- Case counts (2016-2025), population estimates (2016-2023), & population projections (2024-2025): Public Health Ontario.
- Query: Case counts of reportable diseases by public health unit and year. Toronto, ON: Ontario Agency for Health Protection and Promotion; extracted on March 9, 2026.
Legionellosis
Legionella
Legionellosis is caused by a group of bacteria called Legionella species that are found in natural and man-made environments such as cooling towers, potable water systems, lakes, rivers, and streams. It can also be found in soil. Legionella can become a health concern when it grows in these water systems and devices, and is inhaled in the form of droplets and mists released into the air.
Local Information
2025 Statistics
Incidence rate is the number of new cases of disease divided by the number of persons at risk for the disease during a particular time period.
Cases:
1*
Incidence rate per 100,000 in 2025: 0.7
*Includes confirmed cases in 2025.
Incidence rate per 100,000 of legionellosis by year
More information about legionellosis
Public Health Agency of Canada
Ministry of Health
Report to the Health Unit within one next business day by fax (705-482-0670) or phone at 705-474-1400 or toll free at 1-800-563-2808, ext. 5229 if legionellosis is suspected or confirmed as per Ontario Regulation 135/18 and amendments under the Health Protection and Promotion Act, R.S.O., c.H.7.
Should one go to childcare, school, or work if they have Legionellosis?
No exclusion necessary. Person to person transmission has not been documented.
Healthcare provider information
Public Health Ontario
Ministry of Health - Ontario Public Health Standards
National Collaborating Centre for Infectious Diseases
Contact our Communicable Disease Control (CDC) program at 705-474-1400 or toll free at 1-800-563-2808, ext. 5229, or by email to cdc@healthunit.ca for more information.
Last updated: Mar 2026, by CDC
Do You Have a Cooling Tower?
In cooling towers used in air-conditioning and industrial systems, the water temperature create comfortable environments for legionella to grow.
To reduce health risks, follow industry standards for maintaining your cooling tower, and notify us of your cooling tower location