Avian Influenza (Bird Flu)

This page provides information about avian influenza for employers and workers. Visit the CDC Avian Influenza webpage for current situation information.

close up of young broilers

Photo credit: U. S. Department of Agriculture

Avian influenza (or bird flu) is a disease of birds caused by infection with avian influenza A viruses. Infected birds shed bird flu virus in their saliva, mucous, and feces. People rarely get bird flu; however, human infections with bird flu viruses can happen if enough virus is inhaled or gets into a person’s mouth, eyes, or nose. Bird flu infections happen most often after someone has close, prolonged and unprotected (no gloves or other personal protective equipment) contact with infected birds and then touches their mouth, eyes, or nose.

Domestic poultry may be infected with highly pathogenic avian influenza (HPAI) A viruses or low pathogenic avian influenza (LPAI) A viruses:

  • The highly pathogenic viruses spread quickly and may kill nearly an entire poultry flock within 48 hours.
  • The low pathogenic viruses may not cause symptoms or may cause only mild symptoms such as ruffled feathers or a drop in egg production.

The classification of low pathogenic or highly pathogenic avian influenza A virus refers to the ability of the virus to cause disease in chickens in the laboratory, not in humans. Human infection with low pathogenic and highly pathogenic avian influenza A viruses have resulted in a range of symptoms from mild to severe.

Avian influenza A viruses are a public and occupational health concern for several reasons, including:

  • Some of these viruses have passed sporadically from poultry to humans and caused serious illness and death.
  • They may change into a form that is highly infectious in humans and spreads easily from person to person.
  • As these viruses threaten domestic poultry throughout the world, they are also a risk to workers worldwide who have contact with poultry.
Page last reviewed: May 2, 2022