Severe pneumonia outbreak tied to Legionella bacteria

The Simcoe Muskoka District Health Unit is investigating an outbreak of Legionnaire's disease in Orillia, Oct. 7, 2022 (CTV NEWS)

A recent outbreak of Legionnaires’ disease in southwestern Ontario has raised concerns about potential further spread and the risks posed by contaminated water systems during summer months.

Legionnaires’ disease is a severe form of pneumonia caused by Legionella bacteria, which are naturally found in freshwater environments.

“Legionnaire’s disease is one of the two diseases that are caused by this Legionella bacteria,” Dr. Dale Kalina Samji said in an interview with CTV News Channel Wednesday. “It is a pneumonia, essentially, compared with the less severe Pontiac fever, which is a fever illness.”

The disease is not spread person to person, as people become infected by inhaling water droplets containing the bacteria. The risk is especially high for older adults, smokers, those with chronic lung disease or anyone who is immunocompromised.

“It’s a severe pneumonia that can be treated with antibiotics, as well,” Kalina said, adding some patients may also experience gastrointestinal symptoms like nausea, vomiting or diarrhea.

The health unit in London, Ont., confirmed this week that more than 40 cases of legionella have been confirmed within a six-kilometre radius, with one person confirmed dead.

The bacteria can multiply rapidly in human-made water systems, including hot tubs and large plumbing networks.

“Legionella loves water,” said the infectious diseases specialist, adding it thrives in water-borne areas like air conditioning, CPAP masks and even cooling towers.

Kalina said hot weather might have to do something with the Legionnaires’ disease outbreak because it is associated with water.

“Here in southern Ontario … we’ve had multiple heat waves,” he said. “Interestingly in London, of course, they’ve got the outbreak right now, but they also had an outbreak similarly last year as well, and it’s likely associated with similar contexts of cooling towers, and air conditioning.”

With files from CTV News London Digital Lead Producer Kristylee Varley