The H5N1 avian influenza virus is mutating to evade immune defenses in mammals following prior infection or vaccination.

The detection of bird flu in a sheep is another sign that the H5N1 virus is adapting to hop to new hosts ...

"Similarly, the stalk region of the bird flu virus closely resembles the same structure of seasonal influenza, which makes it possible for stalk-targeting antibodies to provide universal protection." ...

The death toll from the flu of 1918 was more than a half ... of our burgeoning understanding of the structure and function of the virus itself. The virus is, after all, the ‘mass murderer ...