USGS Frequently Asked Questions

Answer:

• Most avian influenza viruses have been isolated from wild waterfowl (ducks, geese, and swans) and shorebirds (wading birds), gulls, and terns.
• With rare exception, the thousands of flu 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 other times of the year, infection rates are usually less than 1 percent.
• In shorebirds, infection rates are highest during the spring migration, although in comparison with waterfowl, their infection rates are much lower.