The rise of bird flu across farms in California has raised questions about the virus and and its potential threat to humans. While the threat to humans is currently small, here is what you need to know about the state of bird flu.

On Dec. 18, Gov. Gavin Newsom declared a state of emergency as the H5N1 bird flu virus continues to infect dairy herds across the country — including more than 600 in California, according to state’s Department of Food and Agriculture.

Since April, there have been 61 human cases of avian flu nationwide, according to U.S. Centers for Disease Control and Prevention data.

And in California, there have been 36 confirmed cases of the illness since Friday, Dec. 20, according to the state Department of Public Health.

Though risk of infection remains low for the general public, according to the CDC, California officials declared the emergency to ensure a swift and coordinated statewide response to the outbreak.

What’s the risk, and how is it spread?

Wild water birds, according to the CDC, are carriers of avian influenza A viruses. Birds infected with the disease can spread it amongst themselves and to other animals through mucous, saliva, and feces.

The outbreak poses little risk to the general public, according to the CDC. Those most likely to get infected are people working directly with infected birds and animals without personal protective equipment.

In California, people infected with the virus have experienced symptoms similar to mild cases of the flu, according to Dr. Elizabeth Hudson, Regional Chief of Infectious Diseases at Kaiser Permanente Southern California.

“For most people in the U.S who have gotten this, their symptoms have been relatively mild — cough, sore throat, fever,” Hudson said. “However, there’s a very impressive conjunctivitis or pink eye that we have seen with this, a little bit different than what we would see with seasonal flu.”

Serious symptoms of bird flu, according to the CDC, can include high fever, shortness of breath, altered consciousness, and seizures.

Though previous strains of the virus — first seen in humans in 1997 — have been deadly, this particular outbreak has been mild in comparison.

The virus has primarily affected individuals in contact with dairy cows and commercial poultry, meaning that people who do not deal with these animals are at a low risk.

No human-to-human spread of bird flu has been reported in the United States. Limited person-to-person spread — wherein the virus spreads to one or two other people, but stops there — has been reported in other countries in the past, according to the CDC.

However, a study published by scientists at Scripps Research Institute say the virus isn’t very far away from human-to-human transmission. According to the Dr. Jim Paulson, a co-senior author of the study, a single mutation of the hemagglutinin protein, represented by the “H” in H5N1, could turn the virus into a pathogen targeting human cells.

“It’s a very rare event for these mutations to be accepted into the virus population,” Dr. Paulson said. “But you only need it to happen once.”

Will cases increase?

It’s difficult to tell whether cases will continue to increase across the country and in California, according to Dr. Jim Paulson with Scripps Research Institute.

“If these inflections continue to occur, and they happen to occur in a human that’s already been infected by a human influenza virus, then a new hybrid virus could appear more easily,” Dr. Paulson. “A new influenza virus more easily adapted to human can become a pandemic.”

Though there is no approved vaccine to prevent infection, Dr. Paulson said that Tamiflu, prescribed to treat the regular flu, can also be effective in cases of bird flu and may have some preventative protection.

Why did California declare a state of emergency?

Newsom said in a statement that the declaration was made “to ensure government agencies have the resources and flexibility they need to respond quickly to this outbreak.”

The governor also said that the risk to the public remains low, but noted that the government would need to take preventative measures to help stop the spread.

The state emergency declaration allows agencies across California to coordinate testing and virus surveillance efforts, as opposed to a decentralized, regional strategy to combat the spread of bird flu.

How will this impact the agriculture industry?

While the virus is generally not fatal in cows, it causes decreased milk supply — and is always fatal in poultry.

“The impacts are primarily production and financial losses to farmers and ranchers, as the production of milk and eggs declines, and in the case of poultry, complete re-establishment of flocks is required,” Steve Lyle, a California Department of Food and Agriculture spokesman, said.

Higher prices for dairy and poultry products in stores is a direct result of the outbreak, which started in the fall, Lyle said.

The spike in infected flocks coincided with the holiday season — when demand at the grocery stores is already higher than the rest of the year.

“While most eggs consumed in California are imported from other states, about 40% are produced here, and two-thirds of egg-laying hens in California have been lost in the recent outbreak,” Lyle said. “We anticipate that supply will remain tight for at least the next several weeks.”

Dangers of consuming raw milk

There is no risk associated with consuming cooked meat or pasteurized dairy, Dr. Paulson said, but a recent recall has raised concerns about the dangers of raw milk. Raw milk and cream produced by Raw Farm, LLC in California and several products from Valley Milk Simply Bottled of Stanislaus County were recalled after the virus was detected.

Consumption of raw milk has caused severe illness and death in various mammals, especially cats, the Los Angeles County Department of Public Health announced. Five indoor cats from a single Los Angeles household died after consuming recalled raw milk products.

The department also warned against feeding animals raw pet foods. A cat from a different household in Los Angeles contracted the virus after eating two different brands of pet food containing raw poultry and beef.

How can I protect myself?

Those in contact with dairy cows, commercial poultry or backyard birds should use respiratory protections, such as masks, eye protection and gloves whenever interacting with these animals in order to lower the risk of infection. Sick animals or dead birds, whether or not confirmed to be infected, should not be handled.

People who are not regularly in contact with these animals should take precautions typically used to avoid the flu, such as hand-washing, cleaning commonly used surfaces and keeping your distance from other people experiencing symptoms.

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