H5N1: Mutating and blowing in the wind

According to CIDRAP, Canada Food Inspection Agency (CFIA) authors describe their discovery of a mutated H5N1 avian flu strain resistant to the antiviral drug oseltamivir (Tamiflu) on eight chicken farms in British Columbia in October 2024. “Isolates from 8 farms reveal a mutation in the neuraminidase protein (H275Y) that is exceptionally rare among clade 2.3.4.4b viruses (present in 0.045% of publicly available clade 2.3.4.4b isolates),” the researchers wrote. “NA-H275Y is a well-known marker of resistance to the neuraminidase inhibitor oseltamivir.” The USDA designated the virus as genotype D1.1. “Despite evidence to suggest this substitution reduces viral fitness, viruses harboring this substitution spread rapidly across 8 farms in the 15 days following its initial detection,” the researchers wrote. “As oseltamivir is the most widely used therapeutic and prophylactic against IAV [influenza A virus], the continued circulation of viruses harboring NA-H275Y may necessitate a re-evaluation of influenza treatment strategies in Canada.”A non–peer-reviewed study published on the preprint server bioRxiv suggests that highly pathogenic avian influenza (HPAI) virus shed in poultry droppings can be transmitted by the wind. It might not be peer-reviewed, and its difficult to prove, but as the authors point out, it’s the only explanation that fits.CDC added a few more details about the two recent human cases, including the one from Ohio and a patient from Wyoming. The Ohio patient was hospitalized with respiratory and nonrespiratory symptoms and now recovering at home. A patient from Wyoming who got sick after exposure to backyard poultry remains hospitalized after experiencing both respiratory and nonrespiratory symptoms. In terms of human scorecards: The CDC has confirmed 70 human cases, one of them fatal, since early 2024. The agency has also recorded seven probable cases.Animal scorecards: 166,012,718 US birds affected (wild aquatic birds, commercial poultry and backyard or hobbyist flocks beginning in January 2022). Infections reported in 973 diary herds across 17 states. Countless other animals—wild, in zoos, domesticated, and pets—ranging from seals and raccoons to bears and rats are affected. Many found dead or having to be euthanised. It is especially deadly to cats. Sadly I don’t have a recent count of dead cats, whether domestic kitties, cougars, bobcats, or tigers. But it’s far more than anyone would like.

It is not exaggeration to say that HPAI H5N1 is now everywhere in this country. A panzoonotic blowing in the wind, mutating as it goes…