Limited testing of raw milk for bird flu leaves safety questions unanswered

Raw milk is getting fresh scrutiny, as bird flu continues to infect dairy herds.

A highly pathogenic strain of flu, deadly to birds, has spread to at least 58 herds of dairy cattle in nine states, and to at least two people. Samples of unpasteurized milk have been found to contain the virus, according to USDA tests.

But while federal authorities have advised people not to drink raw milk, it is still on sale and easily accessible in many places across the country.

Even in Texas, where the bird flu in cows was first detected and where it has been found in more than a dozen herds, some farms selling unpasteurized raw milk to the public declined to have their supply examined, NPR found after reporters purchased raw milk and submitted it for testing on May 8.

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The USDA-approved lab authorized to test the milk for the H5N1 bird flu virus called the farms to seek their permission to examine the milk, then also declined to test the milk for bird flu when the farmers did not grant it.

“[The farms] are aware of what a nonnegative test would do to their business,” said Brandon Dominguez, the Veterinary Services Section Head at the Texas A&M Veterinary Medical Diagnostic laboratory in College Station, Texas. “They asked that we do not run the test.”

After NPR reported that the USDA had confirmed the agency does not require labs to have permission from farms to test milk samples for bird flu, Amy Swinford, the director of the Texas A&M lab, added that another reason the lab could not perform the test is that reporters did not provide the premise identification numbers for each of the farms. Those numbers are not publicly available; reporters did include the license numbers of each of the farms when they submitted samples for testing.

The lab and the farms’ refusal to test samples of raw milk comes as scientists have criticized the federal government for being slow to collect and report information about the virus. There has been no widespread testing of dairy workers to understand how many may be infected, no mandate that dairy farms test their herds if they aren’t moving cattle between states, and no clear testing data to support federal authorities’ warnings of a potential threat of bird flu in raw milk that people drink.

Advocates and critics of unpasteurized milk square off

In the void of evidence, both sides of the raw milk debate are shoring up their traditional perspectives.

Public health officials and academics say the risks are currently heightened, and that precautions should be taken until there’s a clearer understanding of the scope of bird flu in dairy cows, and how it’s spreading between animals and humans.

“Pasteurization is effective at inactivating the virus,” said Don Prater, head of the FDA’s Center for Food Safety and Applied Nutrition, in a press call on May 1. “[We] strongly advise against the consumption of raw milk – milk that has not been pasteurized – and recommend that the industry does not manufacture or sell raw milk or raw milk products made with milk from cows showing symptoms of illness, any illness, including those infected with avian influenza virus,” Prater said.

Raw milk advocates say the theoretical risks are exaggerated and are the latest chapter in their long, contentious battle with the federal government, which banned the interstate sale of raw milk in the 1980s. “The FDA will take any excuse to blast us any way they can,” says Marc McAfee, a raw milk dairy farmer in California and founder of the Raw Milk Institute, an advocacy organization.

Raw milk for sale, but not recommended

It’s not hard to get raw milk in Texas. You can pick it up at a fitness center in Austin, or drive directly to the farmhouse stoops of dozens of raw milk dairies sprinkled throughout the state. There, if you drop some money in a lockbox, you can leave with a cold gallon of milk, straight from the cow, that’s never been heated to a temperature that would kill the bacteria and microorganisms that might be living in it.

Cheryl Masraum was unconcerned about bird flu as she bought raw milk from Stryk Jersey Farm in Schulenburg, Texas, between Houston and San Antonio.

“We were keeping up on that, but it didn't seem to be a threat here,” said Masraum, noting that the outbreaks in cows were reported in northwest Texas, near the New Mexico border. “I think the raw milk is typically a much better quality, and it just tastes better.”

Masraum is part of the small but passionate group of raw milk consumers in America. Roughly 1.6% of U.S. adults frequently drink milk that’s never been pasteurized to kill germs, according to a survey from the Food and Drug Administration.

Now, the bird flu outbreak in dairy cattle has prompted federal health officials to renew their warnings to the public not to drink raw milk.

Public health officials say they’ve long recommended against drinking raw milk, because it can harbor disease-causing bacteria. Pasteurization, the brief heating of milk, can kill or inactivate microbes.

Still, the risk of contracting bird flu from raw milk is largely theoretical. “There's not a tremendous amount of studies showing the infectivity related to this virus and raw milk products,” FDA’s Prater said during the press briefing.

How much bird flu virus is in milk?

The FDA found bird flu virus fragments in 20 percent of pasteurized, grocery store samples the agency collected and tested, according to a recent survey. Those virus fragments were not capable of causing infection, according to FDA tests.

According to the federal government, the virus appears to be spreading between herds through the movement of infected cows. In the current working theory, H5N1 jumped from birds to dairy cows in Texas towards the tail end of 2023. Then, “the transportation of cattle from Texas to a number of other states basically created problems in those states,” U.S. Secretary of Agriculture Tom Vilsack told reporters May 10. Vilsack said that the USDA’s current strategy – of requiring cows to test negative before they move across state lines – is aimed at “trying to contain the spread and eventually allowing for specific herds to have the virus peter out.”

Raw milk advocates say their farms are small, and their herds are relatively isolated. Raw milk can only be legally purchased in the state it’s produced in. “There’s been no exposure of our cows with cows that are positive from other states. We don’t buy cows from other states. So why would [our cows] be positive?” McAfee, in California, says. No cows or milk samples from California have tested positive.

Virus researchers counter that there’s not enough ongoing surveillance to establish the limits of the outbreak. “I don't know that we have the information because we haven't been systematically testing,” saysDr. Helen Chu, an infectious diseases specialist at University of Washington in Seattle. “This is a virus that mutates very quickly, that goes from humans to birds to pigs to cows – to all of these different species.” Given that avian influenza is carried by wild waterfowl and migratory birds “who are flying all over the place and defecating into the feed of farms everywhere… I don't know that we've been looking [enough] to know for sure that this is the one event,” Chu says.

One way to determine if there’s H5N1 virus in raw milk, intended for humans to drink, is to test for it. Chu’s colleague Lea Starita, who leads a genomic testing lab at the University of Washington, has tested dozens of milk samples, raw and pasteurized, purchased from local farmer’s markets and grocery stores. She has found probable viral fragments in about 5% of the samples, though the raw milk samples have tested negative.

But testing raw milk for bird flu is not happening regularly, and farms have declined requests to have their raw milk tested, NPR and others have found.

“They're frankly afraid of what's going to happen to their farms, their families. It isn't just strictly a public health issue. It's an issue of economics and frankly, survival,” said Swinford, the director of the Texas A&M lab that declined to test the milk NPR submitted for analysis.

On May 21, an employee of the Texas A&M lab confirmed that the lab could ship the samples to another laboratory for NPR, and that shipping was a service the lab provided to clients. But on May 22, Swinford called a reporter to say that she would not allow that for the raw milk that NPR purchased and submitted for testing of bird flu.

“I’m not going to facilitate that…because these dairies told us not to test them,” Swinford said.

Could consuming avian influenza in raw milk infect people?

The federal government’s warnings against raw milk consumption are based on known dangers. Raw milk has been implicated in food poisoning of more than 2,500 people food poisoning over the past 20 years, with bacteria such as Campylobacter and Cryptosporidium. But whether unpasteurized milk can give people bird flu is unclear.

Farm cats that drank unpasteurized milk from infected cows became seriously ill – some cats went blind, experienced serious neurological effects and died after drinking it, according to a recent report in the journal Emerging Infectious Diseases. And mice that were fed samples of infected, unpasteurized milk from cows in New Mexico got sick very quickly and had high virus loads in their respiratory tracts, according to a May 24 report in the New England Journal of Medicine, co-authored by Swinford at Texas A&M.

So far, there are no confirmed cases of humans getting bird flu from drinking raw milk. Two dairy workers – one in Texas and one in Michigan – got sick with avian influenza after working closely with infected cows. In both cases, the workers developed eye infections and have since recovered.

On May 1, the CDC said health authorities had monitored over 100 exposed workers without finding any bird flu infections. But a veterinarian in Texas told the publication Bovine Veterinarian of sick farm workers that have not been tested.

As far as consumers go, McAfee and other raw milk advocates see the lack of cases to be reassuring. If nobody has caught bird flu from drinking raw milk yet, it may not happen at all.

But public health officials maintain that bird flu in dairy cattle remains a new, evolving situation. “There are a lot of unanswered questions, and much more to learn,” says Lori Freeman, head of the National Association of County and City Health Officials. “Until we learn more about this particular pathogen spreading among animals and to people, we should be taking an abundance of precaution.”

Raw milk farmers say they’re following the developments closely, and working to ensure that their cows are healthy and their milk is safe. And that these arguments are unlikely to sway many of their committed customers. “People that follow us – if FDA says it's bad, they'll run [towards] it,” McAfee says, “In my opinion, here in California with our raw milk, it's much ado about zero.”