09-07-2025
Legionnaires' disease is spreading in London, Ont. What to know about the illness after 1 person dies, dozens gets sick from an outbreak
Legionnaires' disease has caused one person to die and more than 40 to get sick in London, Ont., according to public health officials. Most of the cases were reported over the last week, the Middlesex-London Health Unit noted, which declared the outbreak on Tuesday.
The health unit said it's working closely with Public Health Ontario and Public Health Ontario Laboratories to investigate and find the source of the outbreak. It added most of the cases are from people living or working within a six-kilometre radius of one another in the southeastern end of the city.
Dr. Joanne Kearon, the health unit's associate medical officer of health, told the CBC she understands many people are anxious to know where the disease is coming from, but that "unfortunately, we don't have a location yet."
There have been a total of 43 cases reported to the health unit so far for 2025, with a few cases per month being a normal occurrence. But officials declared an outbreak when there were more than 30 cases reported last week. According to Kearon, a spike is understandable amid the warm weather the city has recently seen.
The City of London experienced a legionnaires' disease outbreak last summer, where two people died and 30 infections were reported. Back then, most of the cases were found in the city's east end.
"At this time, it is not known whether [the current outbreak] is the same location as the legionnella outbreak from last year," the health unit said. "However, this is being considered as part of the ongoing investigation."
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Contact a qualified medical professional before engaging in any physical activity, or making any changes to your diet, medication or lifestyle.
Legionnaires' disease is a serious respiratory illness that can result in pneumonia. It's one of two illnesses caused by the Legionella bacteria, which can also cause Pontiac fever, a milder condition that's similar to the flu and typically goes away on its own. Untreated legionnaires' disease, on the other hand, can be fatal.
According to the Public Health Agency of Canada, leggionaires' disease is named after a 1976 pneumonia outbreak in Philadelphia, where 29 people died at an American Legion Convention late that summer.
Symptoms of legionnaires' disease typically appear around two to 10 days after contact with the bacteria, according to Mayo Clinic. Some of the initial signs include headache, muscle aches and a fever higher than 104⁰F/40⁰C. Over the span of a few days, symptoms can include:
Cough, which may bring up mucus and sometimes blood
Shortness of breath
Chest Pain
Nausea, vomiting and diarrhea
Confusion and other mental changes
Most cases of legionnaires' disease are caused the bacterium Legionella pneumophila, which lives in soil and water. Legionella can be found naturally in lakes and streams, but it can also contaminate drinking water and water systems — like air conditioners — in large buildings.
While it's possible for cases to occur at home, it's more likely for outbreaks to originate in larger buildings. That's probably because the bacteria can grow and spread more easily in large systems, according to Mayo Clinic. Moreover, air conditioning systems in homes and vehicles typically don't use water to work.
Typically, someone will inhale mist or water that's contaminated with Legionella bacteria. This might be from the spray off a shower or hot tub, or it could be from water from the cooling system in large buildings. You might see outbreaks from hospitals, hotels, cruise ships, long-term care homes or other locations that have the following:
Hot tubs
Shower heads
Faucets
Humidifiers
Decorative water features like fountains
Heating and cooling systems
Soil
Generally, legionnaires' disease isn't contagious. That means it can't be spread from person to person.
While cases that begin at home are rare, you can prevent infections by ensuring all of your shower heads, faucets, hot tubs and humidifiers are properly cleaned. In larger buildings, owners and property managers should upkeep their water systems.
Amid the outbreak in Ontario, the Middlesex-London Health Unit has asked all business owners and property managers to make sure their cooling equipment is regularly maintained and sanitized according to manufacturer guidelines. "This is the best way to reduce the risk of further legionella outbreaks," the health unit added.
If you're healthy, you most likely won't get sick if you come into contact with Legionella bacteria. The following people are more likely to become ill:
Current or former smokers
People with weakened immune systems
Those with chronic lung disease or other conditions like diabetes, kidney disease or cancer
Anyone age 50 or older
Diagnosing and treating legionnaires' disease can shorten the time it takes to recover and prevent serious ailments. People at high risk need treatment right away.
Legionnaires' disease is treated with antibiotics, which you'll likely get either through an IV or by pill form. You'll probably also need to remain hospitalized whilst being treated. In some cases, you may get treatment for oxygen if you're having difficulty breathing.
After leaving the hospital, you may still need to take medication to ensure the infection goes away completely. Ongoing symptoms may include fatigue, muscle aches, slurred speech and trouble walking.
Luckily, most people survive legionnaires' disease. According to Cleveland Clinic, lung infections due to Legionella are only fatal around five to 10 per cent of the time. If left untreated, however, fatality rates rise to 30 to 80 per cent.
