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Infectious Diseases


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What is legionellosis?

Legionellosis is a respiratory disease caused by the bacterium Legionella pneumophila. This bacterium is responsible for two distinct illnesses. Legionellosis is a more serious illness and Pontiac fever is milder. Most healthy people exposed to Legionella do not get sick.  For those infected, the severity of the illness varies.  There is about a 10% case fatality rate.

Legionella bacteria are found naturally in the environment. They are usually in water, including hot water tanks, air conditioning cooling towers, humidifiers, whirlpools, spas, hot tubs and decorative fountains.

How is legionellosis spread?

You may be exposed to Legionella bacteria if you breathe in small droplets of water in the air that have been contaminated with the bacteria. The bacteria are not spread from person-to-person. You cannot become infected by drinking water containing Legionella bacteria.

Who is at risk?

People over 50 years of age, heavy drinkers, those whose immune system is impaired due to other medical conditions, smokers and people who have a chronic lung disease, such as emphysema, are at greater risk of developing Legionellosis.

What symptoms should I watch for?

Symptoms of Legionellosis can include a high fever, chills, cough, muscle aches and headache. Some individuals may also suffer from abdominal pain and diarrhea. In severe cases respiratory failure and death can occur. Symptoms of Legionellosis usually develop within 2 to 10 days following exposure to the bacteria.

Pontiac fever is the milder form of illness and symptoms include fever and muscle aches without pneumonia. Symptoms of Pontiac fever usually develop 1 to 2 days following exposure and most individuals recover completely without treatment.

What is the treatment for Legionellosis?

Consulting your health care provider is recommended as he/she may suggest laboratory testing or/and antibiotic treatment.

How do I protect myself and others?

  • In your home, you can minimize risks through proper maintenance of all mist-producing devices, such as shower heads, hot tubs, whirlpools and humidifiers. Ensure you clean and disinfect these devices regularly according to the manufacturers’ directions.
  • Cooling towers, humidifiers, air handling units, floor drains and other sources of stagnant water should be inspected, cleaned and disinfected. Appropriate chemical substances should be used to limit the growth of slime-forming organisms.
  • Cooling towers should be drained when not in use.
  • Cooling towers should be mechanically cleaned periodically to remove scale and sediment.
  • Develop a schedule for removing, cleaning and disinfecting shower heads and all equipment that generates water droplets.
  • Ventilation intakes should be checked to ensure proper sealing of filters.
  • Only distilled water should be used in respiratory devices; the devices should be cleaned on a regular basis.
  • Maintaining hot water system temperatures at 50 C or higher may reduce the risk of transmission.

Is there anything special I need to know?

If you have been exposed to a known source of Legionella bacteria and develop symptoms of Legionellosis seek immediate medical attention and inform your health care provider of your exposure.

For data on the incidence of Legionellosis in Simcoe Muskoka and Ontario, please visit the Legionellosis page on the health unit’s HealthSTATS site

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