Bird flu is spreading. Are supermarket eggs and milk safe?

In early December, Sonoma County, California, declared an agricultural disaster when two poultry farms had to kill their entire flocks to try to stop “highly pathogenic avian influenza” — or bird flu — from spreading. This particular strain of bird flu, H5N1, had first been reported in the United States in early 2022 when escalating avian horror stories began popping up in headlines: Two zoos reported bird flu among their flocks, prompting zoos across the country to pull their birds off-display; three bald eagles were infected in Georgia and died; hundreds of infected birds were found dead at a lake in the Chicago suburbs.

Tens of millions of turkey and chickens at commercial farms have since been killed to try to suppress the outbreak.

During a time of already sustained inflation, as avian influenza cases rose, so did the cost of eggs. As reported by the University of Arkansas System Division of Agriculture, bird flu was blamed for higher egg prices in 2023, which peaked at $4.82 per dozen in January (last month, they hovered around $2.99 per dozen, for reference).

Then, late Thursday, the Food and Drug Administration announced that one in five commercial milk samples tested in a nationwide survey contained particles of the H5N1 virus, a discovery that has led some experts to voice concern that “the virus is more widespread among dairies than we had previously thought,” as reported by Reuters.

But how concerned should home cooks be about the impact of bird flu on the safety of their egg and dairy products? Let’s dive into what we know.

What is bird flu? 

According to the Centers for Disease Control and Prevention (CDC), avian influenza, or bird flu, is a virus naturally spread among wild aquatic birds worldwide. The disease was first identified in Italy in the late 19th century and was initially referred to as “fowl plague,” as it was confused with a form of fowl cholera. The term “bird flu” gained more popularity through the 20th and 21st century, following outbreaks of highly pathogenic strains such as H5N1 and H7N9 (and the first  International Symposium on Avian Influenza held in Paris, France, in 1981).

The CDC maintains that bird flu viruses do not normally infect humans, however, in a current situation summary, the organization says that, “sporadic human infections with bird flu viruses have occurred.” Such is the case with the current strain, H5N1.

On April 1, a Texas dairy farm worker who had been exposed to cattle tested positive for H5N1 bird flu. According to a release from the CDC, “the patient reported eye redness — consistent with conjunctivitis — as their only symptom, and is recovering.”

“The patient was told to isolate and is being treated with an antiviral drug for flu,” they write. “This infection does not change the H5N1 bird flu human health risk assessment for the U.S. general public, which CDC considers to be low.”

This is the second human in the United States to have reported being infected under the current wave of the disease; the first was a 2022 case in Colorado involving a “person who had direct exposure to poultry and was involved in the culling (depopulating) of  poultry with presumptive H5N1 bird flu.”

While the transmission of bird flu to other mammals is rare, it is possible. Currently, nine states — North Carolina, Ohio, Michigan, Texas, New Mexico, Colorado, Kansas, South Dakota and Idaho — have reported outbreaks of bird flu among cattle, with an estimated 34 herds being impacted as of Friday. There are several ways the cows could have become infected, including coming into direct contact with infected birds, living in a contaminated environment, or consuming feed containing contaminated poultry by-products or droppings.

Are supermarket eggs and milk safe to consume? 

On Tuesday, the Food and Drug Administration said that samples of pasteurized milk had tested positive for remnants of the bird flu. At the time, they stressed that the materials were inactivated and that they “do not represent actual virus that may be a risk to consumers.”

According to Dr. Scott Roberts, a Yale New Haven Hospital Infectious Disease specialist and assistant professor in infectious diseases at Yale School of Medicine, there’s little risk of transmission in supermarket eggs and milk because one needs to have direct contact with the infected animal.

“But more than that, the pasteurization process would kill any viable virus in there,” Roberts said.

The FDA issued a statement communicating a similar message on Friday after the agency had received additional results from “an initial limited set of geographically targeted samples as part of its national commercial milk sampling study underway in coordination with USDA.”

“The FDA continues to analyze this information; however, preliminary results of egg inoculation tests on quantitative polymerase chain reaction (qPCR)-positive retail milk samples show that pasteurization is effective in inactivating HPAI [avian influenza],” they wrote. “This additional testing did not detect any live, infectious virus. These results reaffirm our assessment that the commercial milk supply is safe.”

As a result, experts recommend avoiding unpasteurized or raw milk and egg products.

What’s next? 

Until now, farmers only had to test their dairy cows for bird flu voluntarily or if their herd showed symptoms of infection, but the USDA announced last week that every lactating cow must now be tested and post a negative result before moving to a new state. This will help officials track the disease and understand how it is spreading, according to Michael Watson, an administrator with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service.

“We believe we can do tens of thousands of tests a day,” Watson told the Associated Press.

Then, according to the FDA’s Friday statement, the agency will continue further assessing retail samples from its study of 297 samples of retail dairy products from 38 states.

“All samples with a PCR positive result are going through egg inoculation tests, a gold-standard for determining if infectious virus is present,” they wrote. “These important efforts are ongoing, and we are committed to sharing additional testing results as soon as possible. Subsequent results will help us to further review our assessment that pasteurization is effective against this virus and the commercial milk supply is safe.”