years, was higher among males than females (38.4 vs. 27.8 per 100,000 respectively) in 2011. Females between the ages of 15 and 24 and males between the ages of 20 and 24 accounted for the highest reported rates of gonorrhea. The highest gonorrhea rate was observed in the Northwest Territories.
The overall rate of reported cases of infectious syphilis has increased by 231.8% since 2002. As before, the rate was higher among males than females (9.6 vs. 0.7 per 100,000) in 2011. Reported rates of infection among men were the highest in those aged 25 to 29 and among women in those aged 20 to 24. In 2011, infectious syphilis rates varied geographically, and the highest rates were observed in Quebec and New Brunswick.
Increases in reportable STI rates in recent years have been similarly observed in Australia, England, and the United States. In 2011, patterns in reportable STIs in these three comparison countries were similar to those in Canada. In all four countries, chlamydia was the most commonly reported STI, and reported rates of chlamydia were higher among females than males. Consistent with findings in Canada, reported rates of infectious syphilis in 2011 were higher among males than females in all three comparison countries. Reported rates of gonorrhea in 2011 were more than twice as high among males as females in Australia and England; in Canada and the United States, rates were more similar between the sexes. 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 reported cases of STIs have continued to increase 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 diagnosed. 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.