The US Department of Agriculture will begin testing raw milk from dairy silos across the nation in an effort to better track the H5N1 bird flu that has been spreading in cattle since March. The agency announced the expanded testing of the milk supply in a new federal order Friday.

The U.S. Department of Agriculture Friday announced a new national milk testing order to check for H5N1 bird flu. It requires raw unpasteurized milk samples nationwide sent to USDA for testing.

Highly pathogenic avian influenza H5N1 was first detected in dairy cattle in March. A recent federal order by the U.S. Department of Agriculture creates a five-stage National Milk Testing Strategy, complementing an order from April. Since March, bird flu has been detected in several Michigan herds and one farmworker.