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Highly Pathogenic Avian Influenza

thumbnail of USGS map showing distribution of Highly Pathogenic Avian Influenza H5 and H5N1 in North America, 2021-2022. - Click to open in larger window
Map- Distribution of Highly Pathogenic Avian Influenza H5 and H5N1 (click to enlarge).
Avian influenza is an infectious disease of birds caused by type A influenza viruses. These viruses naturally circulate among waterfowl and other waterbirds. Viruses are classified based on two surface proteins, Hemagglutinin (H) and Neuraminidase (N), which combine to form different subtypes (e.g., H5N1, H5N2, H7N3). Virus subtypes can be further broken down into different strains which generally circulate within a migratory flyway or geographic area. Signs of infection in wild birds may range from none to severe, and is in part, dependent upon the species of wild bird and virus subtype and strain. Avian influenza viruses are further classified as highly pathogenic (HP) or low pathogenic (LP) based on their ability to cause disease in domestic poultry. Historically, viruses of H5 and H7 subtypes have been more likely to become highly pathogenic.

In December 2021, highly pathogenic avian influenza (HPAI) H5N1 of Eurasian-lineage was detected in domestic poultry and wild birds along the Atlantic coast of Canada. In January and February 2022, detections were made for the first time in wild birds and domestic poultry in the eastern United States. Following its initial detection, the virus has spread to nearly every state with numerous detections in both domestic poultry and wild birds. Prior to its detection along the Atlantic coast, Eurasian HPAI H5N1 activity had been on the rise across Europe in domestic poultry and wild birds since October 2021. In the U.S., detections have been made during surveillance in apparently healthy hunter-harvested and live-sampled waterfowl, as well as in sick and dead waterfowl and other wild birds found individually or during mortality events. Although avian influenza viruses naturally circulate among waterbirds, the strain of H5N1 currently in circulation in the U.S. and Canada has been causing illness and death in a higher diversity of wild bird species than during previous avian influenza outbreaks. The virus also remains highly contagious for domestic poultry. Avian predators and scavengers may be exposed to avian influenza viruses when feeding on infected waterfowl or foraging in areas heavy contaminated with virus shed by waterfowl. Infection with avian influenza viruses among songbirds, including many common backyard birds, appears to be relatively uncommon but more study is needed.

The Wildlife Health Lab in coordination with regional staff and other partners are monitoring wild bird populations for signs of illness. The Wildlife Health Lab continues to investigate mortality events, especially those involving 5 or more wild birds, and conduct surveillance testing for avian influenza. Additionally, CDFW supports the national HPAI surveillance plan for avian influenza testing in hunter-harvested waterfowl and live-birds led by the U.S. Department of Agriculture. For more information please see the CDFW Highly Pathogenic Avian Influenza Information Sheet (PDF)(opens in new tab).

Report a Dead Bird(opens in new tab)

Frequently Asked Questions

Where has HPAI been detected in wild birds in California?

Map of California counties with detections in wild birds.

California counties with detections in wild birds and domestic birds is available from the California Department of Food and Agriculture.

Distribution of Highly Pathogenic Avian Influenza in North America, 2021/2022, maps available from the U.S. Geological Survey National Wildlife Health Laboratory.

The official list of detections in wild birds and domestic birds in the United States is available from the U.S. Department of Agriculture.

Are humans at risk of infection with avian influenza?

The Center for Disease Control states that the risk to the general public’s health from the current H5N1 viruses is low, however, some people may have job-related or recreational exposures to birds that put them at higher risk of infection (CDC 3/7/2022 update). For protective actions for human health, see the CDC website.

How does avian influenza spread?

The virus is shed in bodily fluids such as respiratory droplets, saliva, and feces. Transmission may occur directly from bird to bird, or indirectly through people, animals, or objects contaminated with virus particles (e.g., rodents, insects, feathers, feed, water, clothing, footwear, vehicles).

What can you do to prevent disease spread?

While the risk of HPAI infection among backyard songbirds appears rare, feeding and providing water to wild birds is discouraged especially if backyard poultry or other captive birds are present (e.g., chickens, turkeys, peafowl, ducks, geese, pigeons, doves). Providing food and water to wild birds encourages birds of different species to come into closer and more prolonged contact with one another than is typical when they feed on natural food items. Increased concentration of wild birds at feeders and bird baths may lead to local contamination of the environment with fecal material, which may aid in disease transmission. Wild birds should be excluded from entering enclosures for domestic and pet birds, and food and water should not be shared between wild birds and domestic or pet birds.

If recreating outdoors in areas with large concentrations of waterfowl and other waterbirds, please take care to wash clothing and disinfect footwear and equipment before traveling to other areas or interacting with domestic or pet birds. Footwear and equipment may be washed with soap and water, then disinfected in household bleach diluted 1:10 with water for at least 10 minutes.

Is it okay to dispose of a dead wild bird on my property?

Please report dead wild birds to the WHL’s mortality reporting system.

Where it can be done so safely, dispose of dead birds to help reduce exposure to new birds and minimize scavenging by birds and mammals that also may be susceptible to infection. The CDC recommends using standard protective gear (e.g., impermeable gloves, a medical facemask, and eye protection), and to wash hands with soap and water after disposing of birds. It’s also recommended to change clothes before having contact with domestic or pet birds. Always use disposable gloves, inverted plastic bag and/or shovel to limit contact with the dead bird.

Disposal options may vary by city and county. For questions about dead animal disposal, please contact your county’s environmental health department.

  • Incinerate: Carcass may be incinerated. Contact your local animal services agency. They may be able to dispose or incinerate carcasses. Services vary by location and there may be a charge.
  • Burial: Carcass may be buried (3 feet minimum to prevent scavenging). Regulations vary by location.
  • Landfill: Carcass may be double-bagged and placed in the regular garbage collection. Spray outer bag with 10% bleach solution. Regulations and landfill services vary by location.

Where can I report sick and dead domestic birds?

Sick and dead poultry, domestic ducks, and pet birds may be reported to the California Department of Food and Agriculture’s (CDFA) hotline at 1 (866) 922-2473. For guidance on keeping domestic birds healthy, please visit the CDFA and USDA websites.

What can I do about sick wild birds?

Unfortunately, many birds that develop clinical infection with HPAI will die from the disease. There are no treatments or vaccinations available. Before transporting potentially sick birds to wildlife rehabilitation centers, veterinary clinics, or other animal facilities, contact the facility for guidance and to determine if the bird should be collected. These animal facilities often have other wild birds or domestic birds in their facility and want to minimize the risk of introducing diseases into the facility. If the facility cannot take the bird, it should be left where it is. Do not bring potentially sick wild birds home or move sick birds to another location.

What are recommendations for individuals that may handle wild birds?

HUNTERS: Do not handle or consume sick game. Field dress and prepare game outdoors or in a well-ventilated area. Wear rubber or other disposable gloves while handling and cleaning game. After handling game, wash hands with soap and water, and clean knives, equipment, and surfaces that came into contact with game. Do not eat, drink, or smoke while handling game. All game should be cooked to an internal temperature of 165˚F before consuming. See USDA’s guidance for hunters (PDF) for more information.

FALCONERS: Raptors can become infected with avian influenza viruses from feeding on an infected bird. As a precaution, falconers should avoid hunting wild waterfowl and other waterbirds during the HPAI outbreak. To protect the health of your bird, avoid contact with other captive or pet birds, poultry, free-ranging wild birds, and practice good biosecurity. Consult with a veterinarian if your bird shows signs of illness.

GAME BIRDS FACILITIES: Game birds such as turkeys, pheasants, chukar, and quails, may be susceptible to infection with HPAI. To protect the health of captive birds, practicing good biosecurity is essential. Game birds should not be allowed to mix with domestic poultry or waterfowl. Wild birds should be excluded from enclosures and should not be allowed to share food or water with captive game birds.

WILDLIFE REHABILIATORS: Develop a facility-specific plan to address biosecurity measures, intake protocols, and protection of ambassador animals. During an active outbreak, facilities may wish to consider restricting the admission of certain wild bird species.

Additional resources

What disinfectants are approved for avian influenza viruses?

The Environmental Protection Agency has a list approved disinfectants: Go to http://www.epa.gov and search “avian influenza disinfectants.”