naproxen: a nonsteroidal anti-inflammatory drug (trade name Naprosyn) used in the treatment of arthritis and musculoskeletal inflammation and moderate pain
agent: a substance that exerts some force or effect
legionnaires' disease: acute (sometimes fatal) lobar pneumonia caused by bacteria of a kind first recognized after an outbreak of the disease at an American Legion convention in Philadelphia in 1976; characterized by fever and muscle and chest pain and headache and chills and a dry cough