Infected birds shed influenza virus in their saliva, nasal secretions, and feces. Susceptible birds become infected when they have contact with contaminated excretions or with surfaces that are contaminated with excretions or secretions.

Naturally occurring avian influenza viruses in wild birds are generally associated with waterfowl (ducks and geese), gulls, and some species of shore birds and typically do not cause illness in these birds. The viruses can occasionally be transmitted from these wild birds to domestic birds such as chickens, quail and turkeys. In some cases these viruses can cause severe disease in domestic birds.

Infected birds shed flu virus in their saliva, nasal secretions, and feces (droppings). Susceptible birds become infected when they have contact with contaminated excretions or surfaces that are contaminated with excretions.

There are many unanswered questions regarding the role of migratory birds in spreading highly pathogenic avian flu. Wild waterfowl have probably carried influenza A viruses, with no apparent harm, for centuries. They are known to carry viruses of the H5 and H7 subtypes, but usually of the low pathogenic form. Considerable evidence suggest that migratory birds can introduce to poultry low pathogenic H5 and H7 viruses, which then mutate to the highly pathogenic form.

Wild birds may have influenza viruses in their digestive tracts. The virus is shed in their wastes into water where the birds congregate and thereby spreads to other wild birds. It also can spread via waste matter from wild birds to domestic birds, such as chickens and ducks, through contaminated water or food. In domestic birds (poultry), certain types of avian influenza can be deadly.

While currently there are unconfirmed reports of people being infected with H5N1 from dead wild birds, exposure to domestic and wild birds potentially infected with H5N1 should be avoided. The only documented cases of transmission to humans are from poultry; these cases include both highly pathogenic and low pathogenic strains of avian influenza. the present time, close contact with infected domestic poultry has been the primary way that people have become infected with the HPAI H5N1 virus.

Most avian influenza viruses have been isolated from wild waterfowl (ducks, geese, and swans) and shorebirds (wading birds), gulls, and terns. With rare exceptions, 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.

If the avian influenza virus (H5N1) is present in a wild bird, it may be possible for a human to get the disease. However, there have been no known cases of humans getting avian influenza from wild birds. As of January 2006, avian influenza has not been identified in any wild or domestic bird in the United States. The following websites provide guidelines for hunters and others who may come in contact with wild birds:

To date, there have been no known cases of H5N1 anywhere in North America. At the AZA-accredited institutions with birds, animal care experts already have a regular routine to carefully monitor the health of their birds, as well as the other animals. Experts at AZA zoos and aquariums know these animals better than anyone else, and are attuned to the slightest behavior change that may indicate that an animal is ill.

In rare instances, people can contract avian influenza. The exact mode of transmission from birds to people is not known, but it is obvious that it has mutated and developed the ability to pass from birds to human but most human cases of avian flu have been traced to direct contact with live infected birds or their dropping

Avian influenza, or "bird flu" or "avian flu" is an infection caused by avian (bird) influenza (flu) viruses. These flu viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, bird flu is very contagious among birds and can make some domesticated birds, including chickens and ducks, very sick and kill them.

USGS and FWS, in collaboration with State of Alaska biologists have been strategically sampling migratory birds for H5N1 in the Pacific Flyway for several months. These efforts complement a series of ongoing avian influenza studies being conducted by the USDA and its university partners in Alaska, where birds that regularly migrate between Asia and North America are known to congregate and to nest. The U.S. Geological Survey, U.S. Fish and Wildlife Service, and U.S.