It's harder to quarantine when other animals that can get infected can fly. It can spread via dust too. Animal farms of this size are effectively in a permanen

It's harder to quarantine when other animals that can get infected can fly. It can spread via dust too. Animal farms of this size are effectively in a permanent state of quarantine anyway. Employees take chemical showers and change clothes to ingress and egress. Anyway, it's probably cheaper to start from scratch. Quarantine would mean spending millions to keep chickens alive you couldn't sell or do anything with and hope the flu eventually spreads through the flock and no samples come back positive AND it doesn't spread the entire time.