NEW YORK – The U.S. winter virus season is in full force, and by one measure is the most intense in 15 years.

Until last week, all bird flu in dairy herds had been identified as the B3.13 variant, which was believed to have come from ...

While the risk to humans of exposure from cows or milk remains low, this new flu spillover from birds into cows raises the need for continued surveillance.

Experts said it raises new questions about wider spread and the difficulty of controlling infections in animals and the people who work closely with them.