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.

Last Updated: September 21, 2009

Author: Maria Essig

Medical Review: Kathleen Romito, MD - Family Medicine & Peter Rabinowitz, MD, MPH - Occupational and Environmental Medicine

related physicians

related services

Bon Secours International| Sisters of Bon Secours USA| Bon Secours Health System

This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Privacy Policy. How this information was developed to help you make better health decisions.

© 1995-2010 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.