The strain of bird flu uncovered recently on a Tennessee chicken farm is genetically distinct from a strain in China linked to a number of human deaths, Reuters reports.
The US Department of Agriculture sequenced the genome of the Tennessee flu virus to find that, though it is an H7N9 virus like the one in China, its lineage could be traced to North American wild birds. The virus in China, which the Xinhua news agency says killed 112 people this winter, has a Eurasian lineage, Reuters says.
"Even though the numbers and the letters are the same, if you look at the genetic fingerprint of that virus, it is different," Dan Jernigan from the US Centers for Disease Control and Prevention tells Reuters.
Jernigan adds that the Tennessee virus doesn't have the same genetic features that the strain in China has that make it easier for people to be infected. He suspects that the Tennessee virus mutated into a more highly pathogenic virus from a lowly pathogenic one.
Reuters adds that officials are investigated how the virus came to the farm, and notes that thousands of chickens have been culled to prevent its spread.