Legionnaires' Disease

Legionnaires’ disease is a serious type of pneumonia you get when Legionella bacteria infect your lungs. Symptoms include high fever, cough, diarrhea and confusion. You can get Legionnaires’ disease from water or cooling systems in large buildings, like hospitals or hotels. Legionnaires’ disease can be life-threatening.


Symptoms of Legionnaires’ disease include high fever, cough, diarrhea, muscle aches, headache, nausea, confusion and more.
Legionnaires’ disease can cause pneumonia-like, gastrointestinal (gut) or neurological (brain) symptoms, starting two to 14 days after exposure to Legionella.

What is Legionnaires' disease?

Legionnaires’ (LEE-juh-nares) disease is a type of pneumonia (lung infection) you get from breathing in Legionella bacteria. It can affect your lungs, brain and gut (gastrointestinal tract). Legionella also causes Pontiac fever, a less serious illness with flu-like symptoms. Legionnaires’ disease can be life-threatening.


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What’s the difference between Legionnaires’ disease and pneumonia?

You get Legionnaires’ disease when Legionella infects your lungs. Most people with Legionnaires’ disease who are hospitalized have fever and cough but may also have other pulmonary symptoms such as diarrhea and confusion.

Who’s more likely to get Legionnaires’ disease?

Most people don’t get Legionnaires’ disease, even if they’ve been around Legionella bacteria. But some people are more likely to get sick with a Legionella infection than others. You have an increased risk of getting Legionnaires’ disease if you:

  • Are older than 50.
  • Smoke or used to smoke cigarettes.
  • Have a weakened immune system. Certain medical conditions (like HIV, diabetes, cancer and kidney or liver disease) and medications can compromise your immune system.
  • Have a long-term respiratory illness, such as chronic obstructive pulmonary disease (COPD) or emphysema.
  • Live in a long-term care facility.
  • Have stayed in a hospital recently.
  • Have had surgery requiring anesthesia recently.
  • Have received an organ transplant recently.


How common is Legionnaires’ disease?

Up to 18,000 people are hospitalized with Legionnaires’ disease each year in the U.S. It’s more common between June and October.

Symptoms and Causes

What are the symptoms of Legionnaires’ disease?

Legionnaires’ disease causes pneumonia-like symptoms that start two to 14 days after exposure to Legionella. You may also have neurological (brain) and gastrointestinal (gut) symptoms.

Symptoms of Legionnaires’ disease include:


What causes Legionnaires’ disease?

Legionella bacteria causes Legionnaires’ disease. While there are at least 60 species of Legionella, Legionnaires’ disease is most often caused by Legionella pneumophila. You get Legionnaires’ disease when Legionella infects your lungs.

Legionella is found naturally in lakes, streams and soil, but it can also contaminate drinking water and air systems, especially in large buildings. You can breathe small droplets of water directly into your lungs, or water in your mouth can get into your lungs accidentally — for instance, if it goes “down the wrong pipe” (aspiration).

How do you get Legionnaires’ disease?

You can get Legionnaires’ disease by breathing in mist (aerosolized water) contaminated with bacteria or from getting contaminated water in your lungs (aspirating).

Outbreaks of Legionnaires’ disease have been described in hotels, hospitals, long-term care facilities or cruise ships, but most cases are random.

You can get Legionnaire’s disease from:

  • Hot tubs.
  • Shower heads.
  • Faucets.
  • Humidifiers.
  • Decorative water features.
  • Heating and cooling systems (usually only in large buildings).
  • Intubation during surgery.
  • Dirt (soil).

Is Legionnaires’ disease contagious?

No, Legionnaires’ disease isn’t contagious. You can’t get it from another person.

Diagnosis and Tests

How is Legionnaires’ disease diagnosed?

Urine (pee) and sputum (mucus or phlegm) tests are the most common ways to diagnose Legionnaires’ disease. Your healthcare provider will also get pictures of the inside of your chest with an X-ray or CT scan.

Your healthcare provider will perform a physical exam and ask you about your health and travel history.

What tests will be done to diagnose this condition?

Tests to look for signs of Legionella bacteria and imaging are done to diagnose Legionnaires’ disease. These include:

  • Urine or sputum tests: You’ll pee in a cup (urine test) or cough and spit in a tube (sputum test). Your healthcare provider will test your pee or mucus for signs of Legionella.
  • Blood tests: Your provider will take blood from your arm with a needle. Your healthcare provider will look for signs of Legionella in your blood. They can also use blood tests to understand how well your organs are working.
  • Imagining (chest X-ray or CT scan): Your provider will use a machine to take pictures of your lungs. They can use these images to look for changes in your lungs, like pneumonia.
  • Bronchoscopy: Your provider may use a thin, lighted tube to look at the inside of your lungs. They’ll take samples to be tested for signs of Legionella.
  • Thoracentesis: You may need to have fluid drained from the outside of your lungs (thoracentesis). Your provider will test this fluid for signs of Legionella.

How do you know if you have Legionnaires’ disease?

The only way to know if you have an infection with Legionella is to be diagnosed by a healthcare professional. Legionnaires’ disease has symptoms of pneumonia, plus diarrhea and mental changes, like confusion.

Management and Treatment

How is Legionnaires’ disease treated?

Legionnaires’ disease is treated with antibiotics. You may get antibiotics through your veins (IV) or in a pill that you swallow. If you’re having trouble breathing, your provider may give you treatments to help you get enough oxygen. You’ll probably have to stay in the hospital while you’re treated.

What medications are used to treat Legionnaires’ disease?

Antibiotics used to treat Legionnaires’ disease include:

You may also receive extra oxygen through a tube in your nose or a mask. In serious cases, you may need to have a machine breathe for you until you can do it on your own again (mechanical ventilation).


How can I reduce my risk of Legionnaires’ disease?

Building managers can reduce the risk of Legionnaires’ disease by maintaining and properly disinfecting water and ventilation systems.

You can reduce your risk at home by making sure shower heads, faucets, hot tubs and humidifiers are properly cleaned. Don’t use plain water in place of windshield wiper fluid in your car.

Outlook / Prognosis

What can I expect if I have Legionnaires’ disease?

Legionnaires’ disease can make you very sick, and you’ll probably need to be treated in the hospital. Fortunately, it can be treated with antibiotics.

After you go home from the hospital, you may still need to take medications to make sure the infection goes away completely.

For several months afterwards, you may still have:

  • Fatigue.
  • Problems with balance or coordination.
  • Trouble walking.
  • Slurred speech.
  • Muscle aches.

Talk to your healthcare provider if you have concerns about ongoing symptoms.

Complications of Legionnaires’ disease

Legionnaires’ disease can have life-threatening complications that affect your organs or muscles. They include:

  • Respiratory failure: When your lungs can’t get enough oxygen to your blood, you’re in respiratory failure. You’ll need a machine to breathe for you (mechanical ventilation).
  • Acute kidney injury (AKI or acute renal failure): When your kidneys stop working, they can’t filter waste out of your blood. AKI is treated with medications or a machine to filter your blood for you (dialysis).
  • Encephalopathy: Neurologic symptoms, like confusion, balance problems and trouble talking, may get worse.
  • Empyema: Empyema is when you have pockets of pus in the space around your lungs. You may need a chest tube to treat empyema.
  • Inflammation of your heart: Bacterial infections in your heart can cause inflammation. This can sometimes be treated with medications.
  • Rhabdomyolysis: Rhabdomyolysis is a condition where muscle damage causes your muscles to break down. Rhabdomyolysis is treated by flushing toxins out of your body.

Can you survive Legionnaires’ disease?

Legionnaires’ disease is very serious, but most people survive. If treated, lung infections with Legionella are fatal about 5% to 10% of the time. If not treated, Legionnaires’ disease is fatal 30% to 80% of the time.

Living With

When should I see my healthcare provider?

If you have symptoms of Legionnaires’ disease, contact your healthcare provider right away. If there’s an outbreak of Legionnaires’ disease in a building where you’ve worked or stayed, ask your provider what precautions you should take.

When should I go to ER?

If you have a high fever, are struggling to breathe, are coughing up blood or have any neurological symptoms (like balance or speech problems or confusion), go to your nearest ER.

What questions should I ask my doctor?

  • How long will it take for me to feel better?
  • How do I take my medication?
  • What new or ongoing symptoms should I be concerned about?

A note from Cleveland Clinic

Legionnaires’ disease is treatable but can be life-threatening. If you think you have Legionnaires’ disease or have stayed in an area with an outbreak, contact your healthcare provider right away.

Medically Reviewed

Last reviewed on 07/27/2022.

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