Robert Lenox, MD, was a medical intern in 1976 when he took care of a man with fever, muscle and body aches and a cough who had attended the American Legion convention in Philadelphia. The man — who rapidly deteriorated and died — became what epidemiologists refer to as “the index case,” the first person with a particular disease to come to the attention of health authorities. His family members approved of an autopsy, and officials at the Centers for Disease Control and Prevention eventually discovered a bacterial infection in the man’s lungs. The disease became known as Legionnaire’s disease, and this particular outbreak sickened 182, killing 29, of those who attended the convention. Lenox explains the signs and symptoms of Legionnaire’s disease and how it is treated today.