London’s legionnaires’ disease outbreak lingers on as another person dies

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A second person has died in an outbreak of legionnaires’ disease in London that was declared in July and investigators still haven’t found the source of the bacteria that has sent 30 people to hospital, the Middlesex-London Health Unit says.

In its first update on the outbreak since Aug. 7, the health unit said five more people have been infected, bringing the total to 30, and one more person has died. The first death was reported Aug. 2

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Every person infected with the disease required hospital treatment and nine were admitted to the intensive-care unit, the health unit said. The people infected with the legionella bacteria were between 37 and 76 years of age, and 19 were male.

“It is an awful situation, and I recognize that,” Joanne Kearon, acting medical officer of health for the Middlesex-London Health Unit, said Friday.

Many people with Legionnaires’ disease may have mild symptoms and never get tested, she said but people with confirmed cases had other conditions that made them more vulnerable to severe symptoms.

Legionnaires’ disease is a severe respiratory illness that can cause fever, chills and a dry cough.

Legionella bacteria can be found in warm water sources such as air-conditioning systems, hot water tanks and heaters and plumbing systems.

Though not considered contagious in person-to-person transmission, legionnaires’ disease can be spread when the bacteria is aerosolized by fans or wind and people breathe it in.

Those most at risk are older, have lung problems or are immune-compromised. 

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Despite the testing of 17 cooling tower sites close to the geographic centre of the cases in southeast London, no samples have turned up a match to the bacteria identified in the confirmed cases. Cooling towers are a water-cooling device used in HVAC and industrial systems.

Officials have repeatedly warned that the source of the outbreak may never be found, but the health unit said Friday transmission is slowing and the outbreak may soon be declared over. But the investigation will continue, whether the outbreak is officially ongoing or not, Kearon said.

“We are still doing environmental testing to try to determine a source,” she said. “It’s uncommon, but these outbreaks do happen, and in 50 per cent of cases of these outbreaks, a source is not found, but that does not mean that the outbreak won’t end.”

Local officials were notified on July 24 about a cluster of cases that first appeared to be pneumonia. Two days later, officials declared an outbreak of legionella. Investigators focused on a five- to 10-kilometre radius in southeast London, but did not specify where.

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The last legionnaires’ disease outbreak in London, in 2019, sent six people to hospital.

The bacteria itself is naturally occurring, and the Middlesex-London Health Unit investigates and tests all cases to find any exposure. With the investigation into this particular outbreak, the focus remains on a five- to six-kilometre radius in southeast London, Kearon said.

“It has shifted as new cases come in, and they tell us about their exposures, we add that information into our analysis, and so potentially we will start moving in one direction,” she said.

Kearon said sites that bacteria samples have been taken from have been sanitized so the source of the outbreak may have already been addressed.

She recommends home and business owners continue to clean and disinfect warm water systems that could harbour the bacteria, but said residents don’t have to adjust their routines or avoid any areas.

To learn more about how to prevent the disease, click here.

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