Very belatedly USDA will introduce a more extensive program of surveillance for H5N1 Strain B3.13 infection responsible for bovine influenza.  Molecular studies on isolates obtained from herds in Texas during March suggest that the infection was introduced in December 2023 but was only recognized as a clinical entity three months later.  USDA introduced a requirement to test herds before interstate movement of dairy animals.  APHIS considers that this precaution has limited the prevalence of the virus to 14 states with California, Idaho and Utah reporting incident cases. To date 412 herds have been diagnosed with 202 cases in California centered on the Central Valley.

Contrary to policy for poultry, USDA supports the development and deployment of an H5N1 vaccine for dairy herds with candidate vaccines currently under evaluation.

Given the small number of cases among human contacts of infected dairy herds, the Centers for Disease Control and Prevention justifiably consider that risks to the general population are minimal.  State and local agencies are encouraging the correct use of PPE to limit infections among workers. Surveillance of farm workers and their contacts is ongoing.