Legionnaires’ disease is a serious form of pneumonia caused by the Legionella bacterium, initially identified during a 1976 outbreak at an American Legion convention in Philadelphia. Annually, up to 18,000 individuals in the U.S. are hospitalized due to this disease, primarily during the months of June to October. Approximately 1 in 10 people infected with Legionella may not survive, emphasizing the importance of early detection and treatment for a complete recovery.