Birds at zoos across North America are being forced indoors due to the potentially life-threatening risks of avian influenza. Placing birds in the enclosed area allows complete isolation from wild birds that have the flu and risks posed by other zoo animals. Poultry is now being wiped out to avoid a major flu outbreak. Nearly 23 million chickens and turkeys in the U.S. have been euthanized to limit the spread of the virus. It's a virus so contagious that when bird flu cases are found in poultry, officials order the entire flock to be killed.