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Legionella Tests

What are Legionella tests?

Legionella is a type of bacteria that can cause a severe form of pneumonia known as Legionnaires' disease. Legionella tests look for these bacteria in urine, sputum, or blood. Legionnaires' disease got its name in 1976 after a group of people attending an American Legion convention became ill with pneumonia.

Legionella bacteria can also cause a milder, flu-like illness called Pontiac fever. Together, Legionnaires' disease and Pontiac fever are known as legionellosis.

Legionella bacteria are found naturally in freshwater environments. But the bacteria can make people sick when it grows and spreads in man-made water systems. These include plumbing systems of large buildings, including hotels, hospitals, nursing homes, and cruise ships. The bacteria may then contaminate water sources, such as hot tubs, fountains, and air-conditioning systems.

Legionellosis infections happen when people breathe in mist or small drops of water that contain the bacteria. The bacteria do not spread from person to person. But a disease outbreak can occur when many people are exposed to the same contaminated water source.

Not everyone who is exposed to Legionella bacteria will get sick. You are more likely to develop an infection you are:

  • Over the age of 50
  • A current or former smoker
  • Have a chronic disease such as diabetes or kidney failure
  • Have a weakened immune system due to a disease such as HIV/AIDS or cancer, or are taking medicines that suppress the immune system

While Pontiac fever usually clears up on its own, Legionnaires' disease can be fatal if not treated. Most people will recover if promptly treated with antibiotics.

Other names: Legionnaires' disease testing, Legionellosis testing

What are they used for?

Legionella tests are used to find out whether you have Legionnaires' disease. Other lung diseases have symptoms similar to Legionnaires' disease. Getting the right diagnosis and treatment may help prevent life-threatening complications.

Why do I need a Legionella test?

You may need this test if you have symptoms of Legionnaires' disease. Symptoms usually show up two to 10 days after exposure to Legionella bacteria and may include:

What happens during a Legionella test?

Legionella tests may be done in urine, sputum, or blood.

During a urine test:

You will need to use the "clean catch" method to ensure your sample is sterile. The clean catch method includes the following steps:

  • Wash your hands.
  • Clean your genital area with a cleansing pad.
  • Start to urinate into the toilet.
  • Move the collection container under your urine stream.
  • Collect at least an ounce or two of urine into the container, which should have markings to indicate the amount.
  • Finish urinating into the toilet.
  • Return the sample container as instructed by your health care provider.

Sputum is a thick type of mucus made in your lungs when you have an infection.

During a sputum test:

  • A health care provider will ask you to breathe deeply and then cough deeply into a special cup.
  • Your provider may tap you on the chest to help loosen sputum from your lungs.
  • If you have trouble coughing up enough sputum, your provider may ask you to breathe in a salty mist that can help you cough more deeply.

During a blood test:

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don't need any special preparations for a Legionella test.

Are there any risks to the test?

There is no risk to providing a urine or sputum sample. There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

If your results were positive, it probably means you have Legionnaires' disease. If your results were negative, it may mean you have a different type of infection. It may also mean not enough Legionella bacteria were found in your sample.

If you have questions about your results, talk to your health care provider.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about Legionella tests?

Whether your results were positive or negative, your provider may do others tests to confirm or rule out a diagnosis of Legionnaires' disease. These include:

References

  1. American Lung Association [Internet]. Chicago: American Lung Association; c2020. Learn About Legionnaires' Disease; [cited 2020 Jun 4]; [about 4 screens]. Available from: https://www.lung.org/lung-health-diseases/lung-disease-lookup/legionnaires-disease/learn-about-legionnaires-disease
  2. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Legionella (Legionnaires' Disease and Pontiac Fever): Causes, How it Spreads, and People at Increased Risk; [cited 2020 Jun 4]; [about 3 screens]. Available from: https://www.cdc.gov/legionella/about/causes-transmission.html
  3. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Legionella (Legionnaires' Disease and Pontiac Fever): Diagnosis, Treatment and Complications; [cited 2020 Jun 4]; [about 5 screens]. Available from: https://www.cdc.gov/legionella/about/diagnosis.html
  4. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Legionella (Legionnaires' Disease and Pontiac Fever): Signs and Symptoms; [cited 2020 Jun 4]; [about 4 screens]. Available from: https://www.cdc.gov/legionella/about/signs-symptoms.html
  5. Cleveland Clinic [Internet]. Cleveland (OH): Cleveland Clinic; c2020. Clean Catch Urine Collection Instructions; [cited 2020 Jun 4]; [about 5 screens]. Available from: https://clevelandcliniclabs.com/wp-content/assets/pdfs/forms/clean-catch-urine-collection-instructions.pdf
  6. Cleveland Clinic [Internet]. Cleveland (OH): Cleveland Clinic; c2020. Legionnaires' Disease: Diagnosis and Tests; [cited 2020 Jun 4]; [about 4 screens]. Available from: https://my.clevelandclinic.org/health/diseases/17750-legionnaires-disease/diagnosis-and-tests
  7. Cleveland Clinic [Internet]. Cleveland (OH): Cleveland Clinic; c2020. Legionnaires' Disease: Overview; [cited 2020 Jun 4]; [about 3 screens]. Available from: https://my.clevelandclinic.org/health/diseases/17750-legionnaires-disease
  8. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2020. Legionella Testing; [updated 2019 Dec 31; cited 2020 Jun 4]; [about 2 screens]. Available from: https://labtestsonline.org/tests/legionella-testing
  9. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2020. Sputum Culture, Bacterial; [updated 2020 Jan 14; cited 2020 Jun 4]; [about 2 screens]. Available from: https://labtestsonline.org/tests/sputum-culture-bacterial
  10. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2020. Legionnaires' Disease: Diagnosis and treatment; 2019 Sep 17 [cited 2020 Jun 4]; [about 4 screens]. Available from: https://www.mayoclinic.org/diseases-conditions/legionnaires-disease/diagnosis-treatment/drc-20351753
  11. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2020. Legionnaires' Disease: Symptoms and causes; 2019 Sep 17 [cited 2020 Jun 4]; [about 3 screens]. Available from: https://www.mayoclinic.org/diseases-conditions/legionnaires-disease/symptoms-causes/syc-20351747
  12. National Center for Advancing Translational Sciences/Genetic and Rare Diseases Information Center [Internet]. Gaithersburg (MD): U.S. Department of Health and Human Services; Legionnaires' disease; [updated 2018 Jul 19; cited 2020 Jun 4]; [about 3 screens]. Available from: https://rarediseases.info.nih.gov/diseases/6876/legionnaires-disease
  13. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2020. Health Encyclopedia: Sputum Culture; [cited 2020 Jun 8]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=sputum_culture
  14. UF Health: University of Florida Health [Internet]. Gainesville (FL): University of Florida Health; c2020. Legionnaire disease: Overview; [updated 2020 Jun 4; cited 2020 Jun 4]; [about 2 screens]. Available from: https://ufhealth.org/legionnaire-disease
  15. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2020. Health Encyclopedia: Legionella Antibody; [cited 2020 Jun 4]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=legionella_antibody
  16. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2020. Health Information: Legionnaires' Disease and Pontiac Fever: Topic Overview; [updated 2020 Jan 26; cited 2020 Jun 4]; [about 2 screens]. Available from: https://www.uwhealth.org/health/topic/special/legionnaires-disease-and-pontiac-fever/ug2994.html
  17. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2020. Health Information: Sputum Culture: How It Is Done; [updated 2020 Jan 26; cited 2020 Jun 4]; [about 5 screens]. Available from: https://www.uwhealth.org/health/topic/medicaltest/sputum-culture/hw5693.html#hw5711

The medical information provided is for informational purposes only, and is not to be used as a substitute for professional medical advice, diagnosis or treatment. Please contact your health care provider with questions you may have regarding medical conditions or the interpretation of test results.

In the event of a medical emergency, call 911 immediately.