Alarm as bird flu now ‘endemic in cows’ while Trump cuts staff and funding
Experts say current US outbreak is unlikely to end without intervention with further mutation of virus likely
Melody Schreiber
Sat 22 Feb 2025 08.00 EST
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A newer variant of H5N1 bird flu has spilled over into dairy cows separately in Nevada and Arizona, prompting new theories about how the virus is spread and leading to questions about containing the ongoing outbreaks.
The news comes amid a purge of experts at federal agencies, including employees who were responding to the highly pathogenic avian influenza outbreak at the US Centers for Disease Control and Prevention (CDC) and the US Department of Agriculture.
The additional spillovers are changing experts’ view of how rare introductions to herds may be – with implications for how to prevent such spread.
“It’s endemic in cows now. There is no way this is going to get contained” on its own, said Seema Lakdawala, an influenza virologist and co-director of the Center for Transmission of Airborne Pathogens at Emory School of Medicine.
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The current outbreak is unlikely to end without intervention and needs close attention from the Trump administration to prevent the virus from wreaking more havoc.
Yet “we don’t seem to have a handle on the spread of the virus,” said Boghuma Titanji, an infectious disease physician.
Bird flu’s continued spread is happening against the backdrop of the worst flu season in 15 years, since the H1N1 swine flu pandemic in 2009-10.
The spike in seasonal flu cases puts pressure on health systems, makes it harder to detect rare variants like H5N1, and raises the risk of reassortment, where a person or animal infected with seasonal flu and bird flu could create a new, more dangerous variant.
“There’s a lot of flu going around, and so the potential for the virus to reassort right now is high,” Lakdawala said. There’s also the possibility of reassortment within animals like cows, now that there are multiple variants detected in herds, she pointed out.
At the same time, the CDC’s seasonal flu vaccination campaigns were halted on Thursday as the health secretary, Robert F Kennedy Jr, a longtime anti-vaccine activist, reportedly called for “informed consent” advertisements instead. A meeting for the independent vaccine advisers was also postponed on Thursday.
The US has also halted communication with the World Health Organization on influenza data.
The new spillovers into dairy cattle in Nevada and Arizona, detected through the new bulk milk testing strategy recently implemented in the US, are both related to the D1.1 variant of H5N1, which emerged in the fall and has come to dominate among North American birds. A teenaged girl in British Columbia suffered severe illness and a man in Louisiana died after infection with this variant.
In Nevada, a dairy worker was infected after close contact with cows, and genomic sequencing revealed a mutation that has been associated in the past with more effective spread among people.
“These are more opportunities for the virus to continue to adapt, and with adaptation, you worry that we’ll ultimately get to a point where we may have a virus that becomes capable of transmitting efficiently between humans, and that then really would change the dynamic of the outbreak,” Titanji said.
Lakdawala raised three theories for how bird flu keeps spilling over into cows.
The first would be a rare event in which fluids from a sick bird somehow came into contact with a cow’s udders – for instance, if a bird defecated into milking equipment. That was a working theory for the first spillover, detected nearly a year ago in Texas cows. But it’s rare for birds to have close contact with milking equipment, and for that to happen three times was “unlikely”, Lakdawala said.
It’s much more common for birds to perch on feeding troughs, where their feces might mix with feed. Usually, cows infected through oral or nasal contact like this don’t see the virus spread to their udders.
But it could happen in rare events – if a cow is unhealthy, for instance – that bird flu goes systemic and enters mammary tissue, where it replicates in enormous quantities, Lakdawala hypothesized.
The third theory? People could be spreading the virus from birds, or another intermediate species, to cows.
“Bird to human infections, we know happen more often,” Lakdawala said. “It’s more likely that somebody handling dead birds or chickens infected with H5 will become infected, and then it’s human to cow” transmission.
All of these theories need more evidence and research, much of which is now threatened by halts in scientific funding from the Trump administration.
Two studies temporarily halted in the CDC’s Morbidity and Mortality Weekly Report have now been released.
Blood tests on 150 veterinarians revealed three of the vets showed recent infection with H5N1. One of the infected vets worked in a state with no cases among cows, and the two others did not realize they had had contact with an H5-positive animal, indicating continued gaps in monitoring spread.
A study on two households in Michigan indicated that dairy workers may have spread H5N1 to their indoor cats.
Kevin Hassett, director of the national economic council, unveiled the Trump administration’s new strategy on CBS’s Face the Nation on Sunday in a shift away from trying to contain the outbreak.
Previously, officials “spent billions of dollars just randomly killing chickens within a perimeter where they found a sick chicken”, Hassett said. Infected poultry are culled in this manner because they are very unlikely to survive infection, and containment like this can help halt the spread to other animals – and to the people who care for them.
Hassett instead broached the idea, without providing more details, of using “biosecurity and medication” to “have a better, smarter perimeter”.
https://www.theguardian.com/us-news/2025/feb/22/bird-flu-virus-trump
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