The U.S. Department of Agriculture (USDA) has ordered bird flu tests for dairy cattle that cross state lines, it announced on Wednesday. 

“USDA has identified spread between cows within the same herd, spread from cows to poultry, spread between dairies associated with cattle movements, and cows without clinical signs that have tested positive,” the agency said when announcing the federal order. 

The cattle need to test negative for the Influenza A virus, which encompasses the bird flu, at “approved National Animal Health Laboratory Network (NAHLN) laboratories.” If the animal tests positive, their owners will have to share information about their movement to be tracked back. 

The order from USDA comes as particles of bird flu were detected in a few pasteurized milk samples, the Food and Drug Administration (FDA) said on Tuesday. The spread of the bird flu among cattle has prompted the FDA to increase testing. 

“The novel movement of H5N1 between wild birds and dairy cows requires further testing and time to develop a critical understanding to support any future courses of action,” USDA said.

Despite the order, the agency said it has “not found changes to the virus that would make it more transmissible to humans and between people.” 

The virus has been found in eight states: Kansas, Michigan, Idaho, North Carolina, New Mexico, Ohio, Texas and South Dakota. 

At the start of April, a Texas man was infected by bird flu, but only experienced minor symptoms. The FDA advised caution when consuming raw milk and eggs, pointing to sparse information regarding the potential spread of the virus from those items.