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An outbreak of legionnaires’ disease in London has put 10 people, among 20 confirmed cases, in hospital as public health officials continue to track its source.
Patients in hospital are receiving varying degrees of treatment from intravenous antibiotics to being intubated, Joanne Kearon, associate medical officer of health for the Middlesex-London health unit, said Thursday.
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Outbreaks of legionnaires’ disease are rare, the last in London occurring in 2019 that sent six people to hospital, but the rate of hospital admission is typical, she said.
“Many people may have been exposed, but they don’t develop symptoms. If they do become infected, their symptoms are mild. It’s what’s termed Pontiac fever, and so they don’t see a health care provider, they don’t get tested, (and) we never find out about it,” Kearon said.
Legionnaires’s disease is a severe respiratory illness that can cause fever, chills and a dry cough.
The legionella bacteria can grow in warm water sources such as air-conditioning systems, hot water tanks and heaters and plumbing systems.
Transmission occurs when the bacteria is aerosolized by fans or wind and people breathe it in. It cannot be spread between infected people.
The Middlesex-London Health Unit was notified July 24 about a cluster of cases that appeared to be pneumonia. After investigation, the health unit declared an outbreak.
The number of confirmed cases is likely to change, as cases could be found not to be related to the outbreak, or older cases linked to the outbreak come forward, Kearon said. The health unti also can’t be certain whether exposures still are happening, she said.
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“It’s hard to say for certain at this point. The cluster of cases that we have right now, it would still be reasonable to say that the exposures happened in a short time frame,” Kearon said. “It’s whether we continue to see cases ongoing, that would start to point to there being continuing exposure.”
The health unit is continuing to investigate the source of the legionella by sampling warm water systems within a “broad” five to 10 kilometre radius in southeast London and sending samples to Public Health Ontario for testing.
If a source is not identified within the area where the cluster of cases was found, a more broad search will be initiated, taking more time, Kearon said. The health unit might identify colonies that are not relevant to the exposure because the legionella bacteria is common in warm summer months, she said.
It’s also possible the health unit might not find the origin of the outbreak, Kearon said.
In the meantime, the Middlesex-London Health Unit is co-ordiating with operators of warm water sources to make sure they sanitize their systems, and encouraging anyone who has symptoms to see their health care provider.
The health unit says there is no “broad risk” to the public in the outbreak, and it is not recommending any changes to behaviour.
jmoulton@postmedia.com
@jackmoulton65
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