Signs of recent bird flu infection were found in three US veterinarians, two of whom had no known prior exposure, researchers said, suggesting potentially wider spread of the dangerous virus than has been suspected.

U.S. dairy cattle tested positive for a strain of bird flu that previously had not been seen in cows, the U.S. Department of Agriculture said on Wednesday, ramping up concerns about the persistent spread of the virus.

Avian influenza (H5N1) has been spreading in the United States among dairy cows since last year. View on euronews