- a highly contagious viral infection of the respiratory passages causing fever, severe aching, and catarrh, and often occurring in epidemics. Also called flu.
mid 18th century: from Italian, literally 'influence', from medieval Latin influentia (see influence). The Italian word also has the sense 'an outbreak of an epidemic', hence 'epidemic'. It was applied specifically to an influenza epidemic that began in Italy in 1743, later adopted in English as the name of the disease