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Signs and Symptoms

People who get sick after being exposed to Legionella can develop two different illnesses, collectively known as legionellosis: Legionnaires’ disease and Pontiac fever.

Legionnaires' Disease on X-ray

Legionnaires’ Disease

Legionnaires’ disease is very similar to other types of pneumonia (lung infection), with symptoms that include:

  • Cough
  • Shortness of breath
  • Fever
  • Muscle aches
  • Headaches

Legionnaires’ disease can also be associated with other symptoms such as diarrhea, nausea, and confusion. Symptoms usually begin 2 to 14 days after exposure to the bacteria but can take longer.

If you develop pneumonia symptoms, see a doctor right away. Be sure to mention if you may have been exposed to Legionella, have used a hot tub, spent any nights away from home, or stayed in a hospital in the last two weeks.

The image above is an X-ray showing lungs with Legionnaire's disease. Legionnaires' disease often looks similar to a chest X-ray to other types of pneumonia.

Pontiac Fever

Pontiac fever is a milder infection than Legionnaires’ disease. Symptoms are primarily fever and muscle aches. Symptoms can begin a few hours to 3 days after exposure to the bacteria. Symptoms usually last less than a week. Pontiac fever is different from Legionnaires’ disease because someone with Pontiac fever does not have pneumonia.

Page last updated: September 5, 2023