Distribution of Highly Pathogenic Avian Influenza H5 and H5N1 in wild birds the United States, by county, 2021-2025. Updated February 10, 2025.
What is Avian Influenza?
Avian influenza (AI) is caused by influenza type A viruses that historically have spread between wild birds (waterfowl and shorebirds) with occasional outbreaks in poultry (chickens, turkeys). These viruses can change over time and there has been a fundamental change with AI viruses now causing illness and death in wild birds, wild mammals, poultry, dairy cattle, cats, and people.
Learn more:
- Current Bird Flu Situation (Centers for Disease Control)
- USGS science on avian influenza
Related
What causes chronic wasting disease?
Chronic wasting disease is caused by a misfolded protein called a prion. All mammals produce normal prions that are used by cells, then degraded and eliminated, or recycled, within the body. When disease-associated prions contact normal prions, they cause them to refold into their own abnormal shape. These disease-associated prions are not readily broken down and tend to accumulate in--and damage-...
What are the visual signs of chronic wasting disease?
Chronic wasting disease (CWD) has an extended incubation period averaging 18–24 months between infection and the onset of noticeable signs. During this time frame animals look and act normal. The most obvious sign of CWD is progressive weight loss. Numerous behavioral changes also have been reported, including decreased social interaction, loss of awareness, and loss of fear of humans. Diseased...
What is chronic wasting disease?
Chronic wasting disease (CWD) is a fatal, neurological illness occurring in North American cervids (members of the deer family), including white-tailed deer, mule deer, elk, and moose. Since its discovery in 1967, CWD has spread geographically and increased in prevalence locally. CWD is contagious; it can be transmitted freely within and among cervid populations. No treatments or vaccines are...
What is White-nose Syndrome?
White-nose syndrome is an emergent disease of hibernating bats that has spread from the northeastern to the central United States at an alarming rate. Since the winter of 2007-2008, millions of insect-eating bats in at least 40 states and eight Canadian provinces have died from this devastating disease. The disease is named for the white fungus, Pseudogymnoascus destructans, that infects skin of...
Does White-nose Syndrome pose a risk to human health?
Thousands of people have visited affected caves and mines since White-nose Syndrome (WNS) was first observed, and there have been no reported human illnesses attributable to WNS. We are still learning about WNS, but we know of no risk to humans from contact with WNS-affected bats. However, we urge taking precautions and not exposing yourself to WNS. Biologists and researchers use protective...
What should cavers know and do in regard to White-nose Syndrome?
In response to White-nose Syndrome (WNS), the U.S. Fish and Wildlife Service and individual states request that cavers observe all cave closures and advisories, and avoid caves, mines or passages containing hibernating bats to minimize disturbance to them. The Service asks that cavers and cave visitors stay out of all caves in the affected states and adjoining states to help slow the potential...
What should I do if I find dead or dying bats, or if I observe bats with signs of White-nose Syndrome?
If you find a dead or dying bat: Contact your state wildlife agency, file an electronic report in those states that offer this service, e-mail U.S. Fish and Wildlife Service biologists in your area or contact your nearest Fish and Wildlife Service field office to report your potential White-nose Syndrome (WNS) observations. It is important to determine the species of bat in case it is a federally...
Can people get avian influenza?
While rare, human infections with avian influenza viruses have occurred. The Centers for Disease Control (CDC) consider the risk to the general public from infections to be low. There have been human cases associated with the dairy cattle and wild bird strains of HPAI. To date, most human cases have been associated with farm workers (poultry and dairy cattle operations) as well as people who have...
Can wild birds spread avian influenza to domestic poultry?
Wild birds can directly or indirectly spread avian influenza to domestic poultry. The indirect route is likely most common due to viral contamination of the farm environment (feed, equipment, boots, clothes). The U.S. Department of Agriculture has found that farm-to-farm movement is also a major route for avian influenza spread, noting that farm biosecurity is critical to reduce the risk of avian...
How do scientists know if individual wild birds are infected with avian influenza?
The U.S. Department of Agriculture implements a plan every year to monitor wild birds for highly pathogenic avian influenza. This national plan could not be implemented without the engagement of State partners, the National Flyway Council, the Department of the Interior, and other agencies. This coordinated effort is revised annually based on new science and data shared through the Interagency...
What are the different types of avian influenza? What do the numbers next to H and N mean?
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, for example H5N1, H5N2, H7N2, and H7N8. AI viruses are also classified into two groups based on their ability to...
Distribution of Highly Pathogenic Avian Influenza H5 and H5N1 in North America, 2021-2025
Distribution of Highly Pathogenic Avian Influenza H5 and H5N1 in wild birds the United States, by county, 2021-2025. Updated February 10, 2025.
Visual History of Worldwide Avian Influenza Outbreaks
For more information on avian influenza, see http://www.pwrc.usgs.gov/ai.
For more information on avian influenza, see http://www.pwrc.usgs.gov/ai.
Blue-winged teal in Texas. Inset shows avian influenza virus
Blue-winged teal in Texas. Inset shows avian influenza virus
Blue-winged teal in Texas. Inset shows avian influenza virus
NWHC technician preparing avian samples for avian influenza testing
USGS National Wildlife Health Center laboratory technician preparing avian samples for avian influenza testing.
USGS National Wildlife Health Center laboratory technician preparing avian samples for avian influenza testing.
Sampling Forster’s Tern Chicks for Avian Influenza Study
Scientists sampling Forster's Tern chicks for avain influenza during salt pond restoration work in south San Francisco Bay salt ponds.
Scientists sampling Forster's Tern chicks for avain influenza during salt pond restoration work in south San Francisco Bay salt ponds.
What are the differences between low pathogenic and highly pathogenic avian influenza viruses and how are influenza viruses grouped?
linkListen to hear the answer.
Testing for Avian Influenza
A USGS scientist takes a sample from a northern pintail duck (Anas acuta) to be tested for avian influenza.
A USGS scientist takes a sample from a northern pintail duck (Anas acuta) to be tested for avian influenza.
USGS biologists swab a hen mallard duck for avian influenza
USGS biologists swab a hen mallard duck for avian influenza in Rio Grande County, Colorado.
USGS biologists swab a hen mallard duck for avian influenza in Rio Grande County, Colorado.
Related
What causes chronic wasting disease?
Chronic wasting disease is caused by a misfolded protein called a prion. All mammals produce normal prions that are used by cells, then degraded and eliminated, or recycled, within the body. When disease-associated prions contact normal prions, they cause them to refold into their own abnormal shape. These disease-associated prions are not readily broken down and tend to accumulate in--and damage-...
What are the visual signs of chronic wasting disease?
Chronic wasting disease (CWD) has an extended incubation period averaging 18–24 months between infection and the onset of noticeable signs. During this time frame animals look and act normal. The most obvious sign of CWD is progressive weight loss. Numerous behavioral changes also have been reported, including decreased social interaction, loss of awareness, and loss of fear of humans. Diseased...
What is chronic wasting disease?
Chronic wasting disease (CWD) is a fatal, neurological illness occurring in North American cervids (members of the deer family), including white-tailed deer, mule deer, elk, and moose. Since its discovery in 1967, CWD has spread geographically and increased in prevalence locally. CWD is contagious; it can be transmitted freely within and among cervid populations. No treatments or vaccines are...
What is White-nose Syndrome?
White-nose syndrome is an emergent disease of hibernating bats that has spread from the northeastern to the central United States at an alarming rate. Since the winter of 2007-2008, millions of insect-eating bats in at least 40 states and eight Canadian provinces have died from this devastating disease. The disease is named for the white fungus, Pseudogymnoascus destructans, that infects skin of...
Does White-nose Syndrome pose a risk to human health?
Thousands of people have visited affected caves and mines since White-nose Syndrome (WNS) was first observed, and there have been no reported human illnesses attributable to WNS. We are still learning about WNS, but we know of no risk to humans from contact with WNS-affected bats. However, we urge taking precautions and not exposing yourself to WNS. Biologists and researchers use protective...
What should cavers know and do in regard to White-nose Syndrome?
In response to White-nose Syndrome (WNS), the U.S. Fish and Wildlife Service and individual states request that cavers observe all cave closures and advisories, and avoid caves, mines or passages containing hibernating bats to minimize disturbance to them. The Service asks that cavers and cave visitors stay out of all caves in the affected states and adjoining states to help slow the potential...
What should I do if I find dead or dying bats, or if I observe bats with signs of White-nose Syndrome?
If you find a dead or dying bat: Contact your state wildlife agency, file an electronic report in those states that offer this service, e-mail U.S. Fish and Wildlife Service biologists in your area or contact your nearest Fish and Wildlife Service field office to report your potential White-nose Syndrome (WNS) observations. It is important to determine the species of bat in case it is a federally...
Can people get avian influenza?
While rare, human infections with avian influenza viruses have occurred. The Centers for Disease Control (CDC) consider the risk to the general public from infections to be low. There have been human cases associated with the dairy cattle and wild bird strains of HPAI. To date, most human cases have been associated with farm workers (poultry and dairy cattle operations) as well as people who have...
Can wild birds spread avian influenza to domestic poultry?
Wild birds can directly or indirectly spread avian influenza to domestic poultry. The indirect route is likely most common due to viral contamination of the farm environment (feed, equipment, boots, clothes). The U.S. Department of Agriculture has found that farm-to-farm movement is also a major route for avian influenza spread, noting that farm biosecurity is critical to reduce the risk of avian...
How do scientists know if individual wild birds are infected with avian influenza?
The U.S. Department of Agriculture implements a plan every year to monitor wild birds for highly pathogenic avian influenza. This national plan could not be implemented without the engagement of State partners, the National Flyway Council, the Department of the Interior, and other agencies. This coordinated effort is revised annually based on new science and data shared through the Interagency...
What are the different types of avian influenza? What do the numbers next to H and N mean?
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, for example H5N1, H5N2, H7N2, and H7N8. AI viruses are also classified into two groups based on their ability to...
Distribution of Highly Pathogenic Avian Influenza H5 and H5N1 in North America, 2021-2025
Distribution of Highly Pathogenic Avian Influenza H5 and H5N1 in wild birds the United States, by county, 2021-2025. Updated February 10, 2025.
Distribution of Highly Pathogenic Avian Influenza H5 and H5N1 in wild birds the United States, by county, 2021-2025. Updated February 10, 2025.
Visual History of Worldwide Avian Influenza Outbreaks
For more information on avian influenza, see http://www.pwrc.usgs.gov/ai.
For more information on avian influenza, see http://www.pwrc.usgs.gov/ai.
Blue-winged teal in Texas. Inset shows avian influenza virus
Blue-winged teal in Texas. Inset shows avian influenza virus
Blue-winged teal in Texas. Inset shows avian influenza virus
NWHC technician preparing avian samples for avian influenza testing
USGS National Wildlife Health Center laboratory technician preparing avian samples for avian influenza testing.
USGS National Wildlife Health Center laboratory technician preparing avian samples for avian influenza testing.
Sampling Forster’s Tern Chicks for Avian Influenza Study
Scientists sampling Forster's Tern chicks for avain influenza during salt pond restoration work in south San Francisco Bay salt ponds.
Scientists sampling Forster's Tern chicks for avain influenza during salt pond restoration work in south San Francisco Bay salt ponds.
What are the differences between low pathogenic and highly pathogenic avian influenza viruses and how are influenza viruses grouped?
linkListen to hear the answer.
Testing for Avian Influenza
A USGS scientist takes a sample from a northern pintail duck (Anas acuta) to be tested for avian influenza.
A USGS scientist takes a sample from a northern pintail duck (Anas acuta) to be tested for avian influenza.
USGS biologists swab a hen mallard duck for avian influenza
USGS biologists swab a hen mallard duck for avian influenza in Rio Grande County, Colorado.
USGS biologists swab a hen mallard duck for avian influenza in Rio Grande County, Colorado.
Updated Date: April 17, 2025