Legionnaires’ disease outbreak in Philadelphia in 1976 was mysterious and deadly – 50 years later, scientists know the cause but outbreaks continue

Legionnaires wait to testify before a special congressional inquiry in November 1976 into the cause of the mysterious disease. Bettmann/Bettman Collection via Getty Images

The landmark Bellevue-Stratford Hotel in Philadelphia went out of business after the Legionnaires’ disease outbreak in 1976. Bettmann/Bettman Collection via Getty Images

Soon after Philadelphia hosted America’s bicentennial celebrations in late July 1976, more than 200 attendees of the American Legion Convention at the Bellevue-Stratford Hotel in Philadelphia fell ill with pneumonia symptoms, including fever, cough and trouble breathing.