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Flu SyndromeCommonly known as the flu, Influenza is an infectious disease of birds and mammals caused by an RNA virus of the family Orthomyxoviridae (the influenza viruses). In more serious cases, influenza causes pneumonia, which can be fatal, particularly in young children and the elderly. Although the common cold is sometimes confused with influenza, it is a much less severe disease and caused by a different virus.
Typically, influenza is transmitted from infected mammals through the air by coughs or sneezes creating aerosols containing the virus, and from infected birds through their droppings. Influenza can also be transmitted by saliva, nasal secretions, feces and blood.
Vaccinations against influenza are most common in high-risk humans in industrialised countries and farmed poultry. A vaccine formulated for one year may be ineffective in the following year, since the influenza virus changes every year and different strains become dominant.
Common symptoms of flu (influenza) are