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

Medical Author: John P. Cunha, DO, FACOEP
Medically Reviewed on 8/19/2021

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 Legionella bacteria. 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:

In severe cases or if the disease is not treated Legionnaires' disease can progress to:

Symptoms of Pontiac fever begin within 2-3 days of exposure, are much milder than Legionnaires' disease, and include fever, chills, and muscle aches. Symptoms usually resolve within a week with no long-term effects.

What Is the Treatment for Legionnaires' Disease and Pontiac Fever?

Legionella bacteria infections may be effectively treated with different classes of antibiotics, which can eradicate the infection. The earlier treatment is started, the lower the risk of serious illness or complications. Depending on the severity, Legionnaires’ disease may require treatment in a hospital with supportive measures such as: 

  • oxygen, 
  • medications to control nausea and vomiting, or 
  • medications to manage pain and fever.

Pontiac fever resolves on its own, and no specific treatment is required.

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