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,

A new Centers for Disease Control and Prevention study suggests that bird flu may be spreading under the radar in the U.S. In September, the CDC tested 150 veterinarians who primarily worked with cattle in the past three months.

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.