It's the mother of deadly bird flu. A little-known chicken virus found across Eurasia has spawned another killer offspring - H10N8 -which has killed one person and made another critically ill in China. Crucially, H10N8 shares an ancestor with the other bird flus infecting people in the region, H5N1 and H7N9, deepening concerns that the ancestor virus could produce more killers. The common ancestor is a virus called H9N2. "H9N2 is the enabler, the one to worry about," Robert Webster of St Jude Children's Research Hospital in Memphis, Tennessee, told New Scientist. Bird flu usually infects the gut of ducks, but H9N2 has evolved into a benign respiratory virus in chickens, spreading across Eurasia. When multiple flu viruses infect the same host, they can swap genes. H5N1, H7N9 and H10N8 all got some or all of their "internal" genes from H9N2 -those for the enzymes that replicate the viral genome, for example, as opposed to those that code for surface proteins.
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