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Legionnaires' Disease

What is Legionnaires’ Disease?
Legionnaires' disease is caused by a type of bacteria called Legionella. The Legionella bacteria are found naturally in the environment, usually in water. The bacteria grows best in warm water, like the kind found in

  • Hot tubs
  • Cooling towers
  • Hot water tanks
  • Large plumbing systems
  • Decorative fountains

Each year, between 8,000 and 18,000 people are hospitalized with Legionnaires' disease in the U.S. However, many infections are not diagnosed or reported, so the number of infections may be higher. More illness is usually found in the summer and early fall, but it can happen any time of year.

What are the signs and symptoms of Legionnaires’ disease?
Legionnaires' disease can have symptoms like many other forms of pneumonia, so it can be hard to diagnose at first. Signs of Legionnaires' disease can include:

  • Cough
  • Shortness of breath
  • High fever
  • Muscle aches
  • Headaches

These symptoms usually begin 2 to 14 days after being exposed to the bacteria. A milder infection, also caused by Legionella bacteria, is called Pontiac fever. The symptoms of Pontiac fever are similar to those of Legionnaires’ disease and usually last for 2 to 5 days. Pontiac fever is different from Legionnaires' disease because the patient does not have pneumonia. Symptoms go away on their own without treatment.

How does Legionnaires’ disease spread?
People get Legionnaires' disease when they breathe in a mist or vapor (small droplets of water in the air) containing the bacteria. One example might be from breathing in droplets sprayed from a hot tub that has not been properly cleaned and disinfected. The bacteria are not spread from one person to another person.

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 local health department. Be sure to mention if you have traveled in the last two weeks.

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 your local health department.

Is Legionnaires’ disease treatable?
Legionnaires' disease requires treatment with antibiotics (drugs that kill bacteria in the body), and most cases of Legionnaires’ disease can be treated successfully with antibiotics. Healthy people usually get better after being sick with Legionnaires’ disease, but hospitalization is often required. Pontiac fever goes away without specific treatment. Antibiotics provide no benefit for a patient with Pontiac fever.

How is Legionnaires’ disease diagnosed?
Most people with Legionnaires' disease will have pneumonia (lung infection) since the
Legionella bacteria grow and thrive in the lungs. Pneumonia is confirmed either by chest x-ray
or on physical exam. The Legionnaires’ bacteria can be diagnosed using a urine antigen test;
or the bacteria can be cultured from sputum or a lung biopsy; or it can be diagnosed through
blood specimens.

Who is at risk for Legionnaires’ disease?
Most healthy individuals do not become infected with Legionella bacteria after exposure. People at higher risk of getting sick are:

  • 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)

How can I prevent being exposed to Legionnaires’ disease?
The key to preventing legionellosis is maintenance of the water systems in which Legionella bacteria grow, including drinking water systems, hot tubs, decorative fountains, and cooling towers. Persons at increased risk of infection may choose to avoid high-risk exposures, such as being in or near a hot tub.