The Atlantic The threat to humans is low. But the status quo is still pretty troubling. Of all the news about bird flu, this month has brought some of the most concerning yet. Six people working on a chicken farm in Colorado have tested positive for the virus—the biggest human outbreak detected in the U.S. The country’s tally is now up to 11 since 2022, but that’s almost certainly a significant undercount considering the lack of routine testing.
Since the current strain of bird flu, known as “highly pathogenic avian influenza H5N1,” began spreading around the world in late 2021, it has become something like a “super virus” in its spread among animals, Richard Webby, an influenza expert at St. Jude Children’s Research Hospital in Memphis, told me. Wild birds have been decimated, as have poultry farms: The virus has been detected in more than 100 million birds in 48 states. H5N1 has been around for longer than 25 years, but only recently has it regularly jumped to mammals, infecting cats, sea lions, and bears. In March, it was detected for the first time in American cattle and, since then, has already spread to 163 herds in 13 states. All of that would be worrying enough without reports of people also falling sick. Everyone who has tested positive in the U.S. has worked closely with farm animals, but each additional case makes the prospect of another human pandemic feel more real. “That’s absolutely the worst-case scenario,” Webby said. It’s a possibility, although not the likeliest one. For now, the virus seems poised to continue its current trajectory: circulating among wild birds, wreaking havoc on poultry farms, and spreading among cattle herds. That outcome wouldn’t be as catastrophic as a pandemic. But it’s still not one to look forward to.