America’s national milk supply must be tested for the bird flu virus under a new federal order by the US Department of Agriculture announced on Friday.

The mandate comes at a time when authorities are seeking to grapple with the rapid spread of bird flu, known as H5N1, among dairy herds. Infections have spread to more than 500 dairy herds in California, the top state for dairy production.

More than 700 dairy herds have been reported to be infected nationwide since March, according to the USDA.

Since April, nearly 60 people have contracted the virus. According to the US Centers for Disease Control and Prevention, most of these cases are workers on infected dairy farms. So far, the symptoms have been mild and CDC officials say that the current risk to the general public from bird flu is low.

Though the potentially deadly virus is not known to spread easily among people, every infection left untreated gives opportunity for the virus to grow more contagious, researchers have warned.

Notably, scientists from the Scripps Research Institute reported that it would take just a single mutation in the current bird flu virus to produce a version able to more easily latch on to human cells.

The USDA’s new strategy to combat the virus involves testing bulk samples of raw milk from dairy processing facilities across the country.

“Among many outcomes, this will give farmers and farmworkers better confidence in the safety of their animals and ability to protect themselves, and it will put us on a path to quickly controlling and stopping the virus’ spread nationwide,” the agriculture secretary, Tom Vilsack, said on Friday in a press release.

Farmers, dairy processors and other entities handling raw milk will be required to provide samples of unpasteurized milk when requested by the government. Dairy farm owners with infected herds will also be mandated to provide details that could help officials identify more potential cases and those who came into contact with the virus.

The new rules for testing came about after many experts, including some with the World Health Organization, criticized the apparent lack of testing on both cattle and people. Previously, governmental guidance on how to deal with the outbreak was voluntary.