H5N1 virus in latest human case has mutated, officials say
Testing of the latest human case of bird flu has revealed a “notable” mutation in the virus, officials have said.
The case, which was identified this month in a dairy worker in Michigan, marks the second human infection linked to the multi-state H5N1 outbreak among US cattle.
Genomic sequencing has now found a change in the virus compared to an earlier infection in a dairy worker in Texas, raising concerns that the virus is evolving to better infect humans.
The slight change in the virus’s genetic makeup is “associated with viral adaptation to mammalian hosts,” the Centre for Disease Control said in a statement published on Friday.
This change has also been identified as resulting in enhancement of virus replication and disease severity in mice during studies with avian influenza viruses, the agency added.
“This is exactly why I’ve been trying to call attention to deep sequencing of each virus from cows, cats, and people infected with H5N1, which is needed for a rapid and effective global response on vaccine and antiviral development,” said Dr Rick Bright, an immunologist and influenza expert, on X (formerly Twitter).
Despite the virus’s evolution, the CDC stressed the strain is still closely related to the clade of H5N1 circulating in US dairy cattle, and closely matches the two candidate vaccines currently available to manufacturers, should they be needed.
Experts think it likely that we will begin to see more human cases of H5N1 in dairy workers in the coming weeks and months, as surveillance efforts ramp-up across America.
There are currently at least 350 people under surveillance who have been exposed to bird flu-infected cattle, which have now been identified in at least 68 herds across nine states.
Last week, the US Department of Agriculture (USDA) announced a new set of measures to encourage farmers to increase their monitoring efforts, so that health authorities can better understand how the virus is spreading.
The agency will provide up to $1,500 to any farm that implements a biosecurity plan, including “enhanced” measures for people travelling between dairy farms like vets, milk haulers, and technicians – although it is unclear exactly what those measures are.
USDA has also said it will cover the cost of H5N1 testing in cattle by up to $2,000, including additional expenses for shipping fees of samples to laboratories.
Meanwhile, meat from a dairy cow sent to slaughter was found to contain particles of the H5N1 avian influenza virus last week – sparking concern over the risk of transmission via the food supply.
USDA have stressed that the US meat supply is safe, but have encouraged meat-eaters to cook beef to an internal temperature of at least 160 degrees Fahrenheit – which is classified as ‘well done’.
The WHO still considers the risk to humans low but urged countries to rapidly share information to enable real-time monitoring of the situation to ensure preparedness as the virus continues to spread.
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