General Background on Avian Influenza
(Avian Flu, Bird Flu)
Avian influenza, or bird flu or avian flu, is a common, naturally occurring virus in birds that has many forms or subtypes. Scientists believe all birds are susceptible to infection by some form of avian flu. Some birds, like waterfowl, can be infected with the virus but develop no signs of illness. In addition, the potency (virulence) varies greatly among the various subtypes of the avian flu virus.
Virulence is classified as either low pathogenic avian influenza (LPAI) or high pathogenic avian influenza (HPAI). Most avian flu subtypes are LPAI and cause little or no signs of illness in domestic or wild birds and pose no threat to human health. These subtypes are found every year in waterfowl and other birds. HPAI viruses are associated with the H5 and H7 subtypes. Some strains of the H5 and H7 subtypes are extremely infectious and fatal to domestic poultry, sometimes posing a threat to human health.
The high pathogenic H5N1 strain of avian flu (also known as Asian strain H5N1) has been found in Asia, Europe and Africa. The virus has affected millions of domestic poultry and is receiving great attention within the medical community because it has resulted in a 60 percent death rate in the more than 320 cases in humans since 1997. There is no evidence for sustained human-to-human spread of this flu, but a limited number of possible human-to-human transmissions have been reported.
The high pathogenic H5N1 strain of avian flu has not been found in North America (as of 8/29/2007).
Role of Migratory Birds in Transmission of Avian Flu
Migratory birds, like waterfowl, are known to carry different subtypes of avian flu. However, the role of migratory birds in the spread of high pathogenic H5N1 avian flu is unknown and is under active investigation in Europe and Asia. Some waterfowl and shorebird species migrate between Alaska and Asia providing a possible transmission route into North America. This is of special concern to the poultry industry, because this strain of avian flu is highly virulent to domestic fowl. The impact on that industry could be enormous.
There is no evidence to suggest that migratory birds have transmitted the high pathogenic H5N1 strain of avian flu to humans. Indeed, it is highly unusual for an avian flu to be transmitted directly between different kinds of animals. This strain has been found in pigs, cats and a few other species, so this heightens the concern that it may also be transmittable to humans.
Monitoring Avian Flu in North America
Migratory Birds: The high pathogenic H5N1 strain of avian flu is presently not in North America, and the probability of when and if it may arrive cannot be predicted. In the United States, health and management of migratory birds are within the jurisdiction of the U.S. Fish & Wildlife Service. The USFWS is actively participating in the monitoring and reporting of avian flu among migratory birds, in consultation with other federal and state wildlife agencies.
Poultry Operations: The U.S. Department of Agriculture (USDA) works together with federal, state and industry partners to protect the U.S. against the rapid spread of highly pathogenic H5N1 avian influenza. Safeguards include trade restrictions, wild bird monitoring, federal-state-industry testing of poultry, federal inspection programs at slaughter and processing plants and rapid response plans.
Public Health: The federal government has established a Web site for avian flu. The site identifies the lead agencies responsible for monitoring of, and response to, emerging information on avian flu. DU will continue to monitor emerging avian flu information from these and other sources.
While the high pathogenic H5N1 strain of avian flu is presently not a threat to the U.S. public, DU encourages people to follow the standard precautions offered by the National Wildlife Health Center for protecting themselves against diseases w hen handling harvested animals to minimize risks.
For Further Reference:
Bird Flu FAQ's
Bird Flu Meeting Brings World’s Top Influenza and Waterfowl Authorities to the Table
World Health Organization and DU Meet to Discuss Bird (Avian) Flu