What is legionnaires' disease?

A type of pneumonia: It is a type of pneumonia caused by a bacterium called legionella. This bacterium likes to grow in standing water such as in air conditioning units.

Named after the...: Legionnaires convention in 1976 at the bellevue stratford hotel in philadelphia, it is usually a lower respiratory infection (pneumonia) caused by legionella pneumophila usually acquired from aerosols of infected water.

Probably not: Legionnaires' disease is a severe form of pneumonia — lung inflammation usually caused by infection. Legionnaires' disease is caused by a bacterium known as legionella. You can't catch legionnaires' disease from person-to-person contact. Instead, most people get legionnaires' disease from inhaling the bacteria. Older adults, smokers and people with weakened immune systems are particularly suscep.