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.
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:
- Chest X-Rays
- Gram Stain
- Acid Fast Bacillus (AFB) Tests
- Bacteria Culture
- Sputum Culture
- Respiratory Pathogens Panel