About Legionellosis (Legionella)

Minnesota Department of Health
Revised 3/2013

Download a print version of this document:
Legionellosis Fact Sheet (PDF: 19KB/1 page)

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 an infection caused by the bacteria Legionella pneumophila, which 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 inhaling the fine spray (aerosols) from water sources containing Legionella bacteria. 
  • Persons can be exposed to these aerosols 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 (95-115oF), such as certain plumbing systems, hot water tanks, cooling towers, large air conditioning systems, and whirlpool spas. 
  • 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, something that is not usually done on persons who present at the hospital with fever and pneumonia.
    • As a result, Legionnaires’ disease often goes undiagnosed.
    • A urine antigen test is the most common type of test used to diagnose Legionnaires’ disease. 
    • This test detects the presence of Legionella antigen in urine. 

How is it treated?

  • Most cases can be successfully treated with antibiotics.  The case fatality rate is generally 5-30%.

Updated Tuesday, 02-Apr-2013 08:46:32 CDT