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Avian influenza is a viral disease caused by various strains of avian influenza viruses that can be classified as low pathogenic avian influenza (LPAI) or highly pathogenic avian influenza (HPAI). It remains a global disease with potential high consequence with the potential to threaten wildlife, agriculture, and human health.
The USGS National Wildlife Health Center (NWHC) in collaboration with multiple partners conducts research into the ecology of avian influenza virus and surveillance for highly pathogenic avian influenza (HPAI) viruses leading to several significant findings towards early detection and response to HPAI.
Avian Influenza (AI) is a global disease with potential high consequence. Wild birds, in particular certain species of waterfowl and shorebirds, are considered to be the natural reservoirs for avian influenza viruses. These subtypes that naturally occur in wild species usually cause little or no disease. In domestic birds, however, some AI viruses can be more pathogenic and mutation or recombination of a virus acquired from wild birds can increase disease potential. In recent years, spill-back has occurred negatively affecting wild birds.
Avian influenza viruses (AIV) are classified by a combination of two groups of proteins found on the surface of the virus: hemagglutinin proteins (H), of which there are 18 (H1-H18), and neuraminidase proteins (N), of which there are 11 (N1-N11). Additional information on avian influenza viruses are available in the Field Manual of Wildlife Diseases.
AI strains are divided into two groups based on the pathogenicity of the virus, or the ability of the virus to produce disease. Most AI strains are classified as low pathogenic avian influenza (LPAI) and cause few clinical signs in infected birds. LPAI generally does not pose a significant health threat to humans. However, LPAI is monitored because two strains of LPAI— the H5 and H7 strains–can mutate into highly pathogenic forms. On the other hand, highly pathogenic avian influenza (HPAI) strains frequently fatal to birds and easily transmissible between susceptible species.
Highly pathogenic avian influenza outbreaks in domestic poultry cause large economic losses to the U.S. economy. It has been thought that Eurasian strains of avian influenza viruses enter the United States through the Pacific Flyway (Alaska to Baja California) and that this route is the most likely avenue for emerging Eurasian AIV strains to enter North America. However, AIV also frequently infects domestic poultry and wild ducks in Europe and Africa and migrating wild birds that use the east Atlantic flyway may also risk introducing Eurasian strain viruses to North America via this route. With the on-going European outbreaks of HPAI there is a risk of moving these viruses to North America as well.
The USGS National Wildlife Health Center, in collaboration with the National Institutes of Health Centers of Excellence for Influenza Research and Surveillance (CEIRS), the University of Iceland, and other partners, has explored the ecology and movement of AI viruses in the North Atlantic region since 2010. This research has demonstrated the importance of the migratory bird flyways in this region to the intercontinental movement of viruses between Europe and North America. AI viruses from both continents, as well as recombinations of both strains, were isolated in Iceland, sometimes from within a single flock of birds, showing that this region is a hotspot of virus movement and genetic reassortment. These studies also demonstrated the longer-term persistence of portions of these viruses within the North Atlantic avian community.
Highly pathogenic AI viruses have been frequently found in wild and domestic European birds, significantly in 2006, and annually since then. This continued European epizootic increases the risk of HPAIV being transported from Europe to North America as bird populations migrate through the North Atlantic to breeding sites in Greenland and Canada, and highlights the importance of these studies. Stakeholders include federal and state agencies, North Atlantic and European countries, and commercial poultry businesses who have an interest in protecting wildlife and/or domestic animals by identifying the risks of HPAIV entering the United States through North Atlantic wild bird flyways. Significant findings from this research in the North Atlantic include:
HPAI and other influenzas circulate in freshwater waterfowl. It is also possible that sea ducks, which regularly move between continents, could play a role in how HPAI moves and evolves around the world. In collaboration with CEIRS, State Wildlife Agencies, Ducks Unlimited, and hunting guides, the NWHC has conducted surveillance in wild sea ducks in the Northeastern United States, Alaska, Canada, and Iceland over the past 6 years. This research has shown that sea duck avian influenzas often differ from those carried by freshwater ducks. This research is currently defining environmental factors that affect AI transmission in marine environments.
Human, agricultural, and wildlife health depend on each other. Therefore, risk assessment, prediction, and management of wildlife diseases are important for our nation’s health and economy. However, monitoring and evaluating wildlife health is difficult and expensive. This leads to incomplete and biased datasets that are difficult to analyze with traditional methods. A project is underway to develop new statistical and mathematical techniques and package them into user-friendly tools. Some examples of new tools in development are the ability to analyze and interpret complex data, assess risk of future or ongoing disease outbreaks, estimate the effects of disease on individuals, populations, and ecosystems, and evaluate potential management solutions. This project, performed in partnership with the Department of Statistics at the University of Wisconsin-Madison, is broadly applicable to a variety of wildlife diseases, but is currently working on new statistical methods for predicting virus isolation of avian influenzas.
In another study, NWHC reserachers also analyzed the genomes of HPAIV that spread in the United States during 2014-2015 and resulted in over $3 billion in losses to the U.S. poultry industry. As infection and transmission of pathogens in wild birds are difficult to measure during a fast-moving outbreak, the NWHC used cutting-edge modeling techniques to analyze genetic similarity between HPAIVs infecting wild birds and poultry. Analyses indicated that even though the viruses likely evolved in Asia, they easily infected and spread among North American wild birds. The viruses were also able to spread between domestic and wild birds (i.e., spillover). However, the rate of spillover was minor, and the poultry outbreak persisted without need for ongoing transmission from wild birds. Techniques used in this study can also be used to examine transmission and adaptation of avian influenza within waterfowl populations and between waterfowl and poultry.
The USGS National Wildlife Health Center is a member of the U.S. Interagency Steering Committee for Surveillance for Highly Pathogenic Avian Influenza in Wild Birds. The NWHC performs both passive and active surveillance for the detection and monitoring of avian influenza. Check out the Avian Influenza Surveillance page to learn more.
Below are multimedia items related to avian influenza.
Below are publications related to avian influenza.
Below are news stories related to avian influenza.
Some avian influenza, or bird flu, viruses that are able to enter North America from other continents through migrating birds can be deadly to poultry...
Ducks in North America can be carriers of avian influenza viruses similar to those found in a 2016 outbreak in Indiana that led to the losses of...
Updates from the National Wildlife Health Center in December 2016.
Highly pathogenic avian influenza (HPAI), commonly referred to as bird flu, is making its way across North America.
WASHINGTON, Dec. 17, 2014 — The United States Department of Agriculture's (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed the...
The avian flu virus that caused widespread harbor seal deaths in 2011 can easily spread to and infect other mammals and potentially humans.
Northern sea otters living off the coast of Washington state were infected with the same H1N1 flu virus that caused the world-wide pandemic in 2009...
Below are FAQs related to avian influenza.
Avian influenza (AI) is caused by an influenza type A virus that can infect poultry such as chickens, turkeys, pheasants, quail, domestic ducks, geese, and guinea fowl. It is carried by wild waterfowl (ducks and geese) and shorebirds.Learn more: USGS Avian Influenza
While rare, human infections with avian influenza viruses have occurred. The Centers for Disease Control and Prevention considers the risk to the general public from HPAI H5 infections in wild birds, backyard flocks, and commercial poultry, to be low.To date, no humans or other mammals have shown signs of disease from the HPAI viruses found in North America but field personnel handling live or...
Although it is possible for domestic poultry to become infected with avian influenza from direct contact with wild birds, it is more likely that avian influenza viruses are spread indirectly to poultry on contaminated feed, clothing, and equipment.Agricultural agencies encourage producers to prevent wild birds and other wildlife from coming into direct contact with their poultry, and to avoid...
To learn more about the impacts of avian influenza on wild birds and the role wild birds may play in the spread of the virus, experts from government agencies have gathered samples from hundreds of thousands of live-captured, apparently healthy wild birds, hunter-harvested birds, and dead wild birds of all species.Testing methods include analyses of fecal samples and swabs of the bird’s trachea...
Avian Influenza (AI) type A viruses are divided into subtypes based on two proteins on the surface of the virus:Hemagglutinin (HA), of which there are 16 subtypes (H1-H16)Neuraminidase (NA), of which there are 9 subtypes (N1-N9)Many combinations of HA and NA proteins are possible (i.e., H5N1, H5N2, H7N2, H7N8, etc).AI viruses are also classified into two groups based on their ability to produce...
The designation of low or highly pathogenic avian influenza refers to the potential for these viruses to kill chickens. The designation of “low pathogenic” or “highly pathogenic” does not refer to how infectious the viruses may be to humans, other mammals, or other species of birds.Most strains of avian influenza are not highly pathogenic and cause few signs of disease in infected wild birds...
Avian influenza (AI) viruses are classified by a combination of two groups of proteins: hemagglutinin or “H” proteins, of which there are 16 (H1 to H16), and neuraminidase or “N” proteins, of which there are nine (N1 to N9).Many different combinations of “H” and “N” proteins are possible. Each combination is considered a different subtype and can be further broken down into different strains. AI...
Below are partners associated with avian influenza projects.