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Why we still don't know exactly how bird flu is spreading between cows

Early evidence suggests that a bird flu virus called H5N1 may be infecting dairy cows through contaminated milking equipment – but poor surveillance has made it nearly impossible to rule out other possibilities

By Grace Wade

21 May 2024

New Scientist. Science news and long reads from expert journalists, covering developments in science, technology, health and the environment on the website and the magazine.

Bird flu has been spreading among dairy cows in the US

Getty Images/Cavan Images

Public health experts still don’t know how a bird flu virus has been spreading for months among dairy cows in the US – though early evidence points to contaminated milking equipment.

Since late March, 51 dairy herds across nine US states have tested positive for H5N1, a bird flu virus that has killed millions of birds and thousands of mammals worldwide. Genetic analysis of samples from infected cattle suggests the outbreak began when cows on a Texas farm contracted the virus from wild birds. It…

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