Rising H5N1 bird flu cases in the U.S. prompted the CDC to study the virus in ferrets, revealing it may have the potential to spread and cause severe symptoms in other mammals.

The CDC's updated recommendations are based, in part, on the study of 115 dairy workers in Colorado and Michigan. Blood tests found eight workers had been infected with bird flu, but only four of those workers recalled having symptoms. The most common ...

The CDC recently conducted a dairy worker survey, collecting blood samples from 115 people in Michigan and Colorado who worked with cows with bird flu. Eight of those workers tested positive for the virus.