Which species of wild birds are the primary carriers of avian influenza?
Most avian influenza viruses have been isolated from wild waterfowl, shorebirds, and wading birds. With rare exceptions, the thousands of AI isolates found in wild birds have been low pathogenic avian influenza and have rarely caused signs of illness. The occurrence of avian influenza in wild ducks in North America reaches its height in late summer and early fall. At most times of the year, infection rates are usually less than 1 percent. In studied shorebirds, infection rates are highest during the spring migration, although in comparison with waterfowl, their infection rates are much lower.
