Public Health

Communicable Disease


Quick Facts

Legionella is shorthand for Legionella pneumophila, which is the name of the bacteria that causes Legionellosis. 

What is Legionellosis?

Legionellosis is an infection caused by Legionella pneumophila bacteria. The disease can cause two (2) different clinical conditions. Both forms can occur in persons of any age, including those who have healthy immune systems:

  • Legionnaire’s disease –severe respiratory illness with pneumonia that may lead to hospitalization or death. Legionnaire’s disease most often affects middle-aged and older persons who smoke or use tobacco containing products, have weakened immune systems or underlying medical conditions.
  • Pontiac fever–a milder respiratory illness without pneumonia.

What are the symptoms of Legionellosis?

Symptoms of Legionellosis include:

  • Fever
  • Chills
  • Lack of energy
  • Cough
  • Muscle aches
  • Headache
  • Loss of appetite
  • Diarrhea and/or vomiting

Symptoms of Pontiac fever usually start about 24 to 72 hours after exposure.

Symptoms of Legionnaire’s disease also include pneumonia and usually start about 2-10 days after exposure. Hospitalization for Legionnaire’s disease is common and may require antibiotic treatment.


How does Legionellosis spread?

Legionellosis infection happens when a person breathes water droplets from the air (i.e., mist or vapor) that contain the Legionella bacteria. The bacteria are NOT spread from one person to another person.

Outbreaks have been linked with exposures to contaminated water towers, evaporative condensers, potable water systems (i.e sinks and showers), whirlpool spas, water faucets, ice machines, showers, humidifiers, and respiratory therapy equipment. Outbreaks have occurred in hospitals, cruise ships, hotels, and other large buildings. Legionella bacteria have also been found worldwide in creeks and ponds and soil along their banks. 

Legionella bacteria are naturally found in freshwater environments but usually not at high enough levels to cause disease. However, warm, still water (90°F-105°F) environments are favorable for reproduction. When contaminated water becomes aerosolized into water droplets and is inhaled in by a person, the bacteria can infect the lungs and cause illness.


Exposure - Who is at Risk for Getting Legionellosis?

Most people exposed to the bacteria do not become ill. If you have reason to believe you were exposed to the bacteria, talk to your doctor or health care provider. Be sure to mention if you have traveled in the last two weeks. You may also contact IU’s Environmental Health & Safety for additional information.

Some individuals have a higher risk of getting sick, those include:

  • Older people (usually 50 years of age or older)
  • Current or former smokers
  • Those with a chronic lung disease (like COPD or emphysema)
  • Those with a weak immune system from diseases like cancer, diabetes, or kidney failure
  • People who take drugs that suppress (weaken) the immune system (like after a transplant operation or chemotherapy)

A person diagnosed with Legionnaires' disease in the workplace is not a threat to others who share office space or other areas with him or her. However, if you believe that your workplace was the source of the person's illness, contact IU’s Environmental Health & Safety

How do I know if I have Legionellosis?

See your health care provider. Lab testing is needed to confirm a diagnosis. Your health care provider may take a sample of lung tissue, urine, or fluid from the lungs to test. Almost all people have been exposed to the bacteria in their lifetime. That is why it is important that lab results are looked at carefully to make sure a recent infection occurred and not a past exposure to the bacteria.


How is Legionellosis treated?

Antibiotics are sometimes used for treatment of Legionnaire’s disease. Sometimes breathing therapy is needed to help people with breathe easier. 

Pontiac fever is a self-limited illness with recovery within one (1) week and does not benefit from antibiotic treatment. 


How is Legionellosis prevented?

From and institutional standpoint, improved design and maintenance of cooling towers and plumbing systems to limit the growth and spread of bacteria are important. Other prevention measures, such as properly maintaining and disinfecting whirlpool tubs, hot tubs and spas, humidifiers, and decorative fountains are also essential. They should be cleaned and run frequently to prevent growth of bacteria.

From a personal standpoint, avoid inhaling water or dunking your head under water when using hot tubs and spas. Avoid using hot tubs, spas, or whirlpool tubs in public places if the water looks dirty or cloudy or if maintenance records are not maintained correctly. Only sterile water should be used in or to clean respiratory equipment i.e., BiPAP, CPAP


Additional Information

IU Protect - Legionella

Center for Disease Control and Prevention – Legionella 

Indiana State Department of Health – Legionella