Thirteen legionnaires’ disease cases confirmed in Hamilton: public health officials

HAMILTON — Hamilton Public Health says it is investigating a cluster of 13 confirmed cases of legionellosis, also known as legionnaires’ disease, an infection caused by bacteria found primarily in warm water environments.

Public health officials say the cases have been reported since Monday, and hospitals have been notified to watch for potential cases.

They say the agency is working to identify the sources of exposure, focusing on east Hamilton or Stoney Creek.

Hamilton Public Health says no common source has been identified at this time, and possible sources of exposure include nearby cooling towers.

The disease is spread when people breathe in small water droplets containing the bacteria, which are not spread from person to person.

“We have identified a cluster of legionellosis cases in the east end of the city and are focused on identifying potential sources of exposure,” said Dr. Brendan Lew, associate medical officer of health for Hamilton.

“We are working closely with local partners and reminding residents and facility operators of the importance of properly maintaining water systems and mist-producing devices.”

Toronto public health officials said earlier this week that nine cases of legionnaires’ disease had been confirmed there and the agency was investigating the source of the outbreak.

Legionnaires’ disease is caused by legionella bacteria that can lead to pneumonia, with symptoms that may include high fever and chills.

It occurs more often in individuals aged 50 and over, individuals with weakened immune systems such as organ transplant patients and individuals with lung conditions, cancer, diabetes and smokers.

-by Maan Alhmidi in Toronto

This report by The Canadian Press was first published May 8, 2026.

The Canadian Press