A legionnaires’ disease outbreak has been “re-declared” after a sudden rash of 25 new cases but officials now say they believe they’ve pinpointed the source of the outbreak.
“To date, the outbreak in 2025 has been linked to serious pneumonia in at least 94 London residents, resulting in 86 hospitalizations and four deaths,” the Middlesex-London Health Unit said Tuesday.
“The decision to reopen the outbreak reflects a rise in cases after several weeks without new cases, suggesting that the Legionella bacteria has re-emerged in the environment despite earlier remediation efforts.”
The outbreak, first confirmed in early July, had previously been declared over on Aug. 6.
A spokesperson for the health unit said nine cooling towers (air-conditioning units from large buildings) across the city tested positive for the bacteria that causes legionnaires’ and “further testing confirmed that the strain at Sofina Foods matched the one linked to this outbreak.”
The health unit also noted that “despite routine cleaning and disinfection trace bacteria can sometimes persist in cooling towers and regrow under hot, humid conditions.”
“Earlier testing at the facility in 2024 and early 2025 did not produce a match. In the last month, two rounds of testing were conducted; the first showed no match, while the second did, most likely because of bacterial regrowth between the tests.”
However, the spokesperson stressed that the disease is not spread through eating or drinking or through person-to-person contact, but rather through people breathing in small droplets of water containing the bacteria.
“It is found naturally in the environment in the soil or water. The bacteria is also common in cooling towers located on top of buildings. It is then aerosolized and can travel quite a distance in the wind,” he explained.
“Food products from Sofina Foods Inc. remain safe to consume.”
A heat map showing where the legionnaires’ disease outbreak has been concentrated.
Middlesex-London Health Unit
The outbreak is concentrated in the area between Highbury Avenue North and Adelaide Street South to the east and west and Dundas Street and Hamilton Road to the north and south. Of the 95 people confirmed to have become ill, 57 were between 18 and 64 years old and 38 were 65 and older. No confirmed cases have involved children, as of Tuesday.
The disease can cause fever, chills, a dry cough, potentially muscle aches and headaches. Symptoms usually begin two to 10 days after coming in contact with the bacteria, according to the health unit.
The outbreak is significantly larger than a 2024 outbreak, which saw 30 cases and two deaths.
“For several weeks, no additional illnesses were reported, and we were optimistic that remediation efforts had eliminated the bacteria. However, 25 more people have now become ill,” said Dr. Joanne Kearon, associate medical officer of health.
“Fortunately, a likely source has now been identified.”
The health unit said it is “working diligently to ensure comprehensive remediation” and that Sofina Foods Inc. has been “fully cooperative throughout the outbreak, following required protocols, and taking every necessary step to complete thorough remediation.”
Global News has reached out to Sofina Foods Inc. but had not received a response as of publication time.
With the re-declaration of the outbreak, the health unit will resume providing weekly updates.