From A Dictionary of the History of Medicine (1999):
Influenza [Italian: influenza] Thomas Willis (1621-1673) and Thomas Sydenham (1624-1689) described it. The term was first used to denote a characteristic illness found in northern Italy. It was previously known as epidemic catarrhal fever and many outbreaks occured in England between 1729 and 1847. The name was first used in England by John Huxam (1692-1768). One of the worst epidemics occured in 1918-1919, killing about 30 million people worldwide. The influenza of swine was first shown to be due to a virus by an American virologist, Richard Edwin Shope (1901-1966), and the first cultured by Australian immunologist, Sir Frank Macfarlane Burnet (1899-1985) in 1935. The influenza B virus was isolated independently by Thomas Francis (1900-1969) and Thomas Pleines Magill (b 1903), in 1940.