Is Cow Milk Safe? The Concerning Avian Influenza Breakout in Cows

Nine states in the United States have reported the presence of avian influenza virus H5N1 in cows. The flu doesn’t usually spread from cows to humans, but a worker tested positive in April. We already know that the virus replicates in the udder of cows, and milking equipment might carry and transmit the virus from one cow to another. The FDA strongly recommends that one should not drink raw milk.

The H5N1 virus has been detected in one in five pasteurized milk samples. Pasteurization is a process in which milk is heated to kill microbes and germs. It can also break down viruses and leave inactive viral remnants in the milk sample which are not seen to cause an infection. To test this, the agency performed egg inoculation tests in which a virus is incubated and grown inside an egg to see if the viral proteins, DNA or the protein coat could induce an infection. Those tests have come as negative, meaning the viral remnants found in pasteurized milk are inactive.

Viruses are very sneaky, and mutation in them can lead to the development of different variants of viruses, which may display new features. This can range from spreading to a different host to developing methods to hide from the immune system.

Currently, only one case of cow-to-human transmission of the bird flu has occurred. The patient did not develop respiratory symptoms. Instead, he had a conjunctivitis that cleared off within a few days. Human-to-human transmission has not yet been reported. Although the virus cannot spread in humans, it does appear to affect other animals including cats who drank raw milk infected with the virus and died.

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