Amid rising respiratory illnesses, a CDC report reveals undetected bird flu cases in US veterinarians. The spread, shown through antibody tests, indicates infections occurring beyond known zones. Experimental confirmation of H5N1 transmission through cow milk prompts officials to urge all states to join the national milk testing program.

The report is the latest evidence that the outbreak in dairy herds is spreading undetected in cows, and the spillover into people at highest risk of exposure is going unnoticed.