Legionnaires Disease



Legionnaires disease is caused by a type of bacteria found in sources of standing water, such as cooling towers, HVAC systems, and air conditioners.

The bacteria is inhaled in water vapor from a contaminated water source. From there, it enters the lungs. The infection does not pass from person to person.

The Lungs
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Risk Factors

Legionnaires disease is more common in people over 50 years of age. Other things that raise the risk are:

  • A weak immune system
  • Exposure to contaminated water
  • Smoking
  • Long term lung disease
  • Kidney failure
  • Diabetes



Symptoms may include:

  • Tiredness
  • Fever (often high)
  • Chills and muscle aches
  • Cough
  • Headache
  • Nausea and vomiting
  • Loose stools


The doctor will ask about symptoms and past health. A physical exam will be done. Urine, blood, and coughed fluid may also be tested. A chest x-ray may be done to get pictures of the lungs. Tests will confirm the diagnosis.



Legionnaires disease is treated with antibiotics to clear the infection.


Proper water management can lower the risk of infection.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.