The U.S. Department of Agriculture is testing to confirm possible cases of bird flu in dairy cattle in California, the nation's biggest milk-producing state, USDA said on Friday.

California said on Thursday it was investigating potential cases at three dairies in the Central Valley region.

A warning sign is placed at a dairy farm in Martin, Michigan, U.S., June 6, 2024. REUTERS/Tom Polansek

The cases, if confirmed, would make California the 14th state to detect the H5N1 virus in dairy cows since March. More than 190 herds have been infected nationally, along with 13 dairy and poultry farm workers, according to federal data.

The virus's jump to cows from birds has heightened concerns that it could adapt to spread among humans. Federal officials say bird flu is a low risk for the general public and that pasteurization inactivates the virus in milk.

USDA said it is in close contact with the California Department of Food and Agriculture as part of efforts to contain the virus.