In mid-December 2014, two highly pathogenic avian influenza (HPAI) virus strains were confirmed in Washington State, adjacent to an area in British Columbia, Canada where HPAI H5N2 was first detected in commercial poultry. Viral strains confirmed in Whatcom County, Washington, in wild birds included an HPAI H5N2 virus in northern pintails and mallards and HPAI H5N8 virus in American wigeon. Highly pathogenic avian influenza virus H5N8 shares a number of genes with HPAI H5N2, and more importantly, is essentially identical to other HPAI H5N8 strains recently reported in Asia and Europe in commercial poultry and wild birds. These two HPAI strains (H5N8 and H5N2) have subsequently been detected in wild birds, backyard poultry, and commercial poultry in additional states in the U.S. Another HPAI virus strain, a new genetically reassorted H5N1 virus belonging to the same group as the H5 viruses described above was recently detected in North America in wild birds and poultry. This newly discovered H5N1 virus incorporates genes from both Asian and North American avian influenza viruses, making it genetically different from the Asian strain of H5N1 HPAI. For more information on avian influenza and migratory birds, visit the USGS National Wildlife Health Center website at http://www.nwhc.usgs.gov/.
- What is 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, as well as migratory waterfowl, and less commonly, mammals (pigs, horses, cats, and marine mammals). Migratory waterfowl and shorebirds are considered the natural reservoirs and it spreads through contact with feces, saliva, and nasal discharges from infected animals as well as through contaminated water bodies.
- What does low pathogenic/highly pathogenic mean?
The designation of low or highly pathogenic avian influenza refers to the potential for these viruses to cause disease or 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. However, in poultry, some low-pathogenic strains can mutate into highly pathogenic avian influenza strains that cause contagious and severe illness or death among poultry, and sometimes among wild birds as well.
- 3. How are influenza type A viruses classified and what do the different numbers next to the "H" and the "N" designations mean?
Avian influenza viruses are classified by a combination of two proteins, hemagglutinin (H) and neuraminidase (N), which are found on the surface of the virus. These proteins determine important properties of the viruses, such as the species the virus can infect and its resistance to vaccines. There are 144 theoretical combinations of the 16 different H (H1 - H16) and 9 different N (N1 - N9) proteins that make up the subtypes of avian influenza. Each combination is considered a different subtype, and can be further broken down into different strains. AI viruses are further classified by their pathogenicity (low or high) indicating the ability of a particular virus strain to produce disease in domestic chickens.Thus, even though viruses may be named with the same “H" and “N" types, they are not necessarily the same. For example, HPAI H5N1 was recently detected in North America, but this virus differs from the HPAI H5N1 that has been circulating in Asia, Europe, and Africa since it was first detected in 1996.
Highly pathogenic avian influenza viruses in poultry are usually H5 or H7 subtypes of avian influenza, although low pathogenic forms of these H5 and H7 viruses also exist.
- 4. Can you tell me more about the new highly pathogenic avian influenza virus strains that have been recently identified in the United States?
The H5N8 virus originated in Asia and spread rapidly during 2014; it was first detected in Europe and western North America at the end of 2014. HPAI H5N8 is descended from the HPAI H5N1 virus that first emerged in 1996 and has now evolved into multiple distinct sublineages. The H5N8 virus belongs to a sublineage called clade 126.96.36.199 and shares two (of eight) RNA gene segments from the original H5N1. The other six RNA segments are from other avian influenza viruses circulating in Asia.
H5N2 and H5N1
The H5N8 virus has mixed with North American avian influenza viruses creating new mixed-origin viruses, H5N2 and H5N1. These mixed-origin viruses contain the Eurasian hemagglutinin gene (the H5 part of the virus) which contributes to the high pathogenicity (causes significant disease or death) of the virus in poultry. The neuraminidase gene (the N part of these viruses) was introduced from North American low pathogenic avian influenza viruses to create these new viruses. The new viruses are called EA/AM H5 viruses because they contain Eurasian (EA) and North American (AM) viral genetic materials. Thus, this new EA/AM H5N1 virus is not the same as the H5N1 virus found in Asia, Europe, and Africa that has caused human illness and death.
The new EA/AM H5N2 virus was first detected in commercial poultry by Canadian agriculture authorities. Subsequently, H5N2 has been detected in wild birds in Washington, Oregon, California, Nevada, Utah, Idaho, and Wyoming [new states will be added as needed]. As of early 2015, the H5N1 virus has only been detected twice, the first time in a wild duck sampled in Washington and subsequently in backyard poultry in British Columbia, Canada. None of these viruses is known to have caused disease in humans or other mammals, and detailed analyses of these viruses are ongoing in cooperation with the U.S. Department of Agriculture, the Centers for Disease Control and Prevention, and other laboratories.
- What do falconers and staff members at wildlife rehabilitation centers need to know about recent outbreaks of HPAI?
The first detection of HPAI H5N8 in North America was in dead captive gyrfalcons in Washington. The gyrfalcons likely became infected with HPAI H5N8 after they were fed meat from waterfowl unknowingly infected with the virus. Subsequently, two other premises with captive raptors have reported mortality-in gyrfalcons and a great-horned owl-caused by HPAI. It is recommended that meat from raw wild game, especially from waterfowl, not be fed to captive raptors. Falconers should also be cautious of hunting wild waterfowl with their birds; state agencies and falconry organizations are recommending against doing so
(for examples, see "http://www.wafalconers.org/" and "http://www.dfw.state.or.us/wildlife/license_permits_apps/falconry/").
- What do wildlife biologists, hunters, and others who come in contact with wildlife need to be concerned about with regards to these findings?
Although no human infections from these viruses have been documented to date, there is limited information about the risk that these HPAI viruses may pose to humans. If you handle live or dead animals, you should take basic precautions to protect yourself against potential pathogens and to prevent spread of any diseases to other people or animals. These precautions include wearing disposable gloves (made of nitrile or other barrier material) and changing them regularly, washing hands with soap thoroughly after handling animals, not eating, drinking, or smoking in areas where animals are handled, and disinfecting work surfaces both during and after use. For more information, please see this CDC site: "Avian Influenza A Virus Infection in Humans".
- Are there any precautions I need to take to limit the risk of infection to pet birds or backyard poultry?
For more information on keeping pet birds and backyard poultry safe, please see this USDA site:"Biosecurity for Birds". If you handle live or dead animals, you should take basic precautions to protect yourself against potential pathogens and to prevent spread of any diseases to other people or animals. These precautions include wearing disposable gloves (made of nitrile or other barrier material) and changing them regularly, washing hands with soap thoroughly after handling animals, not eating, drinking, or smoking in areas where animals are handled, and disinfecting work surfaces both during and after use.
- What species of wild birds have been affected and how?
In North America, HPAI viruses have been found in a variety of species of dabbling ducks including mallard, northern pintail, American wigeon, northern shoveler, gadwall, green-winged teal, and wood duck, as well as in Canada geese. In addition, HPAI viruses have also been found in various species of raptors in North America, including gyrfalcon, peregrine falcon, red-tailed hawk, Cooper's hawk, bald eagle, and great-horned owl. While we know these avian influenza subtypes-H5N2, H5N8, and H5N1- can infect several species of waterfowl and raptors, there is some evidence that some waterfowl may be carriers of HPAI viruses and some raptors may die due to infection with HPAI viruses. We do not know the potential impact on these species without further scientific studies. Globally, the H5N8 virus (or reassorted viruses closely related to H5N8 virus) has been identified in carcasses from a number of other wild bird species, including cranes, egrets, ibises and storks, geese, swans, ducks (additional to those species listed above), and song birds.
- Should I take any precautions as I move boats/equipment between wetlands?
It is possible to transport avian influenza viruses on boats, waders, or other equipment moved between wetlands, especially if the equipment was not given the opportunity to dry (flu viruses degrade quickly when they dry) between sites. It is advisable to always disinfect field equipment when moving it between field sites, not only to prevent the spread of infectious diseases but also to prevent the spread of exotic or invasive species of plants and animals. Your state may have specific guidelines on preventing the spread of invasive species. The Wisconsin Department of Natural Resources, for example, provides this"Web page"about preventing spread of invasive species in aquatic environments.
- Are there any outward signs that a hunter-killed duck may be infected with highly pathogenic avian influenza?
There is no way to tell by just looking at a hunter-killed bird whether it is infected with HPAI. However, if a hunter-killed duck or any other game animal appears sick, either based upon observation of unusual behavior before it was shot or because of the way it looks when you are preparing it, it is advised that you do not consume the animal or feed it to other animals. Please note that all game should be thoroughly cooked to an internal temperature of 165 degrees F. For additional guidance for hunters, please see: "Guidance for Hunters - Protect Yourself and Your Birds from Avian Influenza"
- Where can I find more information about the recent HPAI outbreaks?
To learn more about these outbreaks, please refer to these National Wildlife Health Center (NWHC) Wildlife Health Bulletins: "Detection of Novel Highly Pathogenic Avian Influenza Viruses in Wild Birds" and "Detection of Highly Pathogenic Avian Influenza Viruses H5N2 and H5N8 in Wild Birds of the United States". Also see this article published in Emerging and Infectious Diseases: "Novel Eurasian Highly Pathogenic Influenza A H5 Viruses in Wild Birds, Washington, USA, 2014".
- Where can I see summarized lists of results from combined federal and state agency HPAI surveillance in wild birds, captive wild birds and poultry?
For an up-to-date summary of results from combined federal and state agency HPAI virus surveillance in wild birds, view this table: "Wild bird HPAI cases in the U.S." For surveillance results for HPAI in poultry and captive wild birds, view this USDA APHIS table: "Update on Avian Influenza Findings".
Additional information on avian influenza from the USDA is available at this "Avian Influenza Disease page".
Other sources of information about avian influenza
USDA - "Biosecurity for Wild Birds, Pet Birds and Poultry"
CDC - "Workplace Safety and Health Topics - Avian Influenza"