Chlamydia is a common 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 eight locations for counseling, testing and treatment of sexually transmitted infections.
By Age Group
The following graph shows the number of chlamydia cases in Simcoe Muskoka between 2000 and 2015. 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 2015, there was a three-fold increase in the number of chlamydia cases in Simcoe Muskoka resulting in 1234 cases reported in 2015. The consistent increase since the mid-1990’s may partially be a result of increased testing.
The following graph shows the age-standardized incidence rates (ASIR) of chlamydia in Simcoe Muskoka and Ontario between 2000 and 2015. The ASIR in Simcoe Muskoka and Ontario have increased since 2000. The Simcoe Muskoka ASIR used to be lower than the Ontario ASIR, however the rates have converged in recent years. In Simcoe Muskoka, the ASIR of chlamydia for 2015 was 240.5 cases per 100,000 population. In comparison, the ASIR of chlamydia for the same time period for all of Ontario was 284.4 cases per 100,000 population.
The graph below shows the age-specific incidence rates of chlamydia in Simcoe Muskoka between 2000 and 2015. The highest rate is among 15-24 year olds at 1177 cases per 100,000 population. While the rate among this age group as well as among 25-39 year olds increased significantly between 2010 and 2012, it has remained relatively stable since 2012.
The following graph shows the sex-specific incidence rates of gonorrhea in Simcoe Muskoka from 2000 to 2015. Females have a higher incidence of chlamydia than men in Simcoe Muskoka. In 2015, the incidence rate of chlamydia in Simcoe Muskoka males was 168 cases per 100,000 population, while the female incidence rate was 282 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 Snapshots tool, by clicking on “Select Indicator”.
There are many factors that influence how many cases are reported to the health unit, as explained on the Infectious Diseases page.
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.