Our temperate winter climate is not only appealing to the estimated 39 million people that reside in California; it is also the perfect habitat for the approximately 6 million ducks and geese that migrate south in the fall and winter. This migration of waterfowl follows the “Pacific Flyway” which traverses Alaska to the southern tip of Chile. In addition to the birds, any diseases they may be infected with, including viruses, migrate south in the fall and north in the spring with them. One of the viruses that are endemic in waterfowl is Avian Influenza (AI). Unfortunately for our chickens and other avian pets, many waterfowl are currently carrying the highly pathogenic “version” of this virus, meaning that birds exposed to the virus are very likely to become gravely sick and die.

Avian Influenza cases in California through November 2nd 2022.

Because waterfowl are the primary reservoir of avian influenza it is important that we prevent contact between our pet birds and waterfowl.  In addition, it is important to mitigate contact between any shared environments where virus can persist (in ponds or in waterfowl feces, for example). To reduce the transmission of Avian Influenza, the burden is on us to reduce the risk of transmission of disease to our domestic flocks.

What can you do to protect your flock?

Waterfowl are responsible for the introduction of avian influenza.  However, poor biosecurity practices can help amplify the virus and help sustain the virus in the environment. While the central valley of California is the primary habitat for waterfowl in California, waterfowl can be active in Southern California.  In addition, it is important to note that other avian wildlife can be carriers of AI.

Biosecurity (the prevention of disease from getting on to your farm/coop and causing disease in your birds) is often a significant weakness in backyard poultry.  Here are some recommendations that can mitigate risk with respect to avian influenza transmission:

  • House birds away from open water sources. Discourage your birds from interacting with wild birds and vice versa by confining your birds to their coop/enclosure. If not possible, consider having a rigorous cleaning routine to prevent your birds from interacting with fomites (objects that may have viable virus on them) left behind by wild birds.
  • Do not share/exchange animals, equipment or fed with fellow bird owners. At times, restricting access to your birds altogether may be necessary.
  • If contact with waterfowl is made, thorough cleaning and disinfection of clothing, shoes and vehicles used during contact with waterfowl is crucial for preventing the spread of disease onto your farm. If you hunt waterfowl, this is a must follow practice.
  • Have designated clothing and boots that you leave at the entrance to your flock’s area (e.g. garage, back porch, shed) and change into when interacting with your backyard flock as opposed to using those same clothes and shoes when traveling outside your home and potentially transmitting disease. If you hunt waterfowl, make sure your equipment and clothing are separate from your domestic poultry. Change your clothes and disinfect your shoes when returning from feedstores and other locations visited by other bird owners.
  • Always obtain birds from reputable disease-free sources that practice good biosecurity methods and purchase feed from clean dependable suppliers. Store the feed in containers that are bird, rodent, and insect proof. Provide clean fresh water to your birds at all times. When obtaining birds isolate them away from other birds for 30 days before adding them into your flock. This will reduce the risk of introducing disease into the original flock.
  • Fast identification is essential toward controlling an outbreak of AI. If you have a high mortality event that can’t be explained by predators, immediately contact your veterinarian or the Sick Bird Hotline 866-922-BIRD (2473).
  • Use the California Animal Health and Food Safety Laboratory System (CAHFS) to identify why your birds are sick or dead.  The CAHFS lab is a full service diagnostic lab.  You can find more information out at cahfs.ucdavis.edu.
  • Work with your veterinarian, state/federal veterinarian, local university, farm advisor etc. Many of these resources are free!Diagram showing avian influenza spread from waterfowl to domestic birds.

Are Humans at Risk?

While Influenza A viruses (i.e. Avian Flu) can affect many mammals including humans, the current version of HPAI in North America does not currently appear to be infectious to humans. However, historically sporadic human infections with avian flu viruses have occurred primarily and is biologically plausible.  Regardless, maintaining good biosecurity, common sense and good hygiene are essential toward reducing risk of disease transmission for your flock and you!


Written by Dr. Maurice Pitesky at the UC Davis School of Veterinary Medicine.