A strain of bird flu not seen in the United States since 2017 has re-emerged.
A poultry flock at an operation in Mississippi’s Noxubee County is infected with the H7N9 strain of avian influenza, the USDA’s Animal and Plant Health Inspection Service confirmed on March 12.
The Mississippi Board of Health also confirmed the H7N9 presence that date.
As a result, 47,654 chickens will be depopulated from the broiler facility.
The reappearance of H7N9 is occurring as U.S. farmers continue to try to keep the H5N1 strain at bay.
As of March 18, more than 166 million poultry have been affected by the H5N1 strain, and 989 dairy herds have been affected too.
Both strains can be worrisome for poultry producers.
The H5N1 strain can cause “almost 100% mortality in affected poultry,” but the H7N9 strand of bird flu doesn’t “cause obvious symptoms in poultry thereby increasing the difficulty of virus tracking and surveillance,” the U.S. National Library of Medicine says.