Legionnaires' disease is caused by a type of bacteria called Legionella. People typically get infected by breathing in tiny droplets or mist of water that contain the Legionella bacteria. These droplets can come from man-made water systems such as:
- Hot tubs and whirlpools
- Showers and sink faucets
- Decorative fountains and water features
- Large plumbing systems in buildings like hotels, hospitals, or office buildings
- Cooling towers used in air conditioning systems for large buildings or industrial processes
The bacteria naturally live in freshwater environments like lakes and rivers but usually do not cause illness there. Infection occurs when Legionella grows and spreads in water systems that are not properly maintained, especially in warm water temperatures between 77°F and 113°F. Legionnaires' disease is not spread from person to person. People are more likely to develop the disease if they are older than 50, smokers, or have chronic diseases or weakened immune systems. In summary, the cause of Legionnaires' disease is breathing in mist containing Legionella bacteria that have proliferated in poorly maintained human-made water systems.
