Legionellosis (Legionella, Legionnaires Disease)

Legionellosis is caused by Legionella bacteria that is naturally present in water sources and can multiply in poorly maintained man-made water systems like cooling towers, hot tubs, sprinkler systems, humidifiers, decorative fountains, etc. Infection occurs when individuals breathe in small aerosolized droplets containing the bacteria. Legionella bacteria are not spread from person-to-person.

Infection can range in severity ranging from mild, flu-like symptoms (Pontiac fever) to more serious lung infection or pneumonia (Legionnaires disease), which could require hospitalization and may be fatal.

In Ontario, legionellosis most often affects men and adults over the age of 60. People at higher risk include those who smoke, have lung or kidney disease, diabetes, weakened immune systems, drink heavily, or work around large building water systems like cooling towers.