LEGIONNAIRES' DISEASE

LEGIONNAIRES' DISEASE, an acute infection manifested principally by pneumonia, takes its name from its first known victims—military veterans who attended the Pennsylvania state convention of the American Legion in Philadelphia, 21–24 July 1976. Within days after the convention, reports reached the legion's headquarters that a number of attendees who stayed at the Bellevue-Stratford Hotel had died of pneumonia. Before the epidemic subsided, 221 cases had been found—182 Legionnaires and 39 others who had been near the hotel—and 34 had died. The cause at first was unknown, although speculation centered on a chemical toxin or sabotage. In December 1976 Joseph McDade at the Centers for Disease Control in Atlanta, Georgia, demonstrated that a previously unknown bacterium, Legionella pneumophila, was the causative agent.

Although Legionella will not grow in the usual diagnostic media of the laboratory, it is hardy and common in nature. It grows in fresh water, preferring a temperature close to that of the human body and an atmosphere laden with carbon dioxide. It is found in potable water systems on the hot water side and in recirculating towers of heat-exchange systems. At the Bellevue-Stratford it was probably spread through the air-conditioning system. There are many strains of Legionella, which cause diseases of varying severity, including 1 to 2 percent of all pneumonia cases in the United States. At the other end of the Legionella spectrum is Pontiac fever, a nonfatal disease in which pneumonia does not occur.

BIBLIOGRAPHY

Fraser, David W. "Legionnaires' Disease." In The Cambridge World History of Human Disease. Edited by Kenneth F. Kiple. Cambridge; New York: Cambridge University Press, 1993.

Lattimer, Gary L., and Richard A. Ormsbee. Legionnaires' Disease. New York: Marcel Dekker, 1981.

Elizabeth W.Etheridge/c. w.

See alsoCenters for Disease Control and Prevention ; Epidemics and Public Health .