The symptoms of Legionnaires' disease typically appear 2 to 14 days after exposure to Legionella bacteria and are similar to those of pneumonia. Common symptoms include:
- Cough, which may be dry or produce sputum, sometimes blood-tinged
- High fever
- Chills
- Shortness of breath
- Headache
- Muscle aches
- Chest pain
- Fatigue
- Nausea, vomiting, and diarrhea
- Confusion or other mental changes
Additional symptoms can include loss of appetite, loss of coordination, and in severe cases, complications such as respiratory failure and kidney issues. Gastrointestinal symptoms and neurological symptoms are also common in many cases. The incubation period is generally 2 to 10 days but can extend up to 20 days in rare cases. There is also a milder illness caused by the same bacteria called Pontiac fever, which presents with fever, muscle aches, chills, headache, and fatigue without pneumonia and usually resolves in a few days. Legionnaires' disease can be severe and life-threatening, especially in older adults or people with weakened immune systems.
