In the summer of 1976, Legionella was thrust into the public spotlight following an outbreak at an American Legion Convention in Philadelphia's Bellevue Stratford Hotel. A total of 221 cases of pneumonia, and 34 deaths, occurred among the more than 4,000 convention attendees as a result of exposure to this previously unidentified bacteria. It wasn't until 1977 that the offending agent, Legionella pneumophila, was finally identified by the Centers for Disease Control (CDC).
However, this was not the first outbreak. Retrospective studies have shown a number of pneumonia outbreaks which we now know were caused by Legionella The earliest documented outbreak of Legionnaires' disease occurred in 1957 in Austin, MN. A total of 78 persons, 46 of whom were employees at a local meat packing plant, were hospitalized with acute respiratory disease of unknown cause. Eventually two of the patients died.1