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Legionella Infection

  1. What is legionella infection?
  2. Risks
  3. Symptoms
  4. Diagnosis
  5. Treatment
  6. Prevention
  7. Other names for legionella infection

What is legionella infection?

Legionella infection, or Legionnaire's disease, is a infection of the airways or lungs with a bacteria called Legionella. It is usually caused by breathing in the bacteria in droplets of contaminated water. Older people and people with a weak immune system are most commonly affected. Legionella infections can cause a pneumonia, and cause symptoms such as fever, weakness, joint pain, shortness of breath, chest pain and a cough. Diagnosis is usually made with a chest X-ray and identification of the Legionella bacteria in phlegm or urine. Antibiotics are needed to treat the infection. If appropriate therapy is started early, most people recover well, but this depends on the health and age of the affected person.


Legionella infection is a lung infection caused by a bacteria called Legionella pneumophilia. This causes a pneumonia in affected people. It is commonly found in artificial water systems like air conditioning systems and usually grow in warm water. Large hotels, hospitals, museums and office blocks have large and complex water supply systems where legionella can spread quickly. The bacteria is spread in small droplets of contaminated water. It doesn't spread directly from person to person. Legionella tends to affect older people much more commonly than younger people. Other people who are at risk of becoming unwell with a Legionella infection are smokers, people with other medical conditions, such as COPD or a weakened immune system, and people who are on a ventilator (a breathing machine).


Symptoms of a Legionella infection include headache, fever, chills, body aches and feeling generally ill. As the pneumonia develops, this causes a cough, shortness of breath and chest pain.


The diagnosis is made based on the symptoms, physical examination and a test which shows the Legionella bacteria. A sample of phlegm (coughed up from the lungs) is the best test, but urine and blood test can also confirm an infection. A chest X-ray is often needed to check for pneumonia.


Legionella infection is treated with antibiotics, usually over a few weeks. Antibiotic therapy might be already indicated with the suspicion of legionella infection even before the confirmed diagnosis. Oxygen with breathing machine and fluids through veins might be needed.


Keeping water systems and reservoirs (cooling units, spas, fountains) clean can help to prevent some cases of Legionnaire's disease. This includes changing the water regularly and using filtered water.

Other names for legionella infection

  • Legionnaire's disease
  • Legionella pneumonia
  • Legionellosis