Legionnaire's disease was first identified in 1976 when a sudden, severe outbreak of pneumonia took place at a hotel in Philadelphia, Pennsylvania, where delegates to an American Legion convention were staying. The cause of the outbreak was eventually identified as a previously unknown bacterium, given the name Legionnella pneumophilia. This bacterium probably was transmitted through the air. Scientists have determined also that Legionnella can spread through air-conditioning systems. It also thrives in soil and excavation sites.
Usually Legionnaire's disease is contracted in late summer or early fall and its severity ranges from mild to life-threatening. The mortality rate due to Legionnaire's disease is as high as 15 percent. Symptoms include diarrhea, loss of appetite, malaise (bodily discomfort), headache, generalized weakness, recurrent chills and fever accompanied by cough, nausea, and chest pain. Treatment involves administering antibiotics such as Erythromycin™, along with other therapies (among them fluid replacement and oxygen) that treat the symptoms.
Sources: Diseases and Disorders Handbook, pp. 439-41; Larson, David E., ed. Mayo Clinic Family Health Book: The Ultimate Home Medical Reference, p. 921.