First Time User? Enroll now.
Get Care Now
COVID-19: Vaccine information, visitor restrictions, testing, treatment, and additional resources
Home > Health Library > Legionnaires' disease
Legionnaires' disease is an infection of the lungs (pneumonia) caused by a type of bacteria called Legionella pneumophila.
People develop Legionnaires' disease from breathing in the bacteria, which may be carried in airborne water droplets from contaminated water sources, such as air-conditioning cooling towers, plumbing systems, hot water tanks, and spas. These sources often have warm, stagnant water that allows bacteria to grow. People who work near natural bodies of water do not appear to be at risk.
Legionnaires' disease is not passed from one person to another. It usually occurs in single, isolated cases or in groups of people who are exposed to the same source of infection. Most cases of Legionnaires' disease affect people older than 50 or people whose immune systems are weakened by other diseases or by smoking.
Current as of: February 9, 2022
Author: Healthwise Staff
Medical Review:Kathleen Romito MD - Family Medicine & Adam Husney MD - Family Medicine & Elizabeth T. Russo MD - Internal Medicine
To learn more about Healthwise, visit Healthwise.org.
© 1995-2022 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.