A legionnaires’ disease outbreak in London has been declared again after 25 new cases appeared, but health officials say they now believe they have found the source.
The Middlesex-London Health Unit (MLHU) said Tuesday that this year’s outbreak has led to 94 confirmed cases, including 86 hospitalizations and four deaths. The outbreak was first confirmed in early July and was declared over on August 6, before the recent rise in cases.
Officials said nine cooling towers across the city tested positive for Legionella bacteria, which causes legionnaires’ disease. Further testing showed that the strain found at Sofina Foods matched the one linked to the outbreak.
Cooling towers are large air-conditioning systems on top of buildings. Even with routine cleaning, bacteria can sometimes survive and grow again in warm, humid weather, the health unit said.
The disease does not spread through food, water, or person-to-person contact. Instead, people can get sick by breathing in tiny droplets of water carrying the bacteria. MLHU stressed that food from Sofina Foods is safe to eat.
Sofina Foods’ chief safety officer, Sharon Begley, said the test results were “unexpected” because the company already has strict cleaning and testing programs. She said the cooling tower has been shut down, deep-cleaned, and will stay offline until further testing confirms there is no risk.
The outbreak has mostly affected people in an area between Highbury Avenue North and Adelaide Street South, and Dundas Street to Hamilton Road. So far, most patients are adults, with 57 between ages 18–64 and 38 over 65. No children have been affected.
Legionnaires’ disease can cause fever, chills, cough, muscle aches, and headaches. Symptoms usually appear 2 to 10 days after exposure.
This year’s outbreak is much larger than one in 2024, which saw 30 cases and two deaths.
Dr. Joanne Kearon, associate medical officer of health, said:
“For several weeks, we saw no new cases and hoped the bacteria was gone. Unfortunately, 25 more people became sick. The good news is we now have a likely source.”
MLHU said it is working with Sofina Foods to make sure all risks are removed. The health unit will also provide weekly updates as the investigation continues.
