What are Legionella tests?

Legionella is a type of bacteria. When it affects your lungs, it can cause a severe form of pneumonia known as Legionnaires' disease. Legionella tests look for these bacteria in urine or sputum. A blood test may be done to check if you have been exposed to the bacteria, but it cannot diagnose a Legionella infection.

Legionnaires' disease has similar symptoms to some types of pneumonia, but it can also cause diarrhea and confusion. Legionella bacteria can also cause Pontiac fever, a milder, flu-like illness that doesn't infect your lungs. 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 types of systems 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. You usually can't get the infection through drinking the water, unless you aspirate it (accidentally breathe the water into your lungs) The bacteria do not spread from person to person. But there can be a disease outbreak if 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 if you:

• Are over the age of 50
• Are a current or former smoker
• Have a chronic disease such as diabetes or kidney failure
• Have a chronic lung disease such as COPD or emphysema
• Have a weakened immune system due to a disease such as HIV or cancer, or are taking medicines that suppress the immune system
• Live in a long-term care facility
• Have recently stayed in a hospital or had surgery requiring anesthesia

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

Other names: Legionnaires' disease testing, Legionellosis testing, Legionella pneumophila

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. It's important to get the right diagnosis and treatment to 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 14 days after exposure to Legionella bacteria and may include:

• Cough
• High fever
• Chills
• Headache
• Chest pain
• Shortness of breath
• Fatigue
• Nausea and vomiting
• Diarrhea
• Confusion

What happens during a Legionella test?

Legionella tests are usually done using urine or sputum. A blood test may be done to see if you have been exposed to the bacteria.

During a clean catch urine test:

You will need to give a urine sample for the test. A health care professional may give you a cleansing wipe, a small container, and instructions for how to use the "clean catch" method to collect your urine sample. It's important to follow these instructions so that germs from your skin don't get into the sample:

1. Wash your hands with soap and water and dry them.
2. Open the container without touching the inside.
3. Clean your genital area with the cleansing wipe:
   • For a penis, wipe the entire head (end) of the penis. If you have a foreskin, pull it back first.
   • For a vagina, separate the labia (the folds of skin around the vagina) and wipe the inner sides from front to back.
4. Urinate into the toilet for a few seconds and then stop the flow. Start urinating again, this time into the container. Don't let the container touch your body.
5. Collect at least an ounce or two of urine into the container. The container should have markings to show how much urine is needed.
6. Finish urinating into the toilet.
7. Put the cap on the container and return it as instructed.

If you have hemorrhoids that bleed or are having your menstrual period, tell your provider before your test.

During a sputum test:

Sputum is a thick type of mucus made in your lungs. If you have an infection or chronic illness affecting the lungs or airways, sputum can settle in your lungs, and you can also cough it up. During the sputum test:

• You may be asked to rinse your mouth with water before the sample is taken.
• Your 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 to 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 provider. Your provider may consider your symptoms, medical history, and the results of other tests to understand the results of your Legionella test.

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 other 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

If you have Legionnaires' disease, you may have symptoms such as fatigue and muscle aches for several months after treatment. If there's an outbreak of Legionnaires' disease in a building where you work or live, ask your provider if you need to do anything to reduce your risk of infection.

Legionnaires' disease got its name in 1976 after a group of people attending an American Legion convention became ill with pneumonia.