Map of Simcoe Muskoka

Infectious Diseases


Cryptosporidiosis is a disease caused by the parasite Cryptosporidium. Some people with cryptosporidiosis do not have any symptoms. The most common symptoms are frequent, watery diarrhea and stomach cramps. Cryptosporidiosis is spread by consuming contaminated food or water, swimming in contaminated water, or contact with infected pets or farm animals. For more information, see the health unit's fact sheet on cryptosporidium.

Simcoe Muskoka
Technical Notes

Simcoe Muskoka

The following graph shows the number of cryptosporidiosis cases in Simcoe Muskoka between 2000 and 2021. The number of cryptosporidiosis cases in Simcoe Muskoka varies between two and 24 cases per year, except for the increases observed in 2006, 2018 and 2019. In 2021, 24 cases of cryptosporidiosis were reported to the health unit.

In 2006, there was an increase in cryptosporidiosis cases in Simcoe Muskoka and surrounding health units. Local and provincial experts could not find any common exposures or source during this time period. One contributing factor may have been the multiple heavy rainfalls in the spring and summer of 2006, which can increase the concentration of cryptosporidium parasites in lakes where people swim and unintentionally swallow water.

Changes in testing methodology by some labs in the province since mid-2017 may partly explain the increase in cases observed between 2017 and 2019. A local outbreak of cryptosporidiosis in 2018 also contributed to the high case count in 2018.



The following graph shows the incidence rate of cryptosporidiosis in Simcoe Muskoka and Ontario between 2000 and 2021. The incidence rate in Simcoe Muskoka is comparable to the Ontario rate, however it is more variable than the Ontario rate because it is based on smaller numbers. The Ontario rate has remained relatively stable between 2000 and 2017. The 2021 incidence rate for cryptosporidiosis was 3.5 cases per 100,000 population in Simcoe Muskoka and 3.9 cases per 100,000 population in Ontario.


More detailed data for Ontario and each health unit can be found on Public Health Ontario’s interactive Reportable 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.

Provincial definitions classify cases as confirmed or probable based on clinical and/or laboratory diagnostic criteria. The provincial case definition for cryptosporidiosis changed in April 2009 to include a definition for probable cases whereas before there was no such classification. The definitions of confirmed and probable cases from 2009 onwards are comparable to confirmed cases before 2009.

Changes in testing methodology by some labs in the province since mid-2017 may explain in part the increased incidence of cryptosporidiosis both locally and provincially.

Page last updated August 19, 2022