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.

Suspicions that there may be more bird flu going around undetected were backed by a voluntary serosurvey among veterinary practitioners who work with cattle, CDC investigators said. Out of 150 participating veterinary practitioners across the country,