Learn More About Legionnaires' Disease

Click here for comprehensive information on Legionnaires' Disease from the Centers for Disease Control.

Click here for more information on Legionnaires' Disease from the U.S. Department of Labor's Occupational Safety and Health Administration.

Click here for comprehensive information on Legionnaires' Disease from National Institute of Environmental Health Services.

Source: Centers for Disease Control

Legionellosis is an infection caused by the bacterium Legionella pneumophila.

It has two forms. Legionnaires' disease is most severe. Pontiac fever is a milder illness.

Legionnaires' disease acquired its name in 1976 when an outbreak of pneumonia occurred among persons attending a convention of the American Legion in Philadelphia. Later, the bacterium causing the illness was named Legionella.

An estimated 8,000 to 18,000 people get Legionnaires' disease in the United States each year. Some people can be infected with the Legionella bacterium and have mild symptoms or no illness at all.

About 5% to 30% of people who have Legionnaires' disease die.

Patients with Legionnaires' disease usually have fever, chills, and a cough, which may be dry or may produce sputum. Some patients also have muscle aches, headache, tiredness, loss of appetite, and, occasionally, diarrhea. Laboratory tests may show that these patients' kidneys are not functioning properly. Chest X-rays often show pneumonia.

It is difficult to distinguish Legionnaires' disease from other types of pneumonia by symptoms alone; other tests are required for diagnosis.

Persons with Pontiac fever experience fever and muscle aches and do not have pneumonia. They generally recover in 2 to 5 days without treatment.

The time between the patient's exposure to the bacterium and the onset of illness for Legionnaires' disease is 2 to 10 days; for Pontiac fever, it is shorter, generally a few hours to 2 days.

Source: Centers for Disease Control