London, Ontario is still dealing with its second deadly outbreak of Legionnaires’ disease since the summer of 2024. READ MORE: Legionnaires’ Disease This acute respiratory illness is largely due to the legionella bacteria. It calls for immediate answers to important questions regarding the impact climate change will have on public health. A recent report from Health Canada highlights the emerging link between rising temperatures and increased infection rates of this often-overlooked illness.
Legionella bacteria are naturally occurring in groundwater and surface water. As experts recently told Rep. Climate change could make things ripe for its spread. Joan Rose, director of the water alliance at Michigan State University, highlighted the importance of this pathogen. “Legionella is one of the most important waterborne pathogens we’re dealing with now,” she stated.
As Dominion Medicine explains, the Public Health Agency of Canada has released an alarm about the increase in one case of Legionnaires’ disease. As infections are often left unreported, the unjust scale of the epidemic may be even greater. Rose and Juliette O’Keeffe are currently both diving deep into research on how climate change is impacting the spread of legionella. Juliette is a principal science advisor at the National Collaborating Centre for Environmental Health.
The study found a relationship between heavy rainfall events and legionellosis outbreaks in England, Belgium, and the Netherlands. O’Keeffe noted, “Legionella is naturally occurring in groundwater and surface water. When you have these events, it mobilizes the bacteria, stimulates them to start growing.” Increased rainfall contributes to the spread of legionella. This is increasingly the case when warmer wintertime temperatures set the stage for its emergence and rapid spread. Rose explained that “if you have more warm days, you’re going to have more conditions that are favorable for legionella growth.”
In London, the cooling towers at a municipal facility have been found to be the source of such outbreaks. These systems are capable of aerosolizing legionella into aerosols—microscopic water droplets that can float and drift across a large expanse of space. In humid conditions, where these aerosols become even more dangerous, as they can remain suspended in the air much longer, the risk of exposure drastically increases.
Ontario is an exception so far — a jarring contrast to other provinces. Quebec, New Brunswick, Hamilton and Vancouver have jurisdiction-wide registration and enhanced safety standards for cooling tower operators. O’Keeffe highlighted the need for improved regulatory oversight: “We don’t have a lot of regulations that look at how we monitor, then how we report the information on this bacteria.”
O’Keeffe went on to argue that proper and ongoing maintenance of cooling towers is key to minimizing public exposure to legionella. “This isn’t really all that new. We know that cooling towers are a source. We know that maintaining them well is a way to reduce exposures and to keep that water clean,” she said.
The combination of higher temperatures and humidity levels in regions like southwestern Ontario and the East Coast contributes to an environment where legionella can thrive. O’Keeffe noted, “We’re seeing these increases in cases, but is that because we’re doing better at finding the cases or is there something happening out there that’s causing more increases in growth or dispersion of the bacteria?”
London is no stranger to recurrent outbreaks of Legionnaires’ disease. Public health officials need to address climate change as a definitive factor fueling the surge in cases. The public health risk communities continue to be under attack by this pernicious and lethal bacterium. Now, we need to make the right investments and rules to keep them safe.
