Chlamydia is the most commonly reported sexually transmitted infection caused by the bacteria Chlamydia trachomatis. Chlamydia often goes undiagnosed because the majority of infected people do not have symptoms. For more information, see the health unit’s fact sheet on chlamydia. The health unit offers confidential sexual health clinics in six locations for counseling, testing and treatment of sexually transmitted infections.
Simcoe Muskoka
Ontario
By Age Group
By Sex
Technical Notes
Simcoe Muskoka
The following graph shows the number of chlamydia cases in Simcoe Muskoka between 2000 and 2021. Chlamydia is the most commonly reported infectious disease in Simcoe Muskoka and Ontario. The majority of people infected with chlamydia have no symptoms so these numbers do not represent all infections. Between 2000 and 2021, there has been a four-fold increase in the number of chlamydia cases in Simcoe Muskoka, with 1,217 cases reported in 2021. The consistent increase since the mid-1990’s may partially be a result of increased testing. The drop in cases in 2020 and 2021 may relate to both behaviour changes and access to health services during the COVID-19 pandemic. The most reported risk factors among local chlamydia cases are
- No condom use
- Multiple partners in past six months
- New partner in past two months.
The following graph shows the age-standardized incidence rates (ASIR) of chlamydia in Simcoe Muskoka and Ontario between 2005 and 2021. The ASIR in Simcoe Muskoka and Ontario have increased since 2005. Historically, the Simcoe Muskoka ASIR was lower than the Ontario ASIR, however the rates have converged in recent years. In Simcoe Muskoka, the ASIR of chlamydia for 2021 was 222.8 cases per 100,000 population. In comparison, the ASIR of chlamydia for the same time period for all of Ontario was 424.5 cases per 100,000 population.
The graph below shows the age-specific incidence rates of chlamydia in Simcoe Muskoka between 2000 and 2021. The highest rate is among 15-24 year-olds at 934.8 cases per 100,000 population in 2021. Those aged 25-39 years of age had the next highest incidence rate at 388.3 cases per 100,000 population.
The following graph shows the sex-specific incidence rates of chlamydia in Simcoe Muskoka from 2000 to 2021. Females have a higher incidence of chlamydia than men in Simcoe Muskoka. In 2021, the incidence rate of chlamydia in Simcoe Muskoka males was 145.2 cases per 100,000 population, while the female incidence rate was 249.6 cases per 100,000 population. This is in part due to the lack of symptoms experienced by men infected with chlamydia and a higher proportion of females being tested as they visit health care providers more frequently than males.
More detailed data for Ontario and each health unit can be found on Public Health Ontario’s interactive Reportable Disease Trends in Ontario tool.
There are many factors that influence how many cases are reported to the health unit, as explained on the Infectious Diseases page. It is unclear to what extent the global COVID-19 pandemic has influenced the reporting and spread of other infectious diseases – counts and rates of disease since 2020 should be interpreted with caution.
Age-standardization: The
incidence rate of chlamydia varies significantly between age groups so standardization is necessary to compare rates between two populations. For example, the highest incidence rate of chlamydia is found among 15-24 year olds. Simcoe Muskoka may have a different proportion of people in this age group than Ontario, so both rates must be applied to a standard population to compare them. More information about Simcoe Muskoka’s population can be found under the
Population topic.
Page last updated August 19, 2022