Bird flu could cause the next pandemic in humans, the CDC warned, as the H5N1 strain spreading on farms continued to mutate.
In a report quietly published late last week, the agency said bird flu viruses “have pandemic potential” in a section on vaccine rollout if there is human spillover.
Also last week, a separate study from the U.S. Department of Agriculture published genetic data showing that the H5N1 strain ripping through dairy farms had acquired dozens of new mutations.
These changes could make the strain more likely to spread from cows to other animals, including humans, and make the virus resistant to antiviral drugs.
Despite this, the CDC and the World Health Organization (WHO) emphasize that the risk to the American public is low.
The map above shows the states where bird flu infections have been detected in dairy herds
This is the first photo of the Texas farm worker infected with bird flu. The infection started in the right eye and then spread to the left
The WHO said today: ‘At this time, based on available information, WHO assesses the overall public health risk from H5N1 as low.
‘(But) for people exposed to infected birds or animals or contaminated environments, the risk of infection is considered low to moderate.
‘This risk requires close monitoring and WHO and partners will continue to regularly review and publish public health risk assessments for avian influenza.’
The agency held a webinar today, which was attended by both the CDC’s own infectious disease experts and officials.
The meeting came after USDA researchers warned about the new mutations of H5N1.
They wrote: ‘Some (mutations) in the virus population were detected at a low frequency that could lead to changes in transmission (in other species) … after evolution in dairy cattle.
‘Continued transmission of H5N1 within dairy cattle increases the risk of infection and subsequent spread of the virus to the human population.’
Cattle herds on at least 36 farms in nine states have tested positive (stock photo)
In the newspaper, published as a preprint on BioRxiv that has not been reviewed by other scientists, researchers analyzed nasal and milk samples from dozens of infected cows with confirmed infections from March to April this year.
At least 491 mutations were detected in the sample, 309 of which were linked to ‘functional changes’ in the virus.
This included mutations that may make the virus more pathogenic, or more likely to cause infection, better adapted to mammals and better able to infect new species.
Testing also showed that the outbreak in cattle actually started in late 2023, about four months before it was first reported.
Researchers suggested the virus first jumped from birds to cows in the Texas Panhandle and then spread among herds in the state and to herds in Kansas, Michigan and New Mexico, among other states.
Outbreaks in several herds could not be linked to others, suggesting that the virus has not yet been detected in some infected herds.
There have also been reported cases of the virus moving from cows to wild birds, poultry, domestic cats and a raccoon.
At least 36 flocks in nine states have been infected with bird flu, data shows, although experts warn it is likely more widespread.
There are also concerns about the virus spreading among farm workers, with veterinarians saying they are hearing of many people being sick on farms but unwilling to get tested.