H5N1 shifting in animals
Researchers say new H5N1 mutations now let the virus infect cows’ mammary glands more easily — a biological shift that appears to explain spread among cattle but “does not appear to affect humans,” according to the University of Nebraska Medical Center. (unmc.edu) Ivory Coast has reported a highly pathogenic H5N1 outbreak at a poultry farm in Koun‑Fao that killed about 95,000 birds, widening the geographic footprint of animal infections. (reuters.com) (devdiscourse.com) Meanwhile in North America a D1.1 H5N1 variant has rapidly displaced earlier strains along migratory routes, prompting renewed pandemic‑preparedness attention. (downtoearth.org.in)
Bird flu is changing fastest in animals, not people: researchers now say some H5N1 viruses have adapted to latch onto a sugar found in cattle mammary tissue, helping explain spread in dairy herds. (unmc.edu) Influenza viruses infect cells by grabbing onto surface sugars, like a key fitting a lock. In an April 15 report, the University of Nebraska Medical Center said two mutations seen in dairy-cattle H5N1 let the virus bind NeuGc, a sugar made by cattle but not by humans or birds. (unmc.edu) The same report said that stronger binding made it easier for H5N1 to infect and grow in cow mammary tissue. The researchers said the change “does not appear to affect humans,” because people do not make that cattle-linked sugar. (unmc.edu) That animal shift is landing in a virus family already spread across birds worldwide and U.S. dairy cattle. The Centers for Disease Control and Prevention says the multistate dairy-cow outbreak was first reported on March 25, 2024, and the current public-health risk to the general public remains low. (cdc.gov 1) (cdc.gov 2) The geographic footprint is still widening in poultry. Reuters reported on April 16, citing the World Organisation for Animal Health, that Ivory Coast reported a highly pathogenic H5N1 outbreak at a farm in Koun-Fao near the Ghana border that killed 95,000 birds. (reuters.com) (woah.org) In North America, attention has shifted to a newer branch called D1.1. A Nature Medicine paper published April 15 said D1.1 spread rapidly across U.S. and Canadian migratory flyways during the 2024 fall migration and displaced earlier H5 genotypes in several flyways. (nature.com) That study linked D1.1’s expansion to detections in multiple hosts, including wild birds, mammals and 17 human cases, four of them severe or fatal. Down To Earth reported April 17 that the variant had nearly replaced earlier strains in North America by late 2024. (nature.com) (downtoearth.org.in) Scientists have been watching this virus for exactly that mix of stability and change: stable in its low assessed risk for the general public, but changing in the animals it infects and the tissues it prefers. For now, the newest evidence points to a pathogen getting better at moving through cattle and bird populations, not at spreading among people. (cdc.gov) (unmc.edu)
