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Symptoms and Signs of Legionnaires' Disease and Pontiac Fever (Legionellosis)

Doctor's Notes on Legionnaires' Disease and Pontiac Fever (Legionellosis)

Legionnaires' disease is a serious illness caused by Legionella bacteria that can result in fatal cases of pneumonia. Pontiac fever is a self-limited, flu-like illness, also caused by the Legionellabacteria. Legionellosis refers to the two illnesses caused by the bacteria of the genus Legionella (Legionnaires' disease and Pontiac fever).

Early symptoms of Legionnaires' disease include headache, muscle pains, fever, and chills. After a day or two, symptoms worsen and may include cough and shortness of breath (which worsens as the pneumonia progresses), gastrointestinal symptoms (nausea, vomiting, and diarrhea), confusion, chest pain, and body aches. In severe cases or if the disease is not treated Legionnaires' disease can progress to respiratory failure, renal failure, and death. Symptoms of Pontiac fever begin within two to three days of exposure and are much milder than in Legionnaires' disease and include fever, chills, and muscle aches. Symptoms usually resolve within a week with no long-term effects.

Medical Author: John P. Cunha, DO, FACOEP
Medically Reviewed on 3/11/2019


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.