Genetic material from a particularly virulent strain of bird flu virus has been found in 1 in 5 samples of pasteurized milk, according to an April 25 update from the Food and Drug Administration. The tested milk came from a nationally representative sample and the positive results came from milk in areas with herds of dairy cows 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.
As of April 25, bird flu had been detected in 33 herds in Idaho, Kansas, Michigan, New Mexico, North Carolina, South Dakota, Ohio, and Texas. This particular virus strain has caused a devastating outbreak in wild and commercial birds since 2021. It 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) testing to inspect the milk samples. While the findings are concerning, it does not necessarily mean that the milk was contaminated with live virus–which can cause infection.
[Related: Bird flu detected in dairy cow milk samples.]
“With qPCR tests, the genetic material, not necessarily the whole active or infectious virus, is what is detected,” clinical pathologist Nam Tran said in a statement. “In the case of food, the genetic material, the RNA found in the grocery store milk samples, may not be the infectious H5N1 virus, but fragments from it.” Tram is a professor at the University of California Davis and senior director of clinical pathology at UC Davis Health.
The FDA believes that the commercial milk supply remains safe, since the testing only revealed small genetic traces of bird flu and not live virus that causes infections. The virus itself was first detected in dairy cows in the US in March and the FDA…
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