Avian Influenza, also known as the bird flu, is caused by influenza Type A virus. Waterfowl like ducks, geese, and shorebirds are carriers of Avian Influenza, especially Highly Pathogenic Avian Influenza or HPAI. With HPAI there’s a higher chance of the virus to be passed on to a specific host—like your backyard chickens, turkeys, and other poultry.


The United States, free flying waterfowl, commercial flocks and backyard farmers of poultry, and other birds are currently battling Highly Pathogenic Avian Influenza. Birds who are exposed are very likely to become sick and die, so what does this virus currently look like in California?


Confirmed Cases and Resources to Track HPAI


Since the Central Valley of California is the primary habitat for waterfowl, there have been many confirmed cases and incidents of Highly Pathogenic Avian Influenza in this area. The California Department of Food and Agriculture produces Avian Influenza updates, and the most recent confirmed case in the Southern California area was in Santa Barbara County on January 26th, 2023. As of today, February 20th, 2024, there have been no detections of HPAI in California in backyard or commercial flocks for this month.


If you would like to track HPAI in commercial and backyard flocks by month, year, and state, please visit the USDA’s 2022-2024 Confirmations.

A map of California counties showing HPAI detections in domestic and wild birds during the 2023-2024 migratory waterfowl season. In Southern California, only Kern and San Diego counties have had HPAI detection, and these have only been in wild birds. Domestic bird cases are focused in the Central Valley, North Bay Area, and Lassen County.

  • This map shows confirmed Highly Pathogenic Avian Influenza in wild birds, domestic birds, and both domestic and wild birds.
  • Please find your county and see if there has been HPAI detected as of December 2023.
  • The USDA Animal and Plant Health Inspection Service and California Animal Health & Food Safety Laboratory System updates these detections here, so please click on the link to get the most accurate information.


Preventing and Reporting HPAI


Implementing and practicing good biosecurity protocols is key to protecting your flock. By housing birds away from open water sources, discouraging them to interact with waterfowl or wild birds, and having designated clothing and boots when working with your flock you can deter HPAI from infecting your poultry. If you would like more information on protecting your flock, please visit Preparing for Highly Pathogenic Avian Influenza in SoCal: Tips and Resources for Backyard Owners, a previous article written and published on the SoCal Nestbox.


The key to addressing Highly Pathogenic Avian Influenza when it does appear is identification and subsequent reporting. Symptoms of birds who are sick and/or may have HPAI include:


  • Trouble breathing
  • Discharge from mouth, eyes, and/or nose
  • Lack of energy
  • Swollen eyes, wattles, head, or comb
  • Sudden death


If you suspect your commercial flock, backyard poultry, or any bird may have Highly Pathogenic Avian Influenza or if you have an unexplained high mortality event, contact your veterinarian or the Sick Bird Hotline at 866-922-BIRD (2473).




To track current Highly Pathogenic Avian Influenza Detections in California by county or specifically in commercial and backyard flocks by year and month, please visit the California Department of Food and Agriculture Avian Influenza Updates. Remember, the impact of HPAI can be prevented, deterred, and reduced by you maintaining good biosecurity and reporting when necessary!



Written by Reena Grewal, University of California, Davis Student.

Edited by Maurice Pitesky and Joseph Gendreau at the UC Davis School of Veterinary Medicine.