Bird flu refers to an illness caused to a particular host caused be any of species of influenza virus. This bird flu is also called as Avian Influenza in which birds are affected by a particular influenza A virus. It is usually spread from bird to bird. Bird flu is technically caused by H5N1 and H7N9 bird flu viruses. This influenza virus attacks the birds and when humans consume them, they will be affected by this virus, where humans do not have any immunity against the virus and so causes severe effects.
Prevention: There is no treatment for bird flu and the virus is most effective to humans and so prevention can only be done by taking certain precautionary measures like will preferring birds as a source of food better to check them whether they are affected by any virus or not.
The global mortality rate from the 1918/1919 pandemic is not known, but an estimated 10% to 20% of those who were infected died. With about a third of the world population infected, this case-fatality ratio means 3% to 6% of the entire global population died. Influenza may have killed as many as 25 million people in its first 25 weeks. Older estimates say it killed 40–50 million people, while current estimates say 50–100 million people worldwide were killed.