All About Legionnaires' Disease

What You Should About This New Type Of Bacterial Pneumonia

Legionella Pneumophila Bacteria
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Legionnaires’ (LEE-juh-nares) disease is a bacterial infection caused by Legionella pneumophila (LEE-juh-nell-a), a type of bacterium. It was named after an outbreak that occurred in 1976 during an American Legion convention in Philadelphia, Pennsylvania. It is a new type of pneumonia that became known as Legionnaires’ disease. A milder form of the disease, also caused by the Legionella bacterium, is known as Pontiac fever.

Legionellosis (LEE-juh-nuh-low-sis) may be used interchangeably to refer to either Legionnaires’ disease or Pontiac fever.

If the Legionella bacteria infect the lungs causing pneumonia, it is known as Legionnaires’ disease. If the infection is less severe and the symptoms are more flu-like, it is Pontiac fever.

Causes of Legionnaires’ Disease

Legionella is found, naturally, in warm, aquatic environments and is resistant to the effects of chlorine and heat. It is most likely to be found in the following:

  • Hot water tanks
  • Air-conditioning units for large buildings
  • Large plumbing systems
  • Hot tubs
  • Decorative fountains

Legionnaires’ disease is commonly associated with warm water sources and aerosols in a water-base. Legionella is not spread from one person to another and is not contagious. If you are exposed to Legionella that does not mean you will become ill. But if you think you were exposed to the bacteria you should talk to your doctor or your local health department.

Symptoms of Legionnaires’ Disease

The symptoms you experience with Legionnaires’ disease are similar to those of other types of pneumonia. It even looks the same on a chest X-ray. In order to diagnose Legionnaires’ disease, special tests will need to be performed.

Common symptoms of Legionnaires ’ disease include the following:

  • Cough
  • Shortness of breath
  • High fever
  • Muscle ache
  • Headache

Symptoms usually appear 2 to 10 days after exposure to the bacteria but can take up to two weeks for symptoms to appear.

Risk Factors for Legionnaires’ Disease

People most a risk of developing Legionnaires’ disease include people 65 years of age and older, smokers, and those who have a chronic lung disease, such as emphysema. People who have a weakened immune system with conditions such as cancer, diabetes, kidney failure are also more likely to get sick if exposed to the bacteria.

Diagnosis, Treatment, and Prevention

You will most likely have a chest X-ray and a physical examination to confirm the diagnosis of pneumonia. Further testing will include a sputum sample or lung biopsy to accurately diagnose the cause.

Treatment of Legionnaires’ disease requires treatment with antibiotics, most likely in a hospital setting. Without treatment, complications of Legionnaires’ disease can lead to lung failure and death.

If you have a hot tub or decorative fountain you need to maintain the water supply system to prevent the growth of the Legionella bacterium.

Air-conditioning units and hot water tanks also need to be maintained to prevent the bacteria from growing.

You can reduce your risk of developing Legionnaires’ disease by avoiding exposure to areas of high-risk, including hot tubs. If you have a hot tub, make sure that it is properly disinfected and that the pH levels are accurate.


  • Occupational Safety & Health Administration
  • Centers for Disease Control and Prevention
  • Mayo Clinic
  • MedlinePlus

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