A variant of the H5N1 bird flu is widely spread among wild birds and in several cases has caused serious illness in several humans - first emerging in cows.

The findings were conveyed in a brief update from the USDA, which traces the new variant back to the dairy cattle herd in Nevada.

This variant, known as the D1.1 genotype, belongs to the genetic lineage that has been infected with cows over the past year.

Scientists believe a spillover occurred in Texas Panhandle, Texas, at the end of 2023 to sow seeds nationwide. However, this new finding suggests that the virus jumped into at least one instance of cows.

"This shows that even if you get rid of an already established virus, you can pop up like whack-a-mole," said Michael Worobey, an evolutionary biologist at the University of Arizona.

It is unclear how long the virus has been in cattle and whether it is prevalent. For now, Worobey says it opens up a new set of questions about the trajectory of the bull outbreak and what it means for exposed humans.

One possibility: the immunity constructed in the dairy population may not bind well to this D1.1 genotype and may require readjustment of the vaccine in the pipeline. This could make it more "difficulty, complex and unlikely" to eliminate the virus from cows, Warobe said.

D1.1 cattle infection. Dr. Jürgen Richt, a veterinary microbiologist at Kansas State University, told NPR in an email. However, its trail in humanity may be a "significant change compared to the early situation".

So far, bird flu among dairy workers has largely caused mild illness. In contrast, two severe illnesses in North America were associated with this D1.1. Genotype - Among a Louisiana resident, he caught the virus from his backyard flock and died, while a teenager in British Columbia ended up in critical condition. (The root cause of her infection was never found).

Scientists have speculated that this variant may be more lethal for humans, although there may be other factors, such as the pathway to contact, which may also be one.

However, in both cases, the patient develops about mutations when he gets sick, which may indicate that the virus is evolving to better infect human cells. “We don’t know if more (people) will land in the hospital, maybe you’ll see more upper respiratory infections.”

Since much of the work in the past year has focused on other variants, Warobe said: “It takes a long time to experiment better to solve what this means for humans.

Edited by Jane Greenhalgh