Bird Flu “Has Been Shown To Persist” in This Type of Cheese, Say Virologists in New Study

We’re nearing picnic season, but a team of researchers has a warning on a food we often associate with relaxation and gatherings. While current bird flu data from the U.S. Centers of Disease Control and Prevention (CDC) suggests the overall risk to Americans remains low, news over the weekend of a cat food recall for a possible bird flu connection sparked a new wave of concern. Now, a new study suggests certain types of cheese could be at risk for bird flu contamination, too.

Published March 14, a study done by Cornell University virologists, food science researchers and dairy microbiologists spotlights “the potential public health risks of consuming raw milk cheese” in connection with H5N1 virus, also known as highly pathogenic avian influenza (HPAI)—or, simply, bird flu. The U.S. Food and Drug Administration (FDA), which helped fund the research, also published a report on the study.

Because the bird flu virus “has been shown to persist” in raw milk for at least eight weeks, the researchers examined its stability by employing a model using spiked raw milk cheese and “in commercial raw milk cheese,” specifically cheddar, “inadvertently produced with naturally contaminated raw milk.” The commercial cheese samples were submitted to the research team’s laboratory for testing.

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Though there is a federal regulation that requires cheeses made from raw milk to cure for at least 60 days to “inactivate bacterial pathogens,” the study’s results confirmed that the virus showed “remarkable stability” during the cheese-making process. However, performing sub-pasteurization of the raw milk (at temperatures 130 degrees Fahrenheit and above) “inactivated” the virus within 15 minutes, which the researchers pointed to as an alternative safety measure.

Though there have been no confirmed bird flu cases yet in the U.S. related to humans eating raw milk products, per the CDC, the study offered a word of caution: “…ingestion of contaminated raw dairy products repeatedly may increase the probability of infections.” The FDA reminds consumers that “pasteurization is effective at inactivating H5N1.”

They also suggest consumers check their cheese ingredient labels to determine if a product is made with raw milk—there is no federal mandate that suppliers include this information on labels, but “many cheeses do disclose on the ingredient list (or elsewhere on the product label) if the milk used is pasteurized or raw.”

Cheeses like brie, camembert and Roquefort, a variety of blue cheese, are generally pasteurized before they’re sold in the United States, per government regulations due to infectious disease concerns such as this.