Simcoe Muskoka District Health Unit has declared an outbreak of Legionnaires’ disease in Orillia over and said it has found the source of the bacteria.
The health unit investigated 27 known cooling towers at 17 sites in Orillia and tested 10 sites.
Health officials say they discovered a strain of Legionella in the Orillia Rotary Place cooling tower that was a genetic match with one sputum sample of a case of Legionnaires’ disease among the 35 cases.
“We are confident that with the testing, monitoring and completion of any required cleaning and disinfection of the cooling towers that continue to operate in Orillia at this time, there is no further risk of transmission associated with this outbreak. As such, the health unit is declaring the conclusion of this outbreak,” said Dr. Charles Gardner, SMDHU medical officer of health.
Health officials say they could not test for the source of the other 34 cases and that testing could not be done for seven sites as they had been shut down for the season before testing could be completed.
The cooling towers in operation in Orillia that the health unit has identified are being closely monitored, officials say.
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Legionnaires’ disease is a type of lung infection caused by the bacteria, with people over 50, smokers, or those with certain medical conditions at an increased risk.
Health officials say most people exposed to the bacteria do not become ill.
The bacteria is commonly found in natural freshwater environments.
It can become a health concern in water systems, such as cooling towers, plumbing systems in large buildings, humidifiers, hot tubs and spas, and decorative fountains, when conditions allow the bacteria to multiply.
Since undergoing repairs at the end of October, the health unit said testing of the Rotary Place cooling towers every few days led to the detection of low levels of Legionella bacteria within the cooling tower on Monday.
The health unit said that while the levels were not high enough to be an active risk to the community, the City of Orillia determined that the safest option was to shut down the cooling tower until a root cause could be determined.
“The health and safety of our community is absolutely paramount. The most recent testing identified low levels of Legionella, and keeping the cooling tower at Rotary Place operational is not a risk that we are willing to take,” said Mayor Steve Clarke.
“The City has done everything we can operationally at this time. There are no legislated standards regarding the operation of cooling towers. The City will continue to rely on the advice and recommendations of industry experts, including a specialized engineering firm, to analyze the system for a plan of action moving forward.”
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