Fragments of Bird Flu Virus Found in 1 in 5 Milk Samples

FRIDAY, April 26, 2024 (HealthDay News) -- Bits of bird flu virus have been discovered in roughly 20% of retail milk samples tested in a national survey, the U.S. Food and Drug Administration said Thursday.

The finding suggests that bird flu has spread far more widely among dairy cows than officials first thought.

Samples from parts of the country that have infected dairy herds were more likely to test positive, the agency noted, and regulators stressed there is no evidence yet that cow milk poses a danger to consumers or that live virus is present in milk on store shelves.

Still, 33 herds across eight states have already been confirmed to have been infected with bird flu, also known as H5N1.

“It suggests that there is a whole lot of this virus out there,” Richard Webby, a virologist and influenza expert at St. Jude Children’s Research Hospital, told the New York Times.

While it is still possible to eradicate bird flu from the nation’s dairy farms, Webby noted it is hard to control the outbreak without knowing its full scope.

To that end, the U.S. Department of Agriculture on Wednesday announced mandatory testing of dairy cows moving across state lines. Until now, testing of cows had been voluntary and focused on cows with obvious symptoms of illness.

As of Wednesday, 23 people had been tested for the virus, while 44 people were being monitored after exposure to H5N1, the Times reported. Just one human infection has been reported so far, in a dairy worker in Texas who had direct contact with sick cows. The case was mild.

Still, sustained spread among cows would give the virus more chances to become more transmissible among humans.

Experts believe pasteurization, in which milk is briefly heated, should kill the virus.

“And when you destroy the virus, it’s going to release genetic material,” Samuel Alcaine, a microbiologist and food scientist at Cornell University in New York, told the Times.

“It’s not surprising” to find them in milk, he added. “It doesn’t mean that the milk is not safe.”

Federal officials have said they are conducting tests to determine whether any live virus remains in the milk after pasteurization. Scientists have said that prospect is very unlikely, the Times reported.

Dr. Jeanne Marrazzo, director of the National Institute of Allergy and Infectious Diseases, said during a Wednesday media briefing that some researchers had tested for live virus in retail milk but didn't find any, the Times reported.

Even though the results only involved a small sample, the findings were “welcome news,” she added.

Still, “to really understand the scope here, we need to wait for the FDA efforts,” she noted.

During the briefing, Dr. Donald Prater, acting director of the FDA’s Center for Food Safety and Applied Nutrition, noted no studies have ever been done on the effects of pasteurization on bird flu virus in milk, he noted.

More information

The U.S. Centers for Disease Control and Prevention has more on bird flu.

SOURCES: U.S. Food and Drug Administration, update, April 25, 2024; New York Times