In 1978, the U.S. Centers for Disease Control and Prevention (CDC) held its first international conference on Legionnaires’ disease. Legionellosis, which includes Legionnairesﾒ disease and Pontiac fever, is a respiratory disease caused by a type of bacteria called Legionella.

Legionella was discovered after an outbreak in 1976 among people who went to a Philadelphia convention of the American Legion. Those who were affected suffered from a type of pneumonia (lung infection) that eventually became known as Legionnaires’ disease.