Avian Influenza

Last Modified: July 08, 2024
White chicken standing in a field

Avian influenza, or "bird flu," is a contagious viral disease of domestic and wild birds. It's a major threat to the poultry industry, animal health, trade, and the economy worldwide.

Caused by influenza type A viruses, the disease varies in severity depending on the strain and species affected. Highly pathogenic avian influenza (HPAI) strains are deadly to domestic poultry and can wipe out entire flocks within a matter of days. Low pathogenicity avian influenza (LPAI) strains typically cause few or no signs of illness. They occur naturally in wild birds around the world. However, some LPAI strains can become highly pathogenic in poultry.

Note: Avian influenza A viruses rarely infect people. For more information on human health and avian influenza, visit the Centers for Disease Control and Prevention.

Highly Pathogenic Avian Influenza

  • Sudden death without any prior symptoms of illness
  • Lack of energy and appetite
  • A drop in egg production or soft-shelled, misshapen eggs
  • Swelling of the eyelids, comb, wattles, and shanks
  • Purple discoloration of the wattles, comb, and legs
  • Gasping for air (difficulty breathing)
  • Nasal discharge, coughing, sneezing
  • Twisting of the head and neck (torticollis)
  • Stumbling or falling down
  • Diarrhea

Low Pathogenicity Avian Influenza

LPAI-infected poultry usually don't show any signs of illness. If they do, you may see mild to severe respiratory distress, lack of energy and appetite, decreased egg production, and diarrhea.

Avian influenza viruses spread through direct, bird-to-bird contact. They can also spread via contaminated surfaces or materials, such as manure; egg flats, crates, or other farming materials and equipment; and people's clothing, shoes, or hands.

Biosecurity is key to protecting your flock. Learn more about the simple steps you can take:

Highly Pathogenic Avian Influenza

There is no treatment for HPAI. The only way to stop the disease is to depopulate all affected and exposed poultry.

If your farm is ever affected by HPAI, you’ll need to know what to expect during the response process. We put together a series of materials to help you understand the steps we’ll take and your responsibilities at each stage.

Low Pathogenicity Avian Influenza

Because LPAI does not typically kill poultry the way HPAI does, there may be control options beyond depopulation. For example, quarantine or controlled marketing may also be appropriate.

If your farm is ever affected by LPAI, Federal and State officials will work with you to determine what options are available.

Report Signs of Animal Disease

Producers or owners who suspect an animal disease should contact their veterinarian to evaluate the animal or herd. Find an accredited veterinarian.

Animal health professionals (veterinarians; diagnostic laboratories; public health, zoo, or wildlife personnel; and others) report diagnosed or suspected cases of nationally listed reportable animal diseases to APHIS Area Veterinarians in Charge and to the State animal health official as applicable under State reporting regulations. 

Controlling Avian Influenza

APHIS works closely with States and the poultry industry to prevent avian influenza from becoming established in the U.S. poultry population. Our work takes place on a number of fronts.

Prevention and Control

APHIS cooperates with States, industry, and others to carry out avian influenza prevention and control programs. These programs provide uniform standards  to prevent and control H5/H7 avian influenza in flocks of all sizes, including commercial flocks, household flocks, and live bird markets. APHIS coordinates the programs and provides resources to help States implement standards.

Emergency Preparedness and Response

We respond quickly to contain and eliminate avian influenza when findings occur. With LPAI detections, APHIS provides expertise, funding, and support personnel to States. Each U.S. State and Territory should have an Initial State Response and Containment Plan (sometimes referred to as an ISRCP or Low Path Plan) that indicates procedures for responding to an LPAI detection. Information regarding the ISRCP can be obtained by working with a Poultry Health or National Poultry Improvement Plan  team member.

With HPAI detections, APHIS coordinates the emergency response, working closely with Federal, State, Tribal, and industry partners.

Visit HPAI Emergency Response for more information.

Import Restrictions

APHIS maintains trade restrictions on the import of poultry and poultry products from countries and/or regions affected by avian influenza. We also work closely with the U.S. Department of Homeland Security (DHS) to monitor for illegally smuggled poultry and poultry products. In addition, APHIS quarantines and tests all imported live birds* to ensure they are free of avian influenza before entering the country.

*Except from Canada, which must have appropriate permits

Surveillance in Domestic Poultry

APHIS works closely with Federal, State, and industry partners to monitor U.S. poultry populations for avian influenza. Our surveillance targets several key areas: the live bird marketing system, commercial breeding and production flocks, and backyard flocks.

Because wild birds can carry avian influenza and not appear sick, APHIS works with other Federal and State partners to conduct surveillance testing on wild birds. These tests tell us whether any HPAI viruses—or influenza viruses that could mutate into highly pathogenic strains—are found in the wild bird population.

Wild Bird Plans

To learn more, visit our National Wildlife Disease Program and Wild Bird Avian Influenza Surveillance dashboard.

Send an email to aphisweb@usda.gov to request copies of Wild Bird Avian Influenza Surveillance Data reports and HPAI Findings in Wild Birds reports produced between 2015 and 2021.