Tennessee bird flu shares
name, not genetics, of feared China strain: USDA
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[March 08, 2017] By
Tom Polansek
CHICAGO (Reuters) - The strain of bird flu that infected a chicken farm
in Tennessee in recent days shares the same name as a form of the virus
that has killed humans in China, but is genetically distinct from it,
U.S. authorities said on Tuesday.
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The U.S. Department of Agriculture identified the strain in
Tennessee as H7N9, following a full genome sequencing of samples
from the farm. It said all eight gene segments of the virus had
North American wild bird lineage.
On Sunday, the USDA confirmed the farm in Tennessee was infected
with highly pathogenic bird flu, making it the first case in a
commercial U.S. operation in more than a year.
In China, at least 112 people have died from H7N9 bird flu this
winter, Xinhua news agency said on Friday.
However, that virus has Eurasian lineage, U.S. flu experts said.
"Even though the numbers and the letters are the same, if you look
at the genetic fingerprint of that virus, it is different," said Dan
Jernigan, director of the influenza division at the National Center
for Immunization and Respiratory Diseases at U.S. Centers for
Disease Control and Prevention.
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Jernigan said the risk to humans from the virus found in Tennessee
is low. Genome sequencing shows the H7N9 virus did not have genetic
features present in the virus in China that make it easier for
humans to become infected, he said.
The virus found in Tennessee likely mutated to become highly
pathogenic from a less dangerous, low pathogenic form, he said.
Disease experts fear a deadly strain of bird flu could mutate into a
form that could be passed easily between people and become a
pandemic.
Multiple outbreaks of the virus have been reported in poultry farms
and wild flocks across Europe, Africa and Asia in the past six
months. Most involved strains that were low risks for human health,
but the sheer number of different types, and their simultaneous
presence in so many parts of the world, has increased the risk of
viruses mixing and mutating - and possibly jumping to people,
according to disease experts.
China's Center for Disease Control and Prevention has said the
majority of people infected by H7N9 in China reported exposure to
poultry, especially at live markets.
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Identifying the viruses in Tennessee and China both as H7N9 is
similar to having two cars from different states with the same
license plate number, said Carol Cardona, avian flu expert at the
University of Minnesota.
The strain in Tennessee "is NOT the same as the China H7N9 virus
that has impacted poultry and infected humans in Asia," the USDA
emphasized in a statement.
"While the subtype is the same as the China H7N9 lineage that
emerged in 2013, this is a different virus and is genetically
distinct from the China H7N9 lineage," the USDA added.
U.S. officials are working to determine how the Tennessee farm,
which was a supplier to Tyson Foods Inc, became infected. All 73,500
birds there were killed by the disease or suffocated with foam to
prevent its spread.
Tyson, the world's biggest chicken company, is "hopeful this is an
isolated incident," spokesman Worth Sparkman said.
Authorities have not identified the name of the farm or the town in
Lincoln County, Tennessee, where it is located.
(Editing by Matthew Lewis and Bernard Orr)
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