Legionnaires' disease on symptom onset dates from past outbreaks. In this way, the eventual likely size of an outbreak can be predicted, enabling efficient and effective use of public health resources in managing an outbreak. The first recognized cases of Legionnaires' disease occurred in 1976 in Philadelphia; among more than 2000 attendees of an American Legion convention held at the Bellevue-Stratford Hotel, 182 attendees contracted the disease and 29 of them died. In April 1985, 175 people in Stafford, England, were admitted to the District or Kingsmead Stafford Hospitals with chest infection or pneumonia. A total of 28 people died. Medical diagnosis
1976 Philadelphia Legionnaires' disease outbreak 25 had died. Both the first week and later, there were 149 Legionnaires who became sick and 33 other persons associated with the hotel or in the area who also became sick. Of these total of 182 cases, 29 persons died. The U.S. Centers for Disease Control and Prevention mounted an unprecedented investigation and, by September, the focus had shifted from outside causes, such as a disease carrier, to the hotel environment itself. In January 1977, the "Legionella" bacterium was finally identified and isolated and was found to be breeding in the cooling tower of the hotel’s air conditioning system,