The United States Department of Agriculture (USDA) will dramatically increase its testing of the nation’s milk supply for bird flu under a new federal order as the agency continues to struggle to contain a bird flu outbreak in dairy cattle first confirmed in March. It requires raw unpasteurized milk samples nationwide to be collected from milk producing, dairy processing, and transport entities and shared with the USDA for testing.

The order, which officials previewed in October and announced on December 6, 2024, will require testing of raw milk samples for the H5N1 strain of the bird flu virus, from various operations that handle the milk, including dairy farms, transportation companies, and processing facilities. Six states — California, Colorado, Michigan, Mississippi, Oregon, and Pennsylvania — will be part of USDA’s first round of testing.

Highly pathogenic avian influenza H5N1 was first found in dairy cattle in the United States in March 2024. Between April 1 - October 10, 2024, 20 human cases of avian influenza A(H5) virus infection have been reported in the United States; 21 in total since 2022. Ten of these cases were associated with exposure to H5N1 bird flu-infected poultry and nine were associated with exposure to sick or infected dairy cows 12. This includes six cases in California, two of which were confirmed by CDC on Thursday, October 3, two on Wednesday, October 9, and two on Thursday, October 10. All California cases occurred in dairy workers on affected farms. All of the October California cases are from different farms except for one farm that had a case reported previously.

As of December 6, 2024, the virus has now been found in 720 dairy herds in 15 states, costing farmers significant financial losses and creating more opportunities for the virus to mutate into something that could spread from person to person.