No need to worry about contracting bird flu from pasteurised dairy products - MSU

FDA considers this virus to be of low risk to humans
calendar icon 27 May 2024
clock icon 3 minute read

You may have seen headlines this spring about a new problem with “bird flu” – the H5N1 avian influenza virus that has been circulating in wild and domestic bird populations since early 2022. Although the virus continues to cause headaches for the poultry sector, it’s found a new target this year – dairy cattle.

Avian influenza has been reported in several mammalian species in the past but had never been detected in cattle until earlier this year. Infected cows suffer from gastrointestinal problems, declining milk yield and can infect other cows, according to a news release from Michigan State University. This has led to some significant challenges to individual dairy farms and recently led to a testing mandate for lactating cows being shipped across state lines as well as biosecurity enhancements in dairy farms.

For most of us, the big question is whether this outbreak is a concern for human health. The Food and Drug Administration (FDA) considers this virus to be of low risk to humans. Unlike some viruses, avian influenza does appear in the milk of infected cows, and raw milk from these cows is possibly infectious. Therefore, workers in close contact with infected cattle and potentially exposed to splashes of raw milk should take preventive measures. For consumers, the situation is markedly different. Thanks to the pasteurization process that commercial dairy products undergo, there is no risk from consuming these products.

Let’s stop and consider the evidence for this. With modern laboratory techniques, it’s relatively easy to detect the genetic material from a virus (RNA in this case), even during low-grade infections. However, these techniques detect RNA whether it’s part of a viable organism or not, meaning that these results require careful interpretation. Perhaps you’ve heard about DNA that has been recovered from a woolly mammoth or the tooth pulp of ancient humans in recent years. These discoveries were the product of similar tests, which offer tremendous sensitivity to detect and decode genetic sequences but do not demonstrate that the source organism is alive.

To test whether a potentially infectious virus is present or not, an egg inoculation test is commonly used. Recently, the FDA shared the results of tests evaluating the infectious potential of pasteurized milk that had tested positive for avian influenza RNA and found no samples with viral activity. These results point to the conclusion that RNA detected in these milk samples were simply fragments of viruses that were destroyed by pasteurization.

Most of us learned in school that Louis Pasteur developed pasteurization as a method for sterilizing food products. Since that discovery in 1862, pasteurization has been widely adopted and adapted for many food applications. Yet, its importance for ensuring the safety of milk may have faded from public awareness. In an era when few of us have witnessed first-hand the scourges of typhoid fever or listeriosis, it’s easy to take for granted the technologies that made these and other food-borne illnesses relatively rare.

Should the avian influenza outbreak in dairy cattle remind us of the value of pasteurization in our food system? Absolutely. But there’s no reason to avoid dairy products and the essential nutrients they provide.

This article was published by Michigan State University Extension.

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