Genetic material from a particularly virulent bird flu virus strain has been found in 1 in 5 samples of pasteurized milk. April 25 update from the Food and Drug Administration. The milk tested came from a nationally representative sample and the positive results came from milk in areas with dairy cow herds where highly pathogenic avian influenza (HPAI) or H5N1 infections have been detected. The FDA's new test results indicate that the virus has spread further among dairy cows than previously indicated.
From April 25 there was bird flu detected in 33 herds in Idaho, Kansas, Michigan, New Mexico, North Carolina, South Dakota, Ohio and Texas. This particular strain of the virus has caused a devastating outbreak wild and commercial birds since 2021. The disease first spread to mammals in 2022 and can occasionally infect humans. Only two human cases of HPAI have been reported in the United States, according to the Centers for Disease Control (CDC).
The FDA used quantitative polymerase chain reaction (qPCR) assays to inspect the milk samples. While the findings are concerning, it does not necessarily mean the milk was contaminated with a live virus, which can cause an infection.
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“QPCR testing detects the genetic material, and not necessarily the entire active or infectious virus,” says clinical pathologist Nam Tran. said in a statement. “In the case of food, the genetic material, the RNA found in supermarket milk samples, may not be the infectious H5N1 virus, but fragments of it.” Tram is a professor at the University of California Davis and senior director of clinical pathology at UC Davis Health.
The FDA believes the commercial milk supply remains safe because the tests revealed only small genetic traces of bird flu and no live virus that causes infections. The virus itself was first discovered in dairy cows in the US in March, and the FDA announced on April 23 that it had found virus fragments in commercially sold milk.
Milk sold in supermarkets is pasteurized. This process kills harmful bacteria and viruses by heating milk at a certain temperature for a certain period of time. The virus particles detected by highly sensitive qPCR tests were likely the remains of viruses that had already been killed during the pasteurization process.
The FDA will take action to determine whether an active, infectious virus remains in the milk samples egg inoculation tests. These residues are often considered the “gold standard” for determining the viability of a virus. In these tests, scientists inject the virus sample into a raw chicken egg to see if it replicates or not. This test produces the most sensitive results, but takes longer than other methods.
“Virus isolation spreads viruses and requires a live virus particle to begin with,” Beate Crossley, professor of clinical diagnostic virology at the UC Davis School of Veterinary Medicine said in a statement. “A positive virus isolation result from a sample would indicate that there is live, infectious virus present in the sample.”
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The World Health Organization has done the same urged public health officials to prepare for a possible spillover to humans in the future. While cases of people get infected and seriously ill from bird flu are rareThe more it spreads among mammals, the easier it will be for the virus to develop and spread.
Health officials continue to believe that commercial milk is unlikely to contribute to the spread of the virus to humans and that pasteurization is the best line of defense. Consuming raw or unpasteurized milk is dangerous, no matter what the internet says. Raw milk has no additional nutritional benefits and it may be contaminated with harmful germs. In fact, the CDC considers raw milk to be one of the riskiest foods a person can consume.
As an evolving situation, the USDA And FDA will continue to share updates.
