Science Focus Bird flu has been rampaging through wildlife and farm animals worldwide. Will it make the long-feared jump to people? When a highly pathogenic strain of bird flu strain of avian influenza (H5N1) began sweeping across wild birds and poultry in 2020, it already looked concerning. Five years on, the picture has grown darker and stranger than most would have imagined.
The virus has infected hundreds of millions of farm animals, spilled into mammals at an unprecedented scale, devastated wildlife, and – in the United States – established itself in dairy cattle, a species no one expected to see implicated. Human cases remain rare. But virologists say the trajectory is troubling, the data patchy and the future uncertain.
“It’s now a global problem,” says Dr Ed Hutchinson, professor of molecular and cellular virology at the University of Glasgow. “As a disease of wild animals, it’s completely out of control. It’s raging around the world, and there’s no feasible containment method other than just watching it infect huge populations of animals.”