Source: Health Canada


Legionellosis is an infection caused by a type of bacteria called Legionella. It is the source of two different conditions: ''Legionnaires'' disease and Pontiac fever. ''Legionnaires'' disease is a form of pneumonia that can lead to an outbreak. Its severity can vary, and is sometimes fatal. Pontiac fever is a mild infection that resembles the flu without pneumonie.


Legionella disease is named after an American legion convention held in Philadelphia in 1976, in which 29 people have died following an outbreak of pneumonia. Scientists later discovered that the bacteria could also cause a less severe infection called Pontiac fever.

Spread of legionella

Legionella bacteria are found in water supplies. They can grow in stagnant water at certain temperatures (between 25°C and 45°C). People become infected by sucking droplets suspended in the air or vapor containing the bacteria. Cases of ''Legionnaires'' disease are often isolated, but outbreaks are still possible and have been reported in hospitals, hotels and other large buildings and aboard cruise ships. We have identified several specific legionella causes for these outbreaks and these isolated cases:

  • Plumbing (water heaters, showers and faucets);
  • Respiratory therapy equipment (in hospitals);
  • Whirlpools and hot tubs;
  • Humidifiers;
  • Cooling towers of large air conditioning systems (eg. In apartment buildings, hotels and hospitals).

Legionella is not spread from person to person. You can not contract legionella disease or Pontiac fever from an infected person.