About the Disease

Legionnaires' disease is a severe, often lethal, form of pneumonia. It's caused by the bacterium Legionella pneumophila found in both potable and nonpotable water systems. Each year, an estimated 10,000 to 18,000 people are infected with the Legionella bacteria in the United States.

It is not uncommon for patients with Legionnaires' disease to be admitted to the intensive care unit. Some will suffer long-term impaired health-related quality of life.  A study of outbreak survivors showed persistence of fatigue (75%), neurologic symptoms (66%) and neuromuscular symptoms (63%) in months after an outbreak. See Share Your Story for a first-hand account of the severity of this disease.

What are the symptoms of Legionnaires' disease?

The incubation period of Legionnaires' disease is from two to ten days; this is the time it takes before symptoms of the illness appear after being exposed to the bacteria. For several days, the patient may feel tired and weak. Most patients who are admitted to the hospital develop a high fever, often greater than 39.5°C (103°F). A cough can be the first sign of a lung infection. The cough may be sufficiently severe to cause sputum production (coughed up mucous). Gastrointestinal stomach symptoms are common with diarrhea being the most distinctive symptom. Many patients have nausea, vomiting, and stomach discomfort. Other common symptoms include headaches, muscle aches, chest pain, and shortness of breath.