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, sputum, or in some cases in lung tissue.

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.

Why this test is done

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

How to prepare

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

Because a sputum culture is often scheduled in the morning, your provider may encourage you to drink more water the night prior. This is because drinking more water can increase the amount of sputum. You may also be asked not to eat for one or two hours before the test.

If you get a BAL and/or bronchoscopy, you may be asked to fast (not eat or drink) for up to twelve hours before the test.

You may also need to stop taking certain medicines before a sputum culture and a BAL/bronchoscopy. So, tell your provider about everything you take. Antibiotics may affect bacterial growth and your results, especially those of a sputum culture.

But don't stop taking any medicines unless your provider tells you to.

Sample type

Blood Urine Sputum

Other names for this test

Legionnaires' disease testing, Legionellosis testing, Legionella pneumophila