What We Know About Bird Flu in Dairy Cows and People

A strain of highly pathogenic avian influenza that’s been decimating wild and captive flocks of birds since 2020 is now spreading among US dairy cows — and has infected a person in Texas exposed to the sick animals. Public health officials say the overall risk to humans remains low and the patient is getting better. They aren’t recommending the destruction of the cows, which seem to recover from the infection, unlike the millions of birds that have been culled after the virus was detected among them. US officials say milk from affected cows hasn’t entered the food system, and if it did, the pasteurization process would kill pathogens such as bird flu.

The strain of avian influenza affecting the cows, H5N1, has proved to be alarmingly adept at jumping continents and species. It was first discovered in 1996 in geese bred on a farm in southern China and has since spread across the globe, rampaging through captive, commercial birds and prompting governments to order their slaughter to limit the contagion. A new variant, clade 2.3.4.4b, emerged in 2020 in Europe and appears particularly adroit at spreading among birds and the mammals that prey on or scavenge them. Outbreak numbers that typically ebb and flow have been persistently elevated in recent years.