Swine flu, bird flu, mad cow disease, animals have a pretty poor record when it comes to disease, so why are they completely unaffected by the reanimation process? Animals die, animals get bitten, but no animals come back from the dead. They are immune to the 'virus', though that fact could be evidence to suggest its not even a virus at all. Or it could point to an engineered disease that is designed specifically for humans, while not spoiling the livestock and animals used for sustainability.