The mandate targeting bulk milk transporters and dairy processors is meant to help identify herds that have caught the virus, which has spread among livestock.

A California farm expanded a recall of raw milk sold in stores and halted production after state health and agriculture officials found bird flu virus in more milk samples.

The move comes amid an outbreak of bird flu that has sickened dozens across seven states and marked the first time the virus was identified in dairy cows. Here’s what to know.