Genetic traces of avian influenza found in 1 in 5 milk samples nationwide

federal regulators found Fragment of avian influenza virus It was present in about 20% of retail milk samples tested in a nationally representative study, according to the Food and Drug Administration. with online update on Thursday.

The agency said samples from parts of the country known to have dairy herds infected with the virus were more likely to test positive. Regulators said there was no evidence the milk posed a risk to consumers and there was no evidence that live virus was present in store-bought milk, an assessment echoed by public health experts.

But finding traces of the virus in such a high percentage of samples taken from across the country suggests that the avian influenza outbreak in dairy cows is more widespread than official tallies of 33 infected herds across eight states. This is the most powerful sign.

“This suggests there is a lot of this virus out there,” says Richard Webby, a virologist and influenza expert at St. Jude Children's Research Hospital.

Dr Webby said he believed it was still possible to eradicate the virus, known as H5N1, from the country's dairy farms. But without knowing the extent of the spread, it will be difficult to develop effective control measures, he said.

The findings also raise questions about how the virus evades detection and where it spreads silently.some scientists criticized The federal government's testing strategy is too limited to reveal the true extent of the virus' spread.

By Wednesday, the Department of Agriculture Announcement of compulsory inspection Testing of dairy cows traveling across state lines was voluntary and focused primarily on those with obvious symptoms.

As of Wednesday, only 23 people had been tested for the virus and 44 people were being monitored after contracting the virus, the Centers for Disease Control and Prevention said.

A widespread outbreak in cattle would pose a significant risk to farm workers, the dairy industry, and broader public health. Sustained spread among cattle could give the virus more opportunity to acquire mutations, making it more transmissible between humans.

The FDA did not provide details Thursday about the number of samples or their source.

“You want to go not only to places where you know that bird flu is occurring and there are cattle, but also places where there is at least no reported bird flu,” Dr Webby said.

Experts believe that the pasteurization process, which involves briefly heating milk, should inactivate the bird flu virus, known as H5N1.

“When you destroy a virus, you release genetic material,” said Samuel Arcane, a microbiologist and food scientist at Cornell University. The genetic fragments left behind cannot cause infection.

It's “not surprising” that milk contains them, he added. “It doesn't mean milk is unsafe.”

Federal officials are still conducting the time-consuming tests needed to determine whether viable virus remains in milk after pasteurization. Scientists say that's highly unlikely.

Dr. Jeanne Marrazzo, director of the National Institute of Allergy and Infectious Diseases, said at a press conference Wednesday that some federally supported researchers have tested for live virus in retail milk, but pasteurization kills the virus. He said there were no signs that he had done so. Before milk hits grocery store shelves.

Dr Marazzo cautioned that although the results represent a small sample, the findings are “welcome news”.

“We'll have to wait and see what the FDA does to really understand the scope here,” she said.

Experts warned that finding traces of the virus in 20% of commercial milk samples does not mean 20% of the country's dairy herd is infected. “It's too early to try to do back-of-the-napkin calculations,” Dr. Arcane says.

Milk from multiple farms is usually pooled. If the virus is detected in a large number of milk samples taken from one pool, it could mean that many cows are infected, or a small number of infected cows may be shedding large amounts of virus. Dr. Arcane said that could mean that

But even in the latter case, he noted, a 20 percent positivity rate would suggest that many more herds are infected than the 33 herds.

At a press conference Wednesday, Dr. Donald A. Prater, acting director of the FDA's Center for Food Safety and Applied Nutrition, noted the novelty of this research effort. He said no studies have been completed so far on the effects of pasteurization on avian influenza viruses in milk.

Dr. Prater said regulators are examining milk at various points in the commercial supply chain, including milk on grocery store shelves, as well as dairy products, such as the difference between whole milk and cream. It added that it is also studying potential differences between the two.