Federal regulators on Friday stated that that they had not but found reside chicken flu virus within the first batch of retail milk samples they examined, a reassuring indication that the milk on retailer cabinets stays secure regardless of an outbreak of the virus amongst diary cows.

In an on-line replace, the Meals and Drug Administration stated an preliminary set of checks searching for reside virus, not simply genetic fragments, prompt that the pasteurization course of was successfully neutralizing the pathogen.

“These outcomes reaffirm our evaluation that the industrial milk provide is secure,” the F.D.A. wrote within the replace, including that the testing efforts have been ongoing.

Officers additionally examined toddler and toddler components, which incorporate powdered dairy, and didn’t discover the virus, the company wrote.

The F.D.A. launched into a nationwide survey of milk samples shortly after an outbreak of the chicken flu virus, known as H5N1, was found amongst dairy cows. Authorities scientists have been testing 297 samples of retail dairy merchandise from 38 states, a swath of the nation that covers areas far past the 9 states recognized to have contaminated herds.

The primary kind of testing regulators performed, a type of polymerase chain response, or PCR, is comparatively speedy, but it surely picks up solely genetic traces of the virus and doesn’t inform researchers whether or not the reside pathogen is current.

On Thursday, the F.D.A. stated that these checks confirmed that roughly one in 5 retail milk samples nationwide contained fragments of chicken flu virus, suggesting it was spreading amongst cows far more broadly than beforehand recognized.

The samples containing genetic fragments are subsequently examined for reside chicken flu virus, which, if current, may signify a widespread well being menace.

The take a look at for reside virus, known as egg inoculation, is essentially the most delicate of its type, but it surely takes time. The method entails injecting a portion of the milk product into rooster eggs, ready for the virus to develop within the egg after which searching for indicators of an an infection.

Rooster eggs are environment friendly vessels for rising flu viruses; even scarce quantities will thrive there. For that motive, the F.D.A.’s new outcomes strongly counsel that the examined samples didn’t comprise infectious virus and that pasteurization is working, scientists stated.

The unfavourable outcomes reported on Friday got here from a “restricted set of geographically focused samples,” in keeping with the F.D.A. Officers didn’t specify the place the samples had come from.

“The reply at this level appears fairly conclusive that pasteurized milk is secure,” stated Samuel Scarpino, a professor of the observe in well being sciences at Northeastern College. “The truth that it’s coming again unfavourable is basically robust proof that, at the very least within the samples they examined, there’s no reside virus.”

Uncooked milk isn’t secure to drink, consultants say, and it poses extra dangers amid the chicken flu outbreak in cattle. Nearly all milk produced on U.S. farms is pasteurized, a course of that kills pathogens with warmth. Flu viruses are recognized to be fragile and delicate to warmth.

Scientists careworn that the federal authorities would want to check extra milk samples and hold testing them because the outbreak continues. Some faulted officers for not appearing sooner.

“The F.D.A. ought to have run these checks six weeks in the past, once we first heard about it,” Dr. Scarpino stated, referring to the outbreak amongst cattle.

Dr. Scarpino additionally urged the federal government to conduct egg inoculation experiments with milk containing various concentrations of viral genetic materials. These checks, he stated, might supply reassurance that even pasteurized milk containing copious quantities of genetic fragments remained secure to drink.

Along with pasteurization, different current security procedures require that the milk of clearly symptomatic cows be stored from the industrial provide. Whereas extra research are wanted, Dr. Scarpino stated, “you begin to layer these items on prime of one another, and it turns into vanishingly unlikely there’s truly going to be an issue.”

Andrew Bowman, a veterinary epidemiologist at Ohio State College who has been finding out 150 retail milk samples he gathered across the Midwest, stated that the F.D.A. findings mirrored the outcomes from ongoing checks he was conducting for reside virus.

The evaluation from the F.D.A. on Friday confirmed that replicating virus was nonetheless unlikely to show up in retail milk samples wherever.

“I’ve received a gallon of milk in my fridge that is perhaps used tonight,” he stated.