If bird flu was the issue then every wild bird would be dropping dead. If wild birds can survive bird flu then theirs no reason why chickens and turkeys can’t survive. Killing off 100 million chickens just because one had bird flu is seriously messed up. The factors of birds inside hatchery, vs birds outside and free to roam play a factor because the free roaming birds are less susceptible to bird flu but the consequences is that dust brings the bird flu into enclosed chicken buildings, or workers bring it in on their clothes or shoes. Surprisingly swine flue has not hit the headlines, but you just wait.