About Legionnaires’ Disease

Revised 2/2019

• Download a print version of this document:
  Legionellosis Fact Sheet (PDF)

On this page:
What is Legionnaires’ disease?
What are the symptoms?
How is it spread?
Who is at risk?
How is it diagnosed?
How is it treated?

What is Legionnaires’ disease?

• Legionnaires’ disease is a lung infection caused by the bacteria Legionella pneumophila.
• The bacteria is found in water. 
• Legionnaires’ disease was named for the first recognized outbreak at a 1976 convention of the American Legion in Philadelphia.

What are the symptoms?

• Symptoms include:
  • muscle aches
  • headache
  • fatigue
  • loss of appetite
  • and coughing
• These symptoms are followed by high fever (102-105°F), pneumonia, and occasionally abdominal pain and diarrhea.

How is it spread?

• Legionnaires’ disease is spread by water droplets in the air that contain Legionella bacteria.
• People can get sick if they breathe in water droplets that contain the bacteria. 
• Persons can be exposed to these water droplets in their homes, at work, in hospitals, or in other public places. 
• Legionella organisms are found in many types of water systems and reproduce in high numbers in warm water (95-115°F), such as certain plumbing systems, hot water tanks, cooling towers, large air conditioning systems, and hot tubs. 
• Legionnaires’ disease is not spread from person to person.

Who is at risk?

• Legionnaires’ disease occurs worldwide, especially in persons over 50 years of age.   
• Other risk factors include smoking; male gender; chronic lung disease; suppressed or weakened immune system due to organ transplant, cancer, kidney disease, or AIDS.

How is it diagnosed?

• Diagnosis of Legionnaires’ disease requires testing for Legionella bacteria. This is not often done when someone goes to a clinic or hospital with fever and pneumonia. 
  • As a result, Legionnaires’ disease often goes undiagnosed.
  • A urine test is the most common type of test used to diagnose Legionnaires’ disease.

How is it treated?

• Most cases can be successfully treated with antibiotics.
• However, about 1 out of every 10 people who get sick with Legionnaires’ disease will die.