by Rick Alan
Legionnaires disease is a lung infection. It is a form of pneumonia.
Legionnaires disease is caused by specific bacteria. The bacteria are most often found in sources of standing water. It may be found in cooling towers, HVAC systems, and air conditioners.
The bacteria enters the body through the lungs. It is inhaled in water vapor from a contaminated water source. The infection does not pass from person to person.
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Factors that may increase the chances of Legionnaires disease include:
Symptoms may include:
Your doctor will ask about your symptoms and medical history. A physical exam will be done. A chest x-ray may be done to get images of the lungs. Blood and coughed fluid may also be tested to look for the cause of the infection.
Antibiotics can help to clear the infection.
Proper design, maintenance, and cleaning of high-risk areas can reduce the risk of spreading the disease. This includes any area with standing water.
Centers for Disease Control and Prevention
National Institute of Environmental Health Sciences
Nova Scotia Health Authority
Public Health Agency of Canada
Legionella infections. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T904756/Legionella-infections . Updated October 4, 2019. Accessed October 4, 2019.
Legionella infections. Merck Manual Professional Version website. Available at:
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Updated May 2016. Accessed October 4, 2019.
Legionella (Legionnaires' disease and Pontiac fever). Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/legionella/about/index.html. Updated May 31, 2016. Accessed October 4, 2019.
Last reviewed October 2019 by
EBSCO Medical Review Board
David L. Horn, MD, FACP
Last Updated: 10/4/2019