Is Legionnaires’ Disease Fatal?

Medically Reviewed on 6/29/2022
Is Legionnaires' Disease Fatal?
Legionnaires’ disease is a type of lung infection (bacterial pneumonia) caused by Legionella bacterium.

The death rate of Legionnaire’s disease is about 5 to 10 percent in normal individuals and may be as high as 40 to 80 percent in untreated patients who are immunosuppressed. When treated on time, the mortality rate can be reduced to 5 to 30 percent as per World Health Organization’s data.

What is Legionnaires’ disease?

Legionnaires’ disease is a type of lung infection (bacterial pneumonia) caused by Legionella bacterium. It is a severe form of pneumonia caused by breathing in water contaminated by the bacterium that thrives in water.

Legionella usually spreads through water droplets in the air (airborne), but in rare cases, people can get sick after drinking or swallowing contaminated water from freshwater lakes, streams, manmade water structures, natural water, and soil.

Rarely, people can contract Legionnaires’ disease by aspirating drinking water, which occurs when water goes down the trachea into the lungs instead of the esophagus and stomach.

What are the risk factors of Legionnaires’ disease?

Certain people are at an increased risk of Legionnaires' disease including:

How does Legionnaires’ disease spread?

The most common places where people may get exposed to the bacterium include hotels, long-term care facilities, and hospital settings.

Manmade water systems that can spread Legionella include:

  • Hot tubs
  • Shower heads
  • Faucets
  • Humidifiers
  • Decorative water features, such as fountains
  • Hot water tanks and heaters
  • Air conditioning units for large buildings

Most healthy people do not get Legionnaires' disease even after being exposed to the bacterium.

Legionnaires’ disease is not contagious, which means it does not spread from person to person.

What are the symptoms of Legionnaires’ disease?

Most people may show symptoms a few days up to a week after being exposed to the Legionella bacterium.

Similar to other types of pneumonia, symptoms of Legionnaires' disease can include:


What is pneumonia? See Answer

How is Legionnaires’ disease diagnosed?

Legionnaires’ disease is detected the same way other forms of pneumonia are diagnosed, such as:

  • Current symptoms
  • Physical examination
  • Chest X-ray
  • Blood test
  • Urine test
  • Phlegm/sputum/mucus examination
  • Computed tomography scan of the brain
  • Spinal tap (test of spinal fluid)

What other disease is caused by Legionella?

Legionella can cause two different illnesses, collectively known as legionellosis: Legionnaires’ disease and Pontiac fever.

Pontiac fever is characterized by the following:

  • It presents a mild flu-like illness without lower respiratory symptoms such as coughing.
  • It is less severe than Legionnaires’ disease.
  • Symptoms of Pontiac fever usually begin 24 to 72 hours after exposure to the bacterium. 
  • Pontiac fever might go away on its own without any treatment, often within three to five days.

How is Legionnaires’ disease treated?

The doctor can treat Legionnaires’ quickly with medications or antibiotics such as:

What are the complications of Legionnaires’ disease?

Legionnaires’ disease is often effectively treated with antibiotics.

Without early and appropriate treatment, Legionnaires’ disease can cause serious problems including:

Medically Reviewed on 6/29/2022
Image Source: iStock image

Four Key Things You Should Know About Legionnaires’ Disease American Lung Association:

Legionnaires' Disease Cleveland Clinic:

Brunilda Nazario Legionnaire's Disease WebMD:

Legionella Infection Medscape: