1976 Philadelphia Legionnaires' disease outbreak 1976 Philadelphia Legionnaires' disease outbreak The 1976 Legionnaires disease outbreak, occurring in the late summer in Philadelphia, Pennsylvania, was the first occasion in which a cluster of a particular type of pneumonia cases were determined to be caused by the "Legionella pneumophila" bacteria. Previous outbreaks were retroactively diagnosed as being most probably caused by Legionella bacteria. On July 21, 1976, the American Legion opened its annual three-day convention at the Bellevue-Stratford Hotel in Philadelphia, Pennsylvania. More than 2,000 Legionnaires, mostly men, attended the convention. The date and city were chosen to coincide with America’s celebration of the 200th anniversary of
1976 Philadelphia Legionnaires' disease outbreak which then spread it through the building. This finding prompted new regulations worldwide for climate control systems. Complicating the situation was a fear among the public that the original cluster of 14 cases, six of whom died within a few days of each other, represented an outbreak of swine flu. The total number of cases reached 211, and of those, 29 had died. At the time of the outbreak, epidemiological investigation protocols did not include active participation by both the laboratory specialists and investigators. No effective communication existed between scientists in the field interviewing patients, and those in the laboratory