<human>:  Why is the Bird flu called Bird flu?
<bot>: The name Bird flu comes from the fact that the virus was first identified in birds. The virus is called H5N1 because it belongs to the family of viruses called Influenza A. Influenza A viruses infect a wide range of animals, including humans. The bird flu is different from other strains of the influenza A virus because it is a strain that can be transmitted from birds to humans.