London, Ont. faces deadly legionnaires’ outbreaks, raising concerns about how climate change may boost the spread of Legionella bacteria.
Rising Cases Amid Deadly Outbreaks
London, Ontario, is grappling with its second deadly legionnaires’ outbreak since the summer of 2024, resulting in six confirmed deaths. Public health officials say an industrial cooling tower in the city’s east, linked to Sofina Foods Inc., is the likely source. Legionella bacteria, which thrive in warm, moist, and stagnant water, can cause severe respiratory illness when inhaled as aerosolized droplets.
Climate Factors Amplifying Risk
Experts increasingly point to climate change as a contributing factor. “Temperature is definitely a driver,” said Juliette O’Keeffe, a senior scientist at the National Collaborating Centre for Environmental Health. Warm days create ideal conditions—between 25°C and 45°C—for Legionella growth, while extended use of cooling systems can further accelerate bacterial spread.
Humidity and rainfall also play significant roles. Outbreaks are more common in hot, humid regions such as southwestern Ontario and the East Coast. “Legionella is dispersed from cooling towers in aerosols,” O’Keeffe explained. “In humid environments, they persist longer.”
National Trends and Reporting Challenges
The Public Health Agency of Canada reports a dramatic rise in Legionella infections since 2004, though experts note many cases go unreported. Increased diagnostic capabilities account for some of the rise, but scientists believe environmental factors are contributing to a genuine increase in infections.
Cross-Border Concerns
Legionella is not confined to Canada. Joan Rose, director of the Water Alliance at Michigan State University, emphasized that outbreaks and general cases have been rising in the U.S. as well. “More frequent rainfall and warming conditions are likely stimulating bacterial growth and movement,” Rose said, echoing Canadian research findings.
Calls for Stricter Controls
Researchers stress the importance of tighter regulations and improved disinfection practices. Provinces like Quebec, New Brunswick, Hamilton, and Vancouver enforce strict cooling tower registration and safety measures, while Ontario currently lacks comparable rules. O’Keeffe and Rose both advocate for consistent monitoring and maintenance to reduce exposure risk.
Looking Ahead
With climate change intensifying heat, humidity, and rainfall patterns, public health experts warn that Legionella outbreaks could become more frequent. Ongoing research and stronger regulatory frameworks are seen as essential steps to mitigate the public health threat posed by these waterborne bacteria.
