Cows Have Been Infected With a Second Form of Bird Flu

If this turns out to have been something that crossed into cattle a couple months ago, a couple months is a long time not to detect it,

said Michael Worobey, an evolutionary biologist at the University of Arizona who has studied the H5N1 virus in cattle

Angela Rasmussenvirologist

Now we know why it’s really important to test and continue testing,

said Angela Rasmussen, a virus expert at the University of Saskatchewan in Canada, who helped identify the first spillover

I always thought one bird-to-cow transmission was a very rare event. Seems that may not be the case,

said Richard Webby, an influenza expert at St Jude Children’s Research Hospital

I was kind of under the belief that the bird-to-cow movement was a pretty rare event," and the fact that it has happened again is "a little bit of a 'wow' to me."

Jude Children's Research Hospital, told the New York Times on Wednesday

Angela Rasmussenvirologist

New development: this is the first detection of genotype D1.1 H5N1 virus in cattle. All cattle sequences to date were genotype B3.13 & were all descended from a single spillover. New genotype means new introduction to cows from birds."

Angela Rasmussen, a virologist, wrote on X, formerly Twitter, on Wednesday

USDA milk testing shows different strain of H5N1 #birdflu in Nevada dairy herds. Not previously detected in cows, the strain has circulated in wild birds and led to a fatal infection in a person in Louisiana last month."

Dr. Ian Weissman, a radiologist wrote on X on Wednesday

Now it looks like we have new strains of virus that may escape some of the immunity associated with the other strains of viruses that could exacerbate the epidemics among animals and wildlife,

said Gregory Gray, a University of Texas Medical Branch professor studying cattle diseases

We're seeing the H5N1 virus itself be smarter than all of us,

said Beth Thompson, South Dakota's state veterinarian

We obviously aren't doing everything we can and everything we should or the virus wouldn't be getting in,

he said

It's a vital part of national security, global security, the well-being of people, of animals and of businesses in the US,

Worobey added

We’re seeing exactly the same clinical signs,

Goicoechea said

D1.1 was initially found, I believe, in August of 2024 in the Pacific Flyway. It’s now in all four flyways, and so we know it’s in the environment, but this is the first time it’s been documented that D1.1 has been in a dairy cow,

said J.J. Goicoechea, director of the Nevada Department of Agriculture

Lots of different bulk tanks from different farms can come into one silo. And then they trace it back,

said Dr. Seema Lakdawala, a microbiologist and immunologist at Emory University who has been studying how the H5N1 virus is infecting cows

It’s much easier to control virus spread when you’re talking about a virus spreading from cow to cow than controlling spread from birds to cows,

said Dr. Scott Hensley, a microbiologist who studies the evolution of flu viruses at the University of Pennsylvania’s Perelman School of Medicine

It’s very, very similar signs to what we’ve seen for really the last year, since this started in Texas and Kansas,

he said

We didn’t get a hold on it before, and they allowed cattle to move while they were still infectious,

Hansen said

My suspicion is that cattle that had been infected with the earlier strain are not necessarily going to be protected against this strain,

Hansen added

This is not what anyone wanted to see,

Louise Moncla, an evolutionary biologist who studies avian influenza at the University of Pennsylvania, told The New York Times

This is the first detection of this virus genotype in dairy cattle (all previous detections in dairy cattle have been HPAI H5N1 clade 2.3.4.4b, genotype B3.13). Genotype D1.1 represents the predominant genotype in the North American flyways this past fall and winter and has been identified in wild birds, mammals, and spillovers into domestic poultry,

the department said