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| | Avian Flu - MSN Encarta |
 | | Avian Flu, also known as bird flu, an infectious disease of wild and domestic birds, caused by a range of viruses known as Type A influenza viruses. |
 | | Avian influenza was not known to directly infect humans until 1997, when an outbreak in Hong Kong, China, caused by infected poultry, sickened 18 people, killing 6 of them. |
 | | Although humans have a degree of immunity to the influenza subtypes that circulate during the winter flu season, the human immune system is unaccustomed to recognizing and fighting off avian influenza. |
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