Definition of influenza in US English:



  • A highly contagious viral infection of the respiratory passages causing fever, severe aching, and catarrh, and often occurring in epidemics.

    Also called flu
    • ‘Among the respiratory viruses, influenza viruses are known to cause outbreaks globally.’
    • ‘Other viral illnesses include influenza, the common cold, Lassa fever, and ebola.’
    • ‘You should treat this season of influenza exactly the way you treat any other influenza.’
    • ‘Smoking cessation also reduces the risk of death after a stroke and of death from pneumonia and influenza.’
    • ‘Frequently referred to as the flu, influenza is a respiratory illness which is caused by a virus.’
    • ‘The best way to avoid influenza or reduce its symptoms is to get a flu shot every year.’
    • ‘We investigated uptake of pneumococcus and influenza vaccine in all children with diabetes in our area.’
    • ‘It is not less infectious than measles or influenza, and even if it were, it is much more fatal.’
    • ‘On a search for me around France, he had caught a deadly fever as well as influenza.’
    • ‘Others are accounted for by a variety of viruses such as influenza.’
    • ‘Many biological warfare agents cause illness that could be mistaken for common diseases such as influenza.’
    • ‘Most topical is the risk of pandemic influenza, which seems to be the highest in three decades.’
    • ‘An infected person can spread influenza from up to a day before becoming ill and up to eight days after.’
    • ‘Symptoms and signs of influenza in children are not specific and can mimic a range of other common respiratory viral pathogens.’
    • ‘It also caused post-flood diseases for children like influenza, diarrhea and fever.’
    • ‘So far no H5N1 influenza virus infection in birds or humans has been reported in India.’
    • ‘Residents with influenza should be in a separate room or with other flu sufferers.’
    • ‘Vaccinating children with asthma against influenza has never really caught on.’
    • ‘Elderly people are at particular risk of serious illness if they contract influenza.’
    • ‘Epidemics of influenza are associated with increases in mortality and morbidity.’


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 which began in Italy in 1743, later adopted in English as the name of the disease.