U.S. authorities are considering imposing tougher restrictions in Arkansas to contain a virulent strain of avian flu in the heart of America's poultry region in a bid to minimize international trade disruptions and contain the virus. The H5N2 flu discovered in Arkansas last week is the state's first case of a strain that causes massive internal hemorrhaging in poultry, can kill nearly every bird in an infected flock within 48 hours, and is prone to mutate.