Mode of Transmission of Legionella pneumophila

Abstract

Since the discovery ofLegionella pneumophilaas the cause of an outbreak of pneumonic illness at the American Legion Convention in Philadelphia in 1976,^1,2it has become apparent that Legionnaires' disease is a relatively common form of pneumonia in both the community and nosocomial setting.^3,4Despite admirable success in defining the illness and isolating the causative microorganism, investigators from the Centers for Disease Control (CDC), Atlanta, were not able to definitely identify the mode of transmission in the 1976 Philadelphia outbreak. Although the ensuing years have witnessed considerable advances in microbiologic technique as well as the accumulation of a substantial body of data regarding the microbial ecology and epidemiology of the Legionellaceae, the exact mode of transmission has eluded definition. In this article, we will critically examine various theories of transmission of Legionnaires' disease and attempt to place them in perspective in order to define future directions for