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Fact sheet (PDF file)

Notice for Property Managers and Facility Maintenance Operators:

Poorly maintained water systems have recently been linked to outbreaks of illness caused by Legionella bacteria.

Regular maintenance of water systems in accordance with industry standards can prevent outbreaks of disease caused by Legionella bacteria. Click here for more information and guidance to reduce the risk.

What is legionellosis?

  • Legionellosis is a bacterial infection that can cause 2 different illnesses:
    • Legionnaires’ disease is the more severe form of infection which includes pneumonia.
    • Pontiac Fever is a milder influenza-like illness without pneumonia.

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How is legionellosis spread?

  • Legionella bacteria are found in water sources, especially when water is kept at 20 - 43°C (68 - 110°F).
  • People become infected by breathing in mist or vapour containing the bacteria.
  • Single cases of Legionnaires' disease are more common, but outbreaks do occur and have been reported in hospitals, hotels, other large buildings and cruise ships.
  • Outbreaks and individual cases have been traced to a number of specific sources including:
    • Domestic hot and cold water systems, including taps, showers, and toilets
    • Wet cooling systems (cooling towers and evaporative condensers)
    • Whirlpool spas (spa pools/Jacuzzis)
    • Natural spas
    • Humidifiers
    • Respiratory therapy equipment
    • Fountains/sprinkler systems
    • Humidified display cabinets for meat and vegetables
    • Compost, potting soil
  • Legionellosis is not spread from one person to another. You cannot contract Pontiac fever or Legionnaires' disease from an infected person.

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What are the symptoms of legionellosis?

Legionnaires' disease is a type of pneumonia that varies in severity from relatively mild to fatal.

  • Symptoms can include:
    • high fever
    • chills
    • cough
    • fatigue
    • headache
    • aching muscles
    • chest pain
    • loss of appetite.
  • Symptoms usually begin within 2-10 days after exposure.
  • Anyone with symptoms of Legionnaires' disease should seek immediate medical attention.
  • Many cases are treated successfully with antibiotics.

Pontiac fever causes an influenza-like illness.

  • Symptoms include:
    • fever
    • lack of appetite
    • headache
    • aching muscles
  • These symptoms can begin within 1-2 days after exposure.
  • Pontiac fever is not associated with pneumonia.
  • In most cases no treatment is required, and people recover within 2-5 days.

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Who is at risk of getting legionellosis?

  • Anyone can get legionellosis, but the risk of developing the disease is greater for people who are middle aged and older.
  • It is uncommon for people less than 20 years old to get legionellosis.
  • Serious illness and death is more common in:
    • Elderly persons
    • People who smoke
    • Persons with diabetes
    • People with a chronic lung or kidney disease
    • People with weakened immune systems due to conditions such as cancer or an organ transplant
  • People in certain occupations, such as those who do maintenance work on large air-conditioning systems, may be at increased risk for exposure to Legionella bacteria. However, if exposed, an individual's risk of developing a serious infection would depend on the factors listed above.

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How can I minimize my risk?

  • Legionellosis is not a common disease and the risk of getting it is generally quite low.
  • Minimizing your risk in large buildings, such as hotels and hospitals, is difficult because you cannot predict where or when the bacteria will be present. The key to controlling the risk of infection from these sources is a combination of good engineering practices and good infection control policies and guidelines.
  • In your home, you can minimize risks through the proper maintenance of all mist-producing devices such as shower heads, faucets, hot tubs, whirlpools, and humidifiers. Ensure that you clean and disinfect hot tubs, whirlpools, and humidifiers regularly according to the manufacturers' directions.
  • Periodic flushing of unused water lines is recommended to help prevent stagnation.
  • A hot water tank should be set at 60°C(140°F) (please carefully read the caution on scalding).
    • According to the Ontario Building Code, pressure-balanced or thermostatic valves should be used so that the water temperature of all fixtures does not exceed 49°C (120°F).
    • When such valves are not available, to prevent scalding it is recommended to lower the temperature setting of the hot water tank so that the tank itself is at 49°C.
    • The risk of scalding is usually a more important risk than the much smaller risk of the growth of Legionella bacteria, especially for infants, children, elderly, and others who may have difficulty adjusting taps quickly.
  • To check the temperature at the tap and get an idea of the temperature in the hot water tank, run the hot water tap closest to the hot water tank and check the water with a probe-type thermometer.

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