NEW YORK (Reuters) — A lethal H5N1 bird flu has jumped from chickens to dairy cows in at least a dozen U.S. states, raising concern that the virus may again adapt and spread. Read on to learn about the history and historical roots of H5N1, how it can spread and the measures being implemented to fight pandemics from becoming a public.
The Alarming Reach of H5N1
This strain in circulation, called H5N1, has led to the culling of millions of domestic birds and infected more than a dozen farm workers in personnel; most recently in Colorado.
TBUnlike seasonal strains of the common human H5N1, which spreads to most wild birds mainly in the more common influenza A domesticated poultry are not and waterfowl, especially ducks and geese.
H5N1 viruses, first recognized in 1959, have caused a total of four main global outbreaks including the last outbreak which began at the end of 2021. The current outbreak has already infected six continents through migratory waterfowl that directly or indirectly led to culling of millions of domestic birds and several sporadic spillover events to other mammalian species including dairy cows.
The Dairy Cow Connection
604H5N1 Outbreak in Lactating Dairy Cows a worrying development, the U.S. Department of Agriculture reported an H5N1 outbreak in lactating dairy cows from March 2024. With 192 herds across 13 states confirmed as positively H5N1, as on August 27th.
This means the virus is primarily infecting the cows mammary glands, rather than their respiratory tract–the natural home of flu viruses. This highlights the potential for mechanical transmission of virus at least in milk equipment such as milking claws that attach to cow udders.
In addition, the virus was found in raw milk, suggesting that pasteurization may not prevent H5N1 presence. Given that infected cattle move back and forth between farms, with equipment and personnel being shared across dairy operations, it is probable confirmation of transmission was documented.
Conclusion
The spread of H5N1 to dairy cows is a troubling new twist in an outbreak that has already established the virus’s ability to evolve and infect well beyond its usual species boundaries. Although the general public risk is low, bird strikes home the critical need for constant vigilance, biosecurity and continued research to understand how this highly pathogenic avian influenza may still be a threat.
