Legionnaires' Disease - Fact Sheet
What is Legionnaires' disease?
Legionnaires' disease (or Legionellosis) is a type of pneumonia that is caused by the bacterium Legionella.
Where are the bacteria found?
Legionella bacteria are found in the environment, usually in water. The bacteria grow best in warm water and have been found in cooling towers, hot tubs, hot water tanks, large plumbing systems and decorative fountains.
How is it spread?
People get sick when they breathe in contaminated water vapor. Legionella bacteria are not spread from person to person. Legionellosis is not contagious.
Who is at risk for infection?
People over the age of 50 years are generally at higher risk of infection. Also, current or former smokers, those with chronic lung disease, weakened immune systems, and those taking immunosuppressant drugs are also at a higher risk.
What are the symptoms of Legionnaires' disease?
Symptoms resemble those of other types of pneumonia and can include cough, high fever (102-105F), shortness of breath, muscle aches and headaches. Some people will have diarrhea. Symptoms usually begin 2-10 days after exposure to the bacteria.
What should you do if I think you have been exposed to Legionella?
Most people exposed to Legionella do not have symptoms. If you have respiratory symptoms, and believe you may have pneumonia, seek medical attention right away. This is especially important if you have a medical condition that affects your breathing. A milder infection to Legionella exposure is called Pontiac Fever. The symptoms are similar to those of Legionnaires' disease; however, you will not have pneumonia and symptoms will last approximately 2-5 days.
How is Legionnaires' disease diagnosed?
Most people infected with Legionnaires' disease have pneumonia that can be seen in a chest x-ray. Other tests include urine antigen test, culture, and blood specimen. If a patient has a confirmed x-ray and a positive test result from a urine sample, the patient is diagnosed with Legionnaires' disease. Also, if a culture from sputum, lung biopsy or other site is positive, or two blood tests taken within several weeks of each other show a four-fold rise in antibody levels, the patient is diagnosed with Legionnaires' disease.
What is the treatment for Legionnaires' disease?
Most people infected with Legionnaires' disease are successfully treated with antibiotics, although hospitalization may be necessary. Some people may have severe complications or die from the infection. Pontiac Fever will eventually go away without treatment, antibiotics are not necessary.
This fact sheet is for informational purposes only. It should not be used for self-diagnosis or as a substitute for consultation with a health care provider. If you think that you may have this infection, or have questions about the disease described above, you should consult your health care provider.

For additional information on this disease, visit the Centers or Disease Control and Prevention website.

To contact the Epidemiology and Emerging Infections Program, please call 860-509-7994.