What is the definition of Legionnaire Disease?

Legionnaire disease is an infection of the lungs and airways. It is caused by Legionella bacteria.

What are the alternative names for Legionnaire Disease?

Legionella pneumonia; Pontiac fever; Legionellosis; Legionella pneumophila

What are the causes for Legionnaire Disease?

The bacteria that cause Legionnaire disease have been found in water delivery systems. They can survive in the warm, moist air conditioning systems of large buildings, including hospitals.

Most cases are caused by the bacteria Legionella pneumophila. The rest of the cases are caused by other Legionella species.

Spread of the bacteria from person to person has not been proven.

Most infections occur in middle-aged or older people. In rare cases, children can get the infection. When they do, the disease is less severe.

Risk factors include:

  • Alcohol use
  • Cigarette smoking
  • Chronic illnesses, such as kidney failure or diabetes
  • Long-term (chronic) lung disease, such as COPD
  • Long-term use of a breathing machine (ventilator)
  • Medicines that suppress the immune system, including chemotherapy and steroid drugs
  • Older age

What are the symptoms for Legionnaire Disease?

Symptoms tend to get worse during the first 4 to 6 days. They most often improve in another 4 to 5 days.

Symptoms may include:

  • General discomfort, loss of energy, or ill feeling (malaise)
  • Headache
  • Fever, shaking chills
  • Joint pain, muscle aches and stiffness
  • Chest pain, shortness of breath
  • Cough that does not produce much sputum or mucus (dry cough)
  • Coughing up blood (rare)
  • Diarrhea, nausea, vomiting, and abdominal pain

What are the current treatments for Legionnaire Disease?

Antibiotics are used to fight the infection. Treatment is started as soon as Legionnaire disease is suspected, without waiting for results of any lab test.

Other treatments may include receiving:

  • Fluids through a vein (IV)
  • Oxygen, which is given through a mask or breathing machine
  • Medicines that are breathed in to ease breathing

What is the outlook (prognosis) for Legionnaire Disease?

Legionnaire disease can be life threatening. The risk of dying is higher in people who:

  • Have long-term (chronic) diseases
  • Become infected while in the hospital
  • Are older adults

When should I contact a medical professional for Legionnaire Disease?

Contact your provider right away if you have any type of breathing problem and think you have symptoms of Legionnaire disease.



Edelstein PH, Roy CR. Legionnaires' disease and Pontiac fever. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Updated Edition. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 234.

Marrie TJ. Legionella infections. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 314.

  • Condition: Transient Parkinsonism associated with Acute Legionnaires' Disease
  • Journal: BMJ case reports
  • Treatment Used: Ciprofloxacin and Levodopa-Carbidopa
  • Number of Patients: 1
  • Published —
This case report describes a patient with transient parkinsonism associated with acute Legionnaires' disease.
  • Condition: Legionella Pneumonia Complicated by Rhabdomyolysis
  • Journal: BMJ case reports
  • Treatment Used: Azithromycin Monotherapy and Aggressive Fluid Hydration
  • Number of Patients: 1
  • Published —
This case report discusses a 50-year-old man diagnosed with the rare triad of Legionella pneumonia, renal failure and rhabdomyolysis, and who was treated with azithromycin monotherapy and aggressive fluid hydration.
Clinical Trial
  • Status: Recruiting
  • Intervention Type: Other
  • Participants: 46
  • Start Date: August 13, 2019
Nosocomial and Community Acquired Legionella Pneumophila Pneumonia, a Retrospective Case Series
Clinical Trial
  • Status: Recruiting
  • Intervention Type: Other
  • Participants: 120
  • Start Date: September 6, 2017
Legionella Pneumonia's Effect on Olfactory Function