Influenza a subtype h5n1 (avian flu) has been documented in poultry in both east and southeast asian countries. this form of avian flu is highly contagious from bird to bird but rarely is passed from human to human. there is a large amount of concern that the h5n1 strain might mutate, making it easier to be passed from human to human, carrying with it a high mortality rate. what is the main concern if the h5n1 strain does mutate?