Influenza, commonly known as the flu, is an infectious disease that infects birds and mammals (primarily of the upper airways and lungs in mammals) and is caused by an RNA virus of the Orthomyxoviridae family (the influenza viruses). The most common and characteristic symptoms of influenza in humans are fever, sore throat, myalgia (muscle pains), severe headache, cough, and malaise (weakness and fatigue).
A cold and a 'stomach flu' are very different from a flu. Influenza can be far more severe than the common cold and can even lead to death. Influenza and the common cold are caused by very different viruses. Gastroenteritis is commonly called "stomach flu" or "24 hour flu"; but that is a misnomer as it is not connected with actual flu.
Flu rapidly spreads around the world in seasonal epidemics, killing millions of people in pandemic years and hundreds of thousands in nonpandemic years. It creates health care costs and lost productivity. Three influenza pandemics in the 20th century, each following a major genetic change in the virus, killed millions of people all over the world. The world's current major influenza pandemic threat is H5N1; but it is at present mostly a flu in birds, not in people.
The term influenza has its origins in 15th century Italy, where the cause of the disease was ascribed to unfavourable astrological influences. Evolution in medical thought led to its modification to "influenza di freddo", meaning "influence of the cold", which by the 18th century became the prevalent terminology in the English-speaking world as well.
Please chick the wellcoming chicken to hear the bird stars singing heartly for the NEW YEAR, the terrible infection of avian influenza and their possibly unlucky fate. (Attention: Hi-pop music in Chinese !!!)