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New mutations help the H5N1 bird flu virus infect cows but not people

The mutations target a specific sugar on the surface of cows’ cells

Black and white dairy cattle graze near a wire fence in a green grass field. H5N1 bird flu viruses have evolved to better infect such cattle.

H5N1 bird flu viruses have evolved to grasp a sugar found on cattle cells, but not on humans’ or birds’. That could enable the viruses to spread more easily between cattle.

Kinga Krzeminska/Moment/Getty Images

By Tina Hesman Saey

H5N1 bird flu viruses have acquired a molecular trick that makes them more easily infect mammary glands in cattle, but this adaptation does not appear to affect humans.