Influenza

n. contagious disease caused by a virus and characterized by fever and inflammation of the respiratory tract

Influenza, commonly known as flu, is an infectious disease of birds and mammals caused by  RNA viruses of the family Orthomyxoviridae (the influenza viruses). In humans, common symptoms of influenza infection are fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort. In more serious cases, influenza causes pneumonia, which can be fatal, particularly in young children and the elderly. Sometimes confused with the common cold, influenza is a much more severe disease and is caused by a different type of virus. Although nausea and vomiting can be produced, especially in children, these symptoms are more characteristic of the unrelated gastroenteritis, which is sometimes called "stomach flu" or "24-hour flu."
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Usually referred to as the flu or grippe, influenza is a highly infectious respiratory disease. [more]Influenza - Community and Resources

Noun
1. an acute febrile highly contagious viral disease
(synonym) flu, grippe
(hypernym) contagious disease, contagion
(hyponym) Asian influenza, Asiatic flu

n. influenza, contagious disease caused by a virus and characterized by fever and inflammation of the respiratory tract