what wild birds carry bird flu

Wild birds can be infected with highly pathogenic avian influenza (HPAI) and show no signs of illness. They can carry the disease to new areas when migrating, potentially exposing domestic poultry to the virus.

APHIS’ wild bird surveillance program provides an early warning system for the introduction and distribution of avian influenza viruses of concern in the United States, allowing APHIS and the poultry industry to take timely and rapid action to reduce the risk of spread to our poultry industry and other populations of concern.

Captive wild birds, defined by the World Organisation for Animal Health (WOAH) as a wild animal that is captive or otherwise lives under or requires human supervision or control, are included in the numbers reported on this page. Captive wild birds, including sick wild birds that may have died after being found and taken to a rehabilitator or sanctuary, will have the designation of “captive wild bird” in the WOAH Classification column. To remain consistent with current reporting, information will continue to be broken down to the county level. To protect privacy, private or business names will not be released. This is consistent with current reporting of wild birds as well as commercial and backyard flocks.

APHIS is continuing to process samples collected over the past year from State and partner agencies and will continue to post this information on this page. The detection date is the date of National Veterinary Services Laboratories confirmatory testing. APHIS will provide updates below when there are significant differences between sample collection and detection dates.

For submitting agencies who notice data errors or omissions, please send an email with supporting documentation (laboratory report/accession number/data collection) to wslabresults@usda.gov.

Both maps represent samples collected by APHIS Wildlife Services as well as morbidity/mortality samples submitted by State agencies and private facilities. The data presented visually in these maps is also available in the table below.

Date Detected: Specimens detected by the NAHLN H5 assay were further tested by a developmental real-time RT PCR targeting the Eurasian lineage goose/Guangdong H5 clade “Date Detected” indicates the date when a positive detection was obtained by the developmental RRT PCR targeting the Eurasian lineage goose/Guangdong H5 clade

EA = Eurasian; AM = North American; the EA H5 ( viruses are highly pathogenic to poultry.

Virus lineage, subtype, and pathotype per cleavage site analysis are determined from sequence data direct from the sample or virus isolate. An incomplete subtype indicates either (1) the specimen is pending virus isolation and/or sequencing results, or (2) the specimen was detected by the developmental H5 RRT PCR targeting the Eurasian lineage goose/Guangdong H5 clade but could not be further characterized, often due to a low level of virus or viral RNA present in a given sample.

Avian influenza is caused by influenza Type A virus (influenza A). Avian-origin influenza viruses are broadly categorized based on a combination of two groups of proteins on the surface of the influenza A virus: hemagglutinin or “H” proteins, of which there are 16 (H1–H16), and neuraminidase or “N” proteins, of which there are 9 (N1–N9). Many different combinations of “H” and “N” proteins are possible. Each combination is considered a different subtype, and related viruses within a subtype may be referred to as a lineage. Avian influenza viruses are classified as either “low pathogenic” or “highly pathogenic” based on their genetic features and the severity of the disease they cause in poultry. Most viruses are of low pathogenicity, meaning they cause no signs or only minor clinical signs of infection in poultry.

Classification of Bird Flu Viruses Highly Pathogenic and Low Pathogenic Avian Influenza A Viruses

Avian influenza A viruses are classified into the following two categories: low pathogenicity avian influenza (LPAI) A viruses, and highly pathogenic avian influenza (HPAI) A viruses. The categories refer to molecular characteristics of a virus and the virus’ ability to cause disease and mortality in chickens in a laboratory setting [2.55 MB, 64 Pages]. HPAI and LPAI are defined and explained below:

  • Low Pathogenic Avian Influenza (LPAI): These viruses cause mild illness in chickens and poultry, such as ruffled feathers and decreased egg production, or no symptoms at all. The majority of AIVs in birds are not highly pathogenic and infected wild birds show minimal symptoms of illness. Certain viruses that are not as harmful to poultry can mutate into highly dangerous viruses that cause avian influenza.
  • Highly Pathogenic Avian Influenza (HPAI): When poultry are infected with highly pathogenic avian influenza viruses, they suffer from severe illness and have a high death rate. The majority of A(H5) and A(H7) avian influenza viruses that are circulating among birds are LPAI A viruses, whereas only a small percentage are designated as HPAI A viruses. The HPAI A(H5) or A(H7) virus infections can cause a disease that affects multiple internal organs in chickens, often within hours. Mortality rates can reach up to 90% in these cases. However, ducks can be infected without any signs of illness. When wild birds migrate, HPAI A(H5) and A(H7) virus infections in poultry can also spread to those birds, expanding the virus’s geographic range. Certain HPAI A(H5) and A(H7) virus subtypes can infect wild bird species without causing illness, but other subtypes can cause serious illness and even death in some infected wild bird species as well as infected poultry.

The viruses that cause HPAI and LPAI can spread quickly among flocks of chickens. Both LPAI and HPAI A viruses have caused mild to severe illness in infected humans; however, the designations HPAI and LPAI do not relate to or correlate with the severity of illness in cases of human infection with these viruses. The influenza A virus subtypes that usually only infect birds and those that can infect both birds and humans differ in terms of genetics and antigens.

Genetic characteristics allow specific bird flu viruses to be categorized and distinguished from one another. In order to evaluate the genetic characteristics of circulating bird flu viruses, samples are gathered and subjected to a laboratory procedure known as genetic characterization. A phylogenetic tree is a visual representation of the genetic variations among a group of flu viruses. Similar to family (genealogy) trees for humans, phylogenetic trees for flu viruses The trees illustrate the close relationships between different viruses. On the tree, every sequence from a particular flu virus has a branch of its own. These “nodes,” which are where branches converge, stand in for the viruses’ common ancestor and show that their genetic sequences are similar. Another way to think of viruses that are related is as members of the same clade. Clade 2 includes a large number of the H5N1 bird flu viruses that have been linked to infections in poultry and wild birds in the United States. 3. 4. 4b. Visit Influenza Virus Genome Sequencing and Genetic Characterization for more details on influenza virus clades and genetic characteristics.

The influenza type A virus (influenza A) is the cause of avian influenza. Hemagglutinin, or “H” proteins, of which there are 16 (H1–H16), and neuraminidase, or “N” proteins, of which there are 9 (N1–N9), are two groups of proteins on the surface of the influenza A virus that together make up the broad classification of influenza viruses of avian origin. Many different combinations of “H” and “N” proteins are possible. Every combination is regarded as a distinct subtype, and a lineage of related viruses within a subtype is sometimes used. Avian influenza viruses are categorized as either “highly pathogenic” or “low pathogenic” according to the severity of the disease they cause in poultry and their genetic makeup. Most viruses only cause mild or no clinical symptoms of infection in poultry because they have low pathogenicity.

Date Detected: A developmental real-time RT PCR directed towards the Eurasian lineage goose/Guangdong H5 clade 2 was performed on specimens identified by the NAHLN H5 assay. 3. 4. 4b. “Date Detected” is the date on which the developmental RRT PCR that targets the Eurasian lineage goose/Guangdong H5 clade 2 produced a positive detection. 3. 4. 4b.

APHIS will keep updating this page with information about the samples it has been processing from State and partner agencies over the past year. The date of the confirmatory testing conducted by National Veterinary Services Laboratories is the detection date. When there are notable discrepancies between the dates of sample collection and detection, APHIS will post updates below.

The maps display samples gathered by APHIS Wildlife Services in addition to samples of morbidity and mortality provided by private facilities and State agencies. The table below contains the same information that is shown visually in these maps.

Highly pathogenic avian influenza (HPAI) can infect wild birds without causing any symptoms. When they migrate, they can bring the illness with them, possibly exposing domestic poultry to the virus.


Which bird is most affected by bird flu?

Waterfowl, such as swans, ducks, and geese, are the type of birds that are most likely to be infected with avian influenza. Although wild backyard birds and pigeons are unlikely to be infected with avian influenza, it is always best to minimize contact with fecal material.

Do hummingbirds get avian flu?

Hummingbirds are thought to be at lower risk than other birds because their habits and sources of food and water are so different. Nevertheless, I haven’t seen any evidence that hummingbirds are immune to bird flu.

Do doves carry bird flu?

Collectively, results of 32 field studies representing 24 countries across four continents indicate an antibody prevalence of 8.01% in pigeons and doves but only 0.37% of the total was associated with exposure to the same serotype as a highly pathogenic avian influenza (HPAI) outbreak occurring in poultry at the time.

Can squirrels get bird flu?

H5N1 detected in polar bear and squirrel In related developments, APHIS reported two more detections in mammals. These are the first detections since September, when H5N1 was reported in seals from Washington.