Officials offer new details in London’s deadly legionnaires’ disease outbreak

London’s public health agency has found evidence of bacteria in several water systems they’ve tested as they continue to investigate a deadly local outbreak of legionnaires’ disease.

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As of Wednesday afternoon, there were 24 confirmed cases, up from 22 last Friday, with one death and four people in hospital. All cases were treated in hospital at some point during the course of their illness, officials said.

During a Wednesday press conference, Middlesex-London Health Unit officials said they’ve tested a dozen cooling towers and found evidence of legionella, the bacteria that causes legionnaires’ disease, at three of them. Cooling towers are a water-cooling device used in HVAC and industrial systems.

Legionnaires’ disease is a severe respiratory infection that can cause fever, chills and a dry cough. The bacteria responsible can be found in warm water sources such as air-conditioning systems, hot water tanks and heaters and plumbing systems.

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The Middlesex-London Health Unit was notified on July 24 about a cluster of cases that first appeared to be pneumonia. Two days later, officials declared an outbreak of legionella.

Joanne Kearon, the associate medical officer of health, said that while the exact origin of the exposures hasn’t been found, they’re looking at large, outdoor, industrial cooling systems.

“This is what we would consider a community outbreak, rather than being linked to a single, multi-dwelling residence or workplace. It’s not related to an indoor exposure,” she said.

Most of the cases have been people who live or work in the same five-kilometer area of ​​southeast London, which has not been publicly identified.

Kearon said there are still too many variables, from the timeline to the area being investigated, to narrow it down further. Identifying the area “would not help people understand their personal risk or take any actions to reduce their risk” based on how the bacteria spreads, she said.

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Legionnaires’ disease is not considered contagious in person-to-person transmission, but is spread when the bacteria is blown around by fans or wind and people breathe it in.

Symptoms of legionnaires’ disease usually begin two to 10 days after a person is exposed to the bacteria. Those most at risk are older, have lung problems or are immune-compromised.

The samples collected from the cooling towers are sent to Public Health Ontario, which advises local officials, to test the samples for matches with human samples.

Kearon said it’s possible, given the large search area and the lifespan of the bacteria, that no source of the outbreak will be identified. But if it’s found, the risk already will be gone: Kearon said public health workers have pushed operators to sanitize their systems after samples were taken.

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Kearon added all the sites tested had maintained sanitation records, which showed they were keeping up with recommendations from manufacturers.

No information was provided about the person who died, except they were older than 50.

The health unit will release tips for homeowners in the future on how to clean and disinfect household items like shower heads, faucets, humidifiers, and hot tubs to prevent a local exposure. The next update on the outbreak is expected on Monday afternoon, officials said.

The health unit has said there is no “broad risk” to the public in the outbreak, and it is not recommending any changes in behavior.

While sporadic cases of legionnaires’ disease are common, outbreaks are rare. The last one in London, in 2019, sent six people to hospital.

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