Legionnaires' disease is a severe bacterial infection of the respiratory tract, caused by Legionella pneumophila.

The disease acquired its name as a result of an outbreak of illness during the 1976 convention of the American Legion held in Philadelphia. At least 180 American Legion members attending the conference contracted a mysterious pneumonia that did not respond to conventional antibiotic treatment. Twenty nine people died. Eventually, the villain turned out to be Legionella pneumophila, a...