Interesting thing I discovered when researching H5N1 and poultry culling. It turns out that some countries (notably, China) vaccinate their birds, and most coun

Interesting thing I discovered when researching H5N1 and poultry culling. It turns out that some countries (notably, China) vaccinate their birds, and most countries (notably USA) do not allow the import of vaccinated poultry. This is, apparently, because vaccination can hide the virus, and cause it to mutate into more resistant, infectious forms. Another interesting fact: all countries cull their birds in case of an outbreak, even those that vaccinate, this is not a uniquely US thing.