Pathology. an acute, commonly epidemic disease, occurring in several forms, caused by numerous rapidly mutating viral strains and characterized by respiratory symptoms and general prostration. Compare flu.
2.
Veterinary Pathology. an acute, contagious disease occurring in horses and swine, characterized by fever, depression, and catarrhal inflammations of the eyes, nasal passages, and bronchi, and caused by a virus.
Origin: 1735–45; < Italian < Medieval Latin influentiainfluence
grippe, Also called: flu a highly contagious and often epidemic viral disease characterized by fever, prostration, muscular aches and pains, and inflammation of the respiratory passages
[C18: from Italian, literally: influence, hence, incursion, epidemic (first applied to influenza in 1743)]