Bird Flu (Avian Flu)

Bird flu, also known as avian flu, avian influenza and H5N1 (a type A influenza virus), arrived in California in 2022 and is now present in Sonoma County and numerous other counties in the state. Though bird flu does not easily infect humans, those who work with poultry and/or dairy cows are at increased risk and should take steps to protect themselves. Fortunately, there are no known cases of person-to-person transmission and almost all cases of avian flu in humans have been mild.

Where did bird flu come from and who is it affecting?

Bird flu was first recognized in poultry 150 years ago in Northern Italy, so it’s been around for a long time, but irregularly. In more modern times, the H5N1 virus was identified in 1996 in domestic waterfowl in Southern China and caused considerable disruption in that region. In 2020, a new variant of H5N1 (HPAI) was detected in wild birds in Europe and, the following year, it was detected in wild birds in the U.S. and Canada due to bird migration.

Tens of millions of wild birds have died due to HPAI and millions of infected domestic fowl have been culled in the U.S. as well. The virus has also spread to numerous other domestic and wild species, including cows, seals, sea otters, condors, cougars, bobcats, bald eagles, polar bears, and more. Millions of wild animals have died from it. Additionally, domestic cats appear to be at increased risk, both through bird predation and raw milk. The virus still remains rare in humans.

Precautions you can take

While the risk of catching avian flu is very low for most individuals, farmworkers who are regularly exposed to poultry and/or dairy cows are at higher risk, as are people who tend backyard flocks and hunters who handle wild birds. Click here for information on the type of personal protective equipment (PPE) needed in those situations.

Here are precautions everyone should take:

Avoid sick or dead birds. Avoid wild birds even if they don’t look sick, since they can have an infection without symptoms. Report any unusual or suspicious deaths of wild birds to the California Department of Fish and Wildlife »
Do not eat or drink raw milk, meat or cheese. Do not provide them to your pets either. Cats, in particular, are highly susceptible to bird flu and these products can be deadly for them.
Get a seasonal flu vaccine. While a flu shot will not prevent infection with bird flu, it can reduce the risk of getting sick with human influenza. Being infected with both seasonal flu and bird flu at the same time (known as a co-infection) can be very dangerous and allow the viruses to combine in ways that allow it to spread among humans, potentially creating a new pandemic.
Wear gloves if you have to touch surfaces that could be contaminated with things like animal litter or feces, mucus, raw milk, meat or saliva.
Avoid poultry farms and bird markets. If you must visit those places, wear a well-fitting face mask and don’t touch the animals.
Wash your hands thoroughly and often. Use hand sanitizer when soap and water are not available.

What is the State of California doing?

Governor Newsom declared a state of emergency on December 18, 2024 to strengthen the State's response after a number of dairy herds in the state were found to be infected. California has distributed protective gear to dairy farms and workers, and is also working with local, state and federal agencies to monitor avian flu in farm animals and people who work closely with poultry and dairy cows.

The California Department of Food and Agriculture (CDFA) has increased its testing of milk to prevent the spread of bird flu to humans. For more information about raw milk, visit this page.

What is the County of Sonoma doing?

The County of Sonoma is monitoring wastewater on an ongoing basis to detect levels of avian flu and other viruses. The County’s Health Services Department has also been reaching out to the agricultural community with PPE and vaccine clinics to protect the farmworkers and prevent co-infections with both viruses.

While more than one million chickens were culled in Sonoma County in late 2023 due to the avian flu virus, no infected dairy herds have been identified to date. We are striving to keep it that way.

Useful links:

Updated January 29, 2025