Infectious bird flu can remain in refrigerated raw milk for 5 days

Raw milk may be more dangerous than assumed. Researchers have just found evidence that influenza viruses that end up in raw milk can infect people for up to about a week.

Scientists at Stanford University conducted the study aimed at determining the risk of exposure to influenza through contaminated milk. They found that a certain strain of influenza A virus was still infectious after five days in refrigerated raw milk. The results suggest that raw milk is an effective transmission route for similar influenza strains, especially avian influenza viruses that are now actively spreading among dairy cows.

Pasteurization is the simple, brief heating process of foods and liquids to kill microbes that can cause spoilage or food poisoning. Not surprisingly, extensive research shows that unpasteurized or raw dairy products can spread harmful germs. A 2018 study, for example, Found Raw milk and cheese products account for 96% of all reported foodborne illnesses attributed to dairy products over a five-year period.

The emergence of H5N1, a strain of the highly pathogenic avian influenza A (HPAI) virus, in dairy cows this year has made raw milk even more of a gamble. People have already detected the H5N1 virus in commercially sold raw dairy products. Some animals, especially cats living on farms, are suspected of becoming infected with the H5N1 virus by drinking raw milk. But the Stanford researchers say theirs is the first to examine the persistence of influenza in raw milk under conditions more realistic for people.

The researchers cultured raw milk samples with the H1N1 strain of influenza A. They used an initial dose of the virus similar to the doses seen in contaminated brand-name milk products (although thanks to pasteurization, no Contagious virus found in these products). They then kept the samples refrigerated at a typical temperature and tracked how long it took for levels of viable virus to drop before it was no longer able to infect someone. They also tested the effect of pasteurization on the virus’s ability to survive.

As is the case with Other researchThey found that pasteurization completely eliminated the presence of any infectious influenza virus. But it took up to five days for raw milk samples to no longer become infectious.

“Overall, our study demonstrates that influenza viruses remain infectious in raw milk, where they can pose a significant risk to human health,” the researchers wrote in their paper. published This month in the magazine Environmental science and technology letters.

The study looked at a different strain of influenza A than the H5N1 strain. But other studies have shown that Infection of both strains They appear to degrade at about the same rate in milk, and influenza A viruses are generally not very different from each other in this respect. So H1N1 is potentially a good alternative to H5N1.

As of Early DecemberH5N1 outbreaks among dairy cows have occurred in 16 states this year, although only California and Nevada reported cases last month. In the United States, 60 human cases of H5N1 have been documented, most of them linked to contact with infected cattle or poultry.

So far, human cases have generally been mild, and the virus is not thought to have adapted to spread easily between people yet.

But there have been more serious cases of H5N1 I mentioned also. The longer these strains are allowed to spread among cows and other mammals like us, the greater the risk that a nightmare version of the H5N1 virus will emerge and unleash a widespread epidemic — a risk that is only amplified by the continuing popularity of raw milk. About 4% of Americans do Thought to be consumed Raw dairy products at least once a year, with 1% consuming them regularly.

“This work highlights the potential risks of avian influenza transmission through raw milk consumption and the importance of pasteurizing milk,” said Alexandria Baum, lead researcher on the study. statement From the university.

Unfortunately, the same people who love raw milk products are also likely to ignore any warning about them. Its raw milk sales It just went up Since the emergence of the H5N1 virus this year, even in the face of Remember linked to bird flu. Many followers of raw milk continue to spread misinformation about its supposed benefits compared to pasteurized milk, such as boosting people’s immunity.