Avian Influenza

Last Modified: February 04, 2025
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.

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