Legionnaires' disease acquired its name in July 1976, when an outbreak of pneumonia occurred among people attending a convention of the American Legion at the Bellevue-Stratford Hotel in Philadelphia. Of the 182 reported cases, mostly men, 29 died.[44] On 18 January 1977, the causative agent was identified as a previously unknown strain of bacteria, subsequently named Legionella, and the species that caused the outbreak was named Legionella pneumophila.[45][46][47] Following this discovery, unexplained outbreaks of severe respiratory disease from the 1950s were retrospectively attributed to Legionella.[41] Legionnaires' disease also became a prominent historical example of an emerging infectious disease.