Disease, Legionnaire: A disease due to the bacteria Legionella pneumophila found in plumbing, shower heads, water-storage tanks and air cooling systems. Outbreaks of Legionella pneumonia have been attributed to evaporative condensers and cooling towers. The bacteria thrives in the mist sprayed from air-conditioning ducts and so it can infest an entire building or airplane. Travelers are especially vulnerable in the closed space within a plane.
The disease was first identified as a sequel of the 1976 convention of the American Legion in some of those who had attended the convention. It was therefore named Legionnaire disease.