In 1977, the U.S. Centers for Disease Control and Prevention (CDC) isolated Legionella pneumophila, which caused a deadly outbreak of Legionnaires’ disease in a Philadelphia hotel the previous year.

In the summer of 1976, an estimated 4,400 American Legionnaires and guests gathered at a Philadelphia hotel for the 58^th Annual Convention of the American Legion in Pennsylvania. Shortly after the convention, the Centers for Disease Control (CDC) in Atlanta received a call describing a cluster of patients with severe febrile respiratory illness who had attended the convention, some of whom died.

In the months to follow, numerous health officials were deployed to investigate this epidemic. Two hundred twenty-one individuals ultimately met the clinical criteria for the respiratory syndrome known as Legionnaires’ disease (LD); 34 people succumbed to their infections.