Commonly called the flu; an acute and infectious disease of the respiratory system caused by a virus and characterized by fever, muscle pain, headache, and inflammation of the mucous membranes in the respiratory tract.
An acute contagious viral infection, commonly occurring in epidemics or pandemics, and characterized by inflammation of the respiratory tract and by the sudden onset, fever, chills, muscular pain, headache, and severe prostration. Also called grippe.
A highly contagious infectious disease that is caused by any of various viruses of the family Orthomyxoviridae and is characterized by fever, respiratory symptoms, fatigue, and muscle pain. It commonly occurs in epidemics, one of which killed 20 million people between 1917 and 1919.
Word History Since ancient times, influenza has periodically swept the world. Until recently, people could not tell how this illness, which we call the flu, could spread so widely. Before people knew that organisms cause disease, they thought the stars influenced the spread of influenza. Influenza comes ultimately from the Latin word influentia, meaning “influence of the stars.” Today, however, the stars are no longer blamed for the flu. Inhaling influenza viruses causes the spread of the illness.