IAMAT |International Association of Medical Assistance to Travellers| IAMAT |International Association of Medical Assistance to Travellers|

Legionnaires' Disease

Photo By: Kerry Luker

Legionnaires' Disease, also known as Legionellosis, is a lung infection caused by bacteria belonging to the genus Legionella. The majority of infections are caused by the Legionella pneumophila bacterium which is commonly found in outdoor freshwater bodies, soil, and indoor environments with air conditioning, hot water systems, humidifiers, and hot tubs. The bacteria thrive in temperatures between 20° - 50°C / 68° - 122°F and are transmitted by inhaling contaminated water or soil droplets. There is no evidence that Legionellosis spreads from person to person.


The bacteria are present worldwide. Risk occurs when staying in buildings or cruise ships that do not maintain air conditioning systems, humidifiers, whirlpools, or hot tubs properly. Travellers with pre-existing health conditions or a weakened immune system are at higher risk.


The pneumonic form of the illness is characterized by fever, headache, malaise, lethargy, loss of appetite, cough, and phlegm. It can progress into pneumonia, respiratory failure, shock or multi-organ failure, and can be fatal. Treatment includes taking antibiotics for weeks or months. Seek medical care if you exhibit flu-like symptoms for up to 14 days and believe you may have contracted Legionnaires' Disease.

The non-pneumonic illness – also known as Pontiac Fever – includes flu-like symptoms such as fever, headache, malaise, chills, and muscle pain. A person can get ill within 48 hours of being infected and usually heals from this acute infection in 2 to 5 days by treating the symptoms.


There is no preventive vaccine or medication against Legionnaires' Disease.

Information last updated: January 2020