On Nov. 13, 1978, the U.S. Centers for Disease Control and Prevention (CDC) held its first international conference on Legionnaires’ disease. Legionellosis, which includes Legionnaires’ 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.

Months after the end of the investigation, a CDC microbiologist named Dr. Joseph McDade revisited the lab cultures and was able to isolate a new bacterium. He named it Legionella pneumophila, after the Legionnaires’ convention.