What to know about the bird flu outbreak as California declares a state of emergency

California Gov. Gavin Newsom declared a state of emergency Wednesday amid the spread of bird flu across more than a quarter of the state’s dairies in the last month.

The announcement gives California more access to resources to combat the virus, which was detected in California cows in August and has plagued the country’s largest dairy-producing state.

The risk of human infection remains low — 34 California residents were infected since March — and symptoms have mostly been mild, except for a Louisiana resident with a presumptive bird flu case who was hospitalized with “severe” symptoms. California’s cases account for about half of the known human infections across the country.

Still, Newsom’s declaration has riled up concern, particularly in other top dairy-producing states, including Wisconsin and Pennsylvania.

Here’s what to know.

The bird flu is a virus that typically spreads through wild birds, especially waterfowl. Wild birds generally show no signs of the virus even when they are infected, but domestic birds can contract the virus through contact with wild birds or their droppings.

Bird flu is an aggressive form of the disease that is highly contagious, causes serious respiratory and digestive symptoms in domestic birds, and can wipe out entire flocks. Usually, domestic flocks with bird flu are euthanized.

According to the CDC, mammals can be infected with the bird flu when they are exposed to environments — including birds or bird droppings — contaminated with the virus. This can also include eating infected poultry, inhaling virus particles present in the air near infected birds, or drinking water contaminated with virus particles.

What’s different about this outbreak is that herds across the U.S. are getting sick, not just individual animals. It is unclear what has caused the wider spread of the disease.

Symptoms among dairy cattle include eating less, producing less milk, and, occasionally, diarrhea or very dry manure. Most cows will recover within two to three weeks.

By declaring a state of emergency, California is able to allocate more funding to crisis response, in the same way a state would respond to a natural disaster.

Newsom called the move “a targeted action to ensure government agencies have the resources and flexibility they need to respond quickly to this outbreak” since it is spreading rapidly among dairy farms.

The CDC said Wednesday that the risk of bird flu to the public’s health overall remains low.

Sixty-one human cases of bird flu have been reported nationwide. Of those, 37 have been linked to cattle exposure and 34 of the total have been directly linked to the California outbreak.

All but one of the reported cases were contracted by people with connections to a dairy or poultry farm. The exception was a child in the San Francisco Bay Area with mild cold and flu symptoms.

The CDC says people who work closely with animals, such as dairy farm workers, are at higher risk of infection and should wear personal protective equipment.

According to health officials, pasteurized milk remains safe because it is heat-treated to kill the virus.

Still, concerns lie with drinking raw milk. Some raw milk producers have recalled their products after bird flu was detected in retail samples.

No known cases of the bird flu have been found to date in people who drank raw milk, but the U.S. Department of Agriculture has ramped up its testing of raw milk, hoping to better identify the scale of the outbreak.

Raw milk can be purchased in Pennsylvania, and sellers usually subject that milk to tests for bacteria — but not always for the bird flu.

The FDA says consuming eggs is safe.

But the recent uptick of cases has affected their price and availability, especially during the holiday season.

The current bird flu outbreak that began in February 2022 has led to the slaughter of more than 111 million birds, mostly egg-laying chickens. Anytime the virus is found, every bird on a farm is killed to limit the spread of the disease.

More than 6 million birds were slaughtered in November because of bird flu. They were a relatively small part of the total U.S. egg-laying flock of 377 million chickens. Still, the flock is down about 3% over the last year, contributing to a 4% drop in egg production, according to the U.S. Department of Agriculture.

The latest wave of bird flu is scrambling supplies of cage-free eggs because California has been among the hardest-hit states. California, Nevada, Washington, and Oregon all require eggs sold in their states to be cage-free.

Pennsylvania has seen about 70 reports of bird flu outbreaks in birds over the last few years, according to the USDA; in March 2023, the state had more birds with it than anywhere else in the country. That outbreak has subsided in recent months, experts say, but agriculture officials are still on high alert.

So far, Pennsylvania has seen no cases of bird flu in cattle. The closest confirmed cases emerged in Ohio and North Carolina.

Pennsylvania required that cattle from affected states be tested for bird flu before they enter the state prior to a federal directive this week requiring that cattle must test negative for bird flu before moving between states.

A Pennsylvania quarantine order, released earlier this year, also says animals from infected herds cannot move to the state until their farm has been found to be free of the disease.

The Pennsylvania Department of Agriculture and Penn State Extension, the university’s science education arm, have vets and experts on call for farms 24 hours a day for suspected outbreaks.

Last month, the Pennsylvania Department of Agriculture announced it would require precautionary bulk testing of milk for the bird flu at no cost to Pennsylvania farmers. Other states implementing mandatory bulk testing include California, Colorado, Michigan, and Oklahoma.

This article contains information from the Associated Press.