A Legionnaires’ outbreak has been declared by the Middlesex-London Health Unit.
“So far this year in 2025 we have had 43 cases of Legionella confirmed and unfortunately we have had one person die,” said Joanne Kearon, a medical officer of health with the Middlesex-London Health Unit.
The health unit said most of the cases live and or work in a six-kilometer radius of one another.
“Legionella can spread on the wind after it’s been aerosolized and so it is a very large area that we are looking at, about a 5 or 6 km radius of southeast London,” said Kearon. “We do not know yet where the source is.”
Legionella bacteria are naturally found in water sources such as hot tubs, cooling towers, hot water tanks, large plumbing systems, or parts of air-conditioning systems.
People may inhale the bacteria and become unwell.
“This can cause a short self-limited illness called Pontiac fever,” said Kearon. “People get sick for a couple days but then feel better.”
People who are older, have lung problems or are immunocompromised are at greater risk for serious infection.
Legionella is not transmitted from person-to-person.
Symptoms of Legionnaires’
*Symptoms typically develop two to ten days after exposure
- Shortness of breath
- High fever
- Chills
- Dry cough
