Where do the North American strains of avian influenza come from?
In North America there are two major reservoirs or sources of avian influenza: 1) Wild ducks and geese in Canada and the U.S. naturally carry a wide range of avian influenza viruses. None of these North American strains have been implicated directly in killing large numbers of poultry and none are known to have made people sick. Of the many variations of the virus found in wild waterfowl, a few have the potential to mutate after they infect a poultry flock into forms that will kill large numbers of birds. In strains native to North America, the virus must cycle through thousands of domestic poultry before it has the opportunity to change into a highly pathogenic strain capable of killing large numbers of chickens or turkeys. No cases are known where an avian influenza virus has mutated into the deadly form in a small flock of chickens or turkeys. If the virus does change into a deadly form, it can then spread to backyard flocks and kill large numbers of birds. 2) The 100 or more live b
