Influenza, commonly known as flu, is an infectious disease of bird and mammal caused by RNA virus of the family Orthomyxoviridae (the influenza viruses). The name influenza comes from the , meaning "influence", . In humans, common symptoms of the disease are the chills, then fever, sore throat, muscle pains, severe headache, cough, weakness and general discomfort. In more serious cases, influenza causes pneumonia, which can be fatal, particularly in young children and the elderly. Although it is sometimes confused with the common cold, influenza is a much more severe disease and is caused by a different type of virus. Influenza can produce nausea and vomiting, especially in children, but these symptoms are more characteristic of the unrelated gastroenteritis, which is sometimes called "stomach flu" or "24-hour flu".
Typically influenza is transmitted from infected mammals through the air by coughs or sneezes, creating aerosols containing the virus, and from infected birds through...
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