Disease, Legionnaire: A disease due to the bacteria Legionella pneumophila found in plumbing, shower heads and water-storage tanks. 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.

Legionnaire disease can cause a massive pneumonia associated with collapse of the respiratory function. It can be an overwhelming and sometimes fatal illness.

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.

The distinguished surgeon/writer Richard Selzer has recounted his own near-fatal experience with Legionnaire disease in "Raising the Dead. A Doctor's Encounter with His Own Mortality" (Whittle/Viking, New York, 1993).