Map of Simcoe Muskoka

Infectious Diseases


Syphilis is a sexually transmitted infection caused by the bacteria Treponema pallidum. Syphilis is spread by direct contact with a syphilis chancre/lesion, which occurs mainly on the external genitals, vagina, anus or in the rectum. Lesions can also occur on the lips and in the mouth. Transmission occurs during vaginal, anal or oral sex. In addition, an infected mother can pass syphilis to her baby during pregnancy or delivery.

Lesions are often not recognized as they are painless, thus most transmission is caused by people who are unaware of their infection. If syphilis is not treated early, it can progress to cause complications of the nervous system, cardiovascular system or tissue destruction of any organ. For more information, see the health unit's fact sheet on syphilis.

Simcoe Muskoka
By Age Group
By Sex
Technical Notes

Simcoe Muskoka

The following graph shows the number of infectious syphilis cases in Simcoe Muskoka between 2000 and 2021.  There have been between 3 and 83 cases of syphilis reported in Simcoe Muskoka every year since 2000, between one and 59 of which are infectious. In 2021, 83 cases of syphilis were reported in Simcoe Muskoka, 59 of which were infectious.



The following graph shows the age-standardized incidence rate of infectious syphilis cases in Simcoe Muskoka and Ontario between 2005 and 2021. The incidence rate in Simcoe Muskoka is lower than the Ontario rate. In 2021, Simcoe Muskoka’s infectious syphilis incidence rate was 4.4 cases per 100,000 population, which is more than double the rate reported in 2019.

The Ontario incidence rate increased significantly starting in 2002 due to an outbreak among men who have sex with men, primarily in Toronto and Ottawa.  In 2005, the rate decreased but a second increase was observed in 2009 among the same sub-population. In 2021, the infectious syphilis incidence rate for Ontario was 16.8 cases per 100,000 population. Provincially, infectious syphilis has been creasing year-over-year since 2014.


Age Grou

The following graph shows the age-specific incidence rate of infectious syphilis in Simcoe Muskoka between 2001 and 2021. There is a lot of variability in the age specific rates because they are based on small numbers of cases. Historically, the highest rates are among 25 to 39 year-olds and 15 to 24 year olds.


By Sex

The following graph shows the sex-specific incidence rate of syphilis in Simcoe Muskoka between 2000 and 2021. The incidence rate among males is higher than the incidence rate among females.


More detailed data for Ontario and each health unit can be found on Public Health Ontario’s interactive Infectious Disease Trends in Ontario tool.

Technical Notes

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.

Syphilis is considered to be infectious during the primary, secondary and early latent stages. Late latent stages are considered to be non-infectious. The syphilis cases that are not staged are classified as “unspecified”. In the figures on this page, the category of “other syphilis” includes non-infectious and unspecified syphilis cases.

Age-standardization: The incidence rate of infectious syphilis varies significantly between age groups so standardization is necessary to compare rates between two populations. For example, the highest incidence rate of infectious syphilis is found among 25-39 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