A cooling tower at the Toronto Transit Commission’s (TTC) Hillcrest Complex is the source of a recent legionnaires’ disease outbreak in the city, according to Toronto Public Health (TPH). 

The environmental samples collected from the cooling tower matched a clinical sample from a confirmed case of the disease, a health official said in a TPH news release Tuesday.

Public health officials announced last week they were investigating an outbreak of six cases in a one-kilometre radius of the intersection of Bathurst and Dupont streets. Officials said the cases involved people who live, work in or visited the area and that they developed symptoms between July 2 and July 26.  

There were no deaths among those cases, TPH said in its Tuesday release.

TPH worked closely with the TTC throughout the investigation, the release said. 

“The affected cooling equipment was taken offline as soon as it was identified, and remediation measures are being undertaken in accordance with public health guidance,” Dr. Shima Shakory, TPH associate medical officer of health, said in the release.

There is no longer a legionella risk to the community, Dr. Michelle Murti, TPH’s Medical Officer of Health said.

Because legionella is a bacterial infection in the environment, it does not spread between people, explained Murti. 

“The environmental source is typically water at a certain temperature,” Murti told CBC News. “That’s why cooling towers are one of the most common sources of legionella infection, because they are large water sources with heated water that is also spraying that water into a large area.” 

Murti says the mist sprayed when the towers cool buildings can travel up to two kilometres away, which is how people are exposed to legionella. 

TPH has identified a possible epidemiological link between this outbreak and a previous outbreak at Castleview Wychwood Towers Long-Term Care Home, as both occurred in the same area at the same time, according to the update.

There were five confirmed cases at the long-term care home. No new cases have been reported at there.