I wouldn't start buying masks and dipping your chickens in alcohol just yet.
These things happen all the time in the chicken house world.
In Alabama when I was a kid from time to time you'd see a truck load of dead chickens going to the furnace.
They sometimes get "the flu" and it spreads like wildfire in the confined conditions of the chicken house and it's safer to dispose of the whole lot and sanitize the chicken house than risk it spreading to another chicken house. There are DOZENS of bird flu virus that could have caused it that are NOT problematic to people.
It's just that now everyon's so freaked out by the bird flu it gets a lot of press.