TTC Cooling Tower Linked to Legionnaires' Outbreak, Health Officials Say

Toronto Public Health announced in August 2026 that a cooling tower at a Toronto Transit Commission (TTC) facility is the source of a legionnaires' disease outbreak affecting the city. The agency confirmed six individuals have tested positive for the infection, which is caused by Legionella bacteria.

The public‑health investigation traced the bacteria to aerosolized water released from the TTC cooling tower, contaminating the surrounding air. Legionella thrives in warm water systems and can become airborne when water is dispersed as a fine mist, creating a risk for people who inhale the contaminated droplets.

Legionnaires' disease is a severe form of pneumonia that can lead to serious complications, particularly in older adults, smokers, and those with weakened immune systems. The disease spreads when individuals breathe in water droplets that contain the bacteria, a route commonly associated with cooling towers, hot tubs, and large plumbing systems.

The identification of the TTC cooling tower as the outbreak source follows standard environmental sampling and laboratory testing performed by Toronto Public Health. The agency’s findings confirm that the Legionella bacteria present in the tower’s water system were the same strain detected in the six confirmed patients.

While the number of cases remains limited, health officials emphasized the importance of monitoring and maintaining cooling towers to prevent similar incidents. The TTC facility in question is located within the city’s transit network, and the contaminated air would have been dispersed in the vicinity of the tower.

Toronto Public Health continues to advise anyone experiencing symptoms of Legionnaires' disease—such as cough, fever, shortness of breath, or muscle aches—to seek medical attention promptly. Ongoing surveillance will track any additional cases that may be linked to the identified source.

The outbreak underscores the role of municipal water systems in public‑health safety and the need for regular inspection and remediation of potential bacterial growth sites.