The U.S. Department of Agriculture says dairy cows that are moving between states will have to be tested for the presence of H5N1 avian flu.
In a Tuesday order, the agency said any lactating cow that is moved from one state to another will first have to register a negative test result for influenza A virus.
Officials said they would be able to perform tens of thousands of tests a day if necessary, which could help them build a better picture of how H5N1 is distributed and may spread.
The new order was issued one day after testing showed fragments of H5N1 viral material in the U.S.' milk supply. Officials reiterated at the time that the fragments pose no threat to human health, because any active viruses have been killed during the milk pasteurization process.
"While we are taking this action today, it is important to remember that thus far, we have not found changes to the virus that would make it more transmissible to humans and between people," the USDA wrote. "While cases among humans in direct contact with infected animals are possible, our partners at the U.S. Centers for Disease Control and Prevention believe that the current risk to the public remains low."
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New genetic signs of H5N1 avian flu found in US milk supply, regulators say
So far, H5N1 has been identified in dozens of dairy herds across eight states. Infections have also affected poultry flocks, wild birds and some other mammals.
Two dairy workers have been infected with H5N1 since the beginning of the outbreak, and 44 more people who have been exposed to potential bird flu infection are being monitored.
