On Monday, the U.S. reported an outbreak of bird flu called H5N9 that is different from the H5N1 strain that is currently surging across the country. The outbreak occurred in a flock of commercial ducks in California, the epicenter of the bird flu crisis, according to a report from the World Organisation for Animal Health (WOAH).
"This is bad news," Dr. Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan, wrote on X, formerly known as Twitter. "It suggests reassortment of circulating H5N1 viruses with viruses containing N9 NA. Although this indicates reassortment with avian viruses, it's still bad. Reassortment makes pandemics. The last 3/4 flu pandemics (and maybe 1918 too) were reassortant viruses."
