USDA confirms spillover of 2nd H5N1 avian flu genotype into dairy cattle
The US Department of Agriculture (USDA) Animal and Plant
Health Inspection Service (APHIS) today announced a
new spillover of H5N1 avian flu to dairy cattle, which involves the D1.1
genotype currently circulating in wild birds and has been implicated in human
infections, including the fatal case in a Louisiana resident who had contact
with sick backyard birds.
Not even Flip's cows are safe
Until now, all dairy herd H5N1 detections have involved the
B3.13 genotype, thought to be the result of a single spillover from wild birds
in late 2023 or early 2024. The genotype has been linked to mild infections in
dairy workers, along with some poultry cullers, with conjunctivitis the main
symptom.
"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," APHIS said in
its statement.
Detection came from milk testing in Nevada
The new spillover was detected in an investigation that
followed confirmation of H5N1 in milk sampling from Nevada dairy cows. A few
days ago, APHIS reported four recent H5N1 detections in Nevada dairy herds, the
state's first since December.
Nevada officials said they were
removing large nuisance populations of European starlings to curb the spread of
the virus. The non-native species typically migrate through Nevada in the
winter and outcompete local birds and pose a risk of spreading diseases to
livestock.
APHIS said the detection doesn't change its eradication
strategy and serves as a testament to its National
Milk Testing Strategy, which, as of the middle of January, had
enrolled 36 states, covering milk from two thirds of the nation's diary herds.
H5N1 problem is here to stay
University of Minnesota epidemiologist Michael Osterholm,
PhD, MPH, said, "We shouldn't be surprised about a new spillover to
cattle, given the very significant activity in waterfowl across much of the
United States."
He added that the virus is not going away, contrary to those
who thought B3.13 would burn itself out. Osterholm is director of the Center
for Infectious Disease Research and Policy, which publishes CIDRAP News.
The USDA said it is working with Nevada agriculture
officials on the ongoing investigation to better understand the detection and
to limit further spread. It added that it will publish a technical brief on the
findings and will post the sequence on GenBank in the coming week.
