Bird Flu Samples Found in Dairy Products Across the US


As the H5N1 bird flu virus continues to spread across dairy cattle in the US, researchers and government health officials are ramping up testing to stop the spread.

After a dairy farmer contracted the H5N1 bird flu in late March, researchers aiming to track the spread of the virus found viral RNA samples in pasteurized milk products on grocery store shelves. While further testing and contact tracing ramps up, experts are concerned about the communication necessary to alleviate the virus in dairy cattle, similar to communication issues around testing at the start of the COVID-19 pandemic.

What’s the Issue

Grocery store milk aisle cartons

Grocery store milk aisle | image credit: ColleenMichaels /

Further expanding on the recent outbreak of the H5N1 bird flu virus in dairy cattle and poultry farms, researchers have attempted to address the growing number of infections by testing dairy products around the country. After testing, they reported new discoveries about capabilities of the virus to live on beyond pasteurization.

  • In early April, the CDC released a report detailing a bird flu outbreak among cattle on American dairy farms. This led to the first positive case of bird flu in the US since April 2022. The report caused health officials nationwide to issue warnings and guidelines on how the virus can spread and how to avoid it.1 However, researchers have discovered new capabilities that have allowed the virus to live on longer than they previously predicted.
  • The most recent report of bird flu in late March led researchers to investigate dairy products in the US. Andrew Bowman, DVM, PhD, a veterinary epidemiologist at Ohio State University, took matters into his own hands and tested 150 commercial milk products across the Midwest, with the help of 1 of his graduate students. Of the 150 samples coming from dairy processing plants in 10 states, viral RNA was found in 58 samples. The US Department of Agriculture also reported that 33 herds in 8 states have tested positive for H5N1.2

READ MORE: Bird Flu Detected in US for First Time in 2 Years

Why it Matters

Despite the virus’ inability to transmit and infect humans, the fact that viral samples are reaching grocery store dairy products is extremely concerning for health officials. And with the new discovery that the virus is surviving pasteurization, researchers are worried about its increasing chances of reaching humans.

  • “The testing by PCR—polymerase chain reaction—turned up only genetic traces of the virus, not evidence that it’s alive or infectious,” wrote Megan Molteni for STAT News.2 “The FDA has been adamant that H5N1, which is heat-sensitive, is very likely killed through the process of pasteurization.” With the FDA standing on their claims that the bird flu virus is killed during pasteurization, officials are still alarmed at the fact that positive traces have been found in commercial dairy products. Bowman even purchased some contaminated milk, which he tested himself, and ended up using it with his dinner. “I’m not concerned about it at all,” he said.2 Despite viral traces of the bird flu, its inactivity after pasteurization still makes contaminated products safe to consume.
  • Although a large bird flu outbreak amongst humans is still unlikely, researchers are expressing concerns about the evolution of the virus. While its prevalence in cows is not sounding alarms from health officials, they are worried about the virus’ ability to transform into mammalian hosts and affect humans as it has more time to adapt during its spread in cows. The virus can also reach pigs, swap genes, form new mutated hybrid forms of the virus, and possibly reach humans. Although unlikely, the various possibilities within the evolution of the virus are causing officials to keep a close eye on the issue.1

Expert Commentary

  • “The fact that you can go into a supermarket and 30% to 40% of those samples test positive, that suggests there’s more of the virus around than is currently being recognized,” Richard Webby, PhD, an influenza virologist at St. Jude Children’s Research Hospital, told STAT News.2
  • “To date, we have seen nothing that would change our assessment that the commercial milk supply is safe,” the FDA said in a statement.3
  • “If we’re only testing cows with outward symptoms, we’re missing infections in those without. I have not seen evidence that makes me want to discard the fear that testing practices are absolutely shaping what we think we know about this virus. We just don’t have the right data right now to tell us what’s going on,” Jennifer Nuzzo, director of the pandemic center and professor of epidemiology at Brown University, told STAT News.2

In Depth Insights

Experts say that dairy products containing the virus are still safe to consume. However, with the recent outbreak ramping up in cows at commercial dairy farms, researchers have grown concerned about stopping the spread, raising further issues similar to the COVID-19 pandemic.

  • Sam Alcaine, MS, PhD, professor of food science at Cornell University, likened the viral traces of bird flu in dairy products to a totaled car. “A car gets in an accident. It's no longer functioning. You can't drive it. It doesn't do anything that a car does. But you sift through the rubble and you could still find the instruction manual that tells it how to work,” he told NPR.3 When it comes to the bird flu in dairy products, it is acting like the broken-down car. Although it is traceable in these products (like the car’s instruction manual), the bird flu is inactive and its ability to transmit to any other living organism is killed during pasteurization.
  • With the bird flu issue, at the time being existing mainly in dairy cattle, that’s where researchers are hoping to stop the spread. However, testing dairy cattle nationwide is quite the tall task for the CDC and other government health agencies. Since many infected cows are asymptomatic, completing mass testing initiatives is nearly impossible. Like the early stages of the COVID-19 pandemic, when testing capabilities were severely lacking, it is hard for farmers and health officials to choose which cows to test. Despite this roadblock, the CDC says it will still begin to ramp up testing—as well as exploring wastewater testing near dairy farms—to contain the spread as best as possible.2

Extra Reading

1. Health Alert Network (HAN) - 00506 | highly pathogenic avian influenza A(H5N1) virus: identification of human infection and recommendations for investigations and response. April 5, 2024.
2. Molteni M. Early tests of H5N1 prevalence in milk suggest U.S. bird flu outbreak in cows is widespread. STAT News. April 25, 2024. Accessed April 26, 2024.
3. Hernandez J. What consumers should know about the milk testing positive for bird flu. NPR. April 24, 2024. Accessed April 26, 2024.
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