The bacteria that cause Legionnaires 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.
Tests and cultures on sputum to identify Legionella bacteria
Urine tests to check for Legionella pneumophila bacteria
Molecular tests with polymerase chain reaction (PCR)
Treatment
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
Outlook (Prognosis)
Legionnaires disease can be life threatening. The risk of dying is higher in people who:
Have long-term (chronic) diseases or compromised immune systems
Become infected while in the hospital
Are older adults
When to Contact a Medical Professional
Contact your provider right away if you have any type of breathing problem and think you have symptoms of Legionnaires disease.
References
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. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 232.
Review Date:
1/22/2023
Reviewed By:
Denis Hadjiliadis, MD, MHS, Paul F. Harron, Jr. Professor of Medicine, Pulmonary, Allergy, and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. Editorial update 01/19/2024.