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Federal officials find no live bird flu virus in initial milk tests
Health

Federal officials find no live bird flu virus in initial milk tests

Federal regulators said Friday they had not yet discovered live bird flu virus in the first batch of retail milk samples they tested, a reassuring indication that milk on store shelves remains safe despite an outbreak. of the virus among dairy cows.

In an online update, the Food and Drug Administration said an initial set of tests looking for live viruses, not just genetic fragments, suggested the pasteurization process was effectively neutralizing the pathogen.

“These results reaffirm our assessment that the commercial milk supply is safe,” the FDA wrote in the update, adding that testing efforts were ongoing.

Officials also tested infant and toddler formulas, which incorporate powdered dairy, and did not find the virus, the agency wrote.

The FDA embarked on a national survey of milk samples shortly after an outbreak of the bird flu virus, called H5N1, was discovered among dairy cows. Government scientists have been analyzing 297 samples of retail dairy products from 38 states, a swath of the country that covers regions far beyond the nine states known to have infected herds.

The first type of test regulators performed, a form of polymerase chain reaction, or PCR, is relatively quick, but only detects genetic traces of the virus and does not tell researchers whether the live pathogen is present.

On Thursday, the FDA said those tests showed that about one in five retail milk samples nationwide contained fragments of the bird flu virus, suggesting it was spreading among cows much more than previously known. previously.

Samples containing genetic fragments are subsequently tested for live avian influenza virus, which, if present, could pose a widespread health threat.

The live virus test, called egg inoculation, is the most sensitive of its kind, but it takes time. The process involves injecting a portion of the dairy product into chicken eggs, waiting for the virus to grow in the egg, and then looking for signs of infection.

Chicken eggs are effective vessels for the growth of flu viruses; even scant quantities will thrive there. For that reason, the new FDA results strongly suggest that the samples tested did not contain infectious viruses and that pasteurization is working, the scientists said.

The negative results reported Friday came from a “limited set of geographically specific samples,” according to the FDA. Officials did not specify where the samples came from.

“The answer right now seems pretty conclusive: Pasteurized milk is safe,” said Samuel Scarpino, professor of practice in health sciences at Northeastern University. “The fact that it’s testing negative is really strong evidence that, at least in the samples they tested, there is no live virus.”

Raw milk is never safe to drink, experts say, and poses additional risks amid the outbreak of bird flu in livestock. Almost all milk produced on American farms is pasteurized, a process that kills pathogens with heat. Flu viruses are known to be fragile and sensitive to heat.

The scientists emphasized that the federal government would need to test more milk samples and continue testing them as the outbreak continues. Some blamed officials for not acting sooner.

“The FDA should have done these tests six weeks ago, when we first found out about it,” Dr. Scarpino said, referring to the outbreak among cattle.

Dr. Scarpino also urged the government to conduct experiments of inoculating eggs with milk containing various concentrations of viral genetic material. Such tests, he said, could provide reassurance that even pasteurized milk containing large amounts of genetic fragments is still safe to drink.

In addition to pasteurization, other existing safety procedures require that milk from cows with obvious symptoms be kept out of the commercial supply. While more studies are needed, Dr. Scarpino said, “you start putting these things on top of each other, and it becomes more and more unlikely that there really is a problem.”

Andrew Bowman, a veterinary epidemiologist at Ohio State University who has been studying 150 retail milk samples he collected in the Midwest, said the FDA’s findings reflected the results of ongoing testing it was conducting to detect live viruses.

The FDA’s analysis on Friday showed that the replicated virus was still unlikely to appear in retail milk samples anywhere.

“I have a gallon of milk in my refrigerator that I could use tonight,” he said.