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What is Legionnaires' Disease?


Legionnaires’ (LEE-juh-nares) disease is a serious type of pneumonia (lung infection) caused by Legionella (LEE-juh-nell-a) bacteria. People can get sick when they breathe in mist or accidently swallow water into the lungs containing Legionella.

​​What is Pontiac Fever?

Pontiac fever is milder than Legionnaires' disease and presents as an influenzalike illness, with fever, headache, and muscle aches, but no signs of pneumonia. Pontiac fever can affect healthy people, as well as those with underlying illnesses, and symptoms occur within 72 hours of exposure.

Causes and Common Sources of Infection


Legionella is a type of bacterium found naturally in freshwater environments, like lakes and streams. It can become a health concern when it grows and spreads in human-made building water systems like:

  • Showerheads and sink faucets

  • Cooling towers (structures that contain water and a fan as part of centralized air cooling systems for building or industrial processes)

  • Hot tubs that aren’t drained after each use

  • Decorative fountains and water features

  • Hot water tanks and heaters

  • Large plumbing systems


Home and car air-conditioning units do not use water to cool the air, so they are not a risk for Legionella growth.

How It Spreads


After Legionella grows and multiplies in a building water system, water containing Legionella then has to spread in droplets small enough for people to breathe in. People can get Legionnaires’ disease or Pontiac fever when they breathe in small droplets of water in the air that contain the bacteria.

Less commonly, people can get sick by aspiration of drinking water containing Legionella. This happens when water accidently goes into the lungs while drinking. People at increased risk of aspiration include those with swallowing difficulties.

In general, people do not spread Legionnaires’ disease and Pontiac fever to other people. However, this may be possible under rare circumstances.

Talk to your doctor or local health department if:

  • You believe you were exposed to Legionella

  • You develop symptoms, such as fever, cough, chills, or muscle aches


People at Increased Risk


Most healthy people exposed to Legionella do not get sick. People at increased risk of getting sick are:

  • People 50 years or older

  • Current or former smokers

  • People with a chronic lung disease (like chronic obstructive pulmonary disease or emphysema)

  • People with weak immune systems or who take drugs that weaken the immune system (like after a transplant operation or chemotherapy)

  • People with cancer

  • People with underlying illnesses such as diabetes, kidney failure, or liver failure


Overview of Water Management Programs


Water management programs identify hazardous conditions and take steps to minimize the growth and transmission of Legionella and other waterborne pathogens in building water systems. Developing and maintaining a water management program is a multi-step process that requires continuous review. Such programs are now an industry standard for large buildings in the United States.

Please contact DET for more information regarding our Legionella consulting services.



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