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.

New CDC research suggests that a small but significant percentage of dairy farmers working near infected cows have recently contracted H5N1, often without knowing.

Federal health officials are recommending expanded testing of dairy farm workers after a new study found evidence of previously undetected cases of bird flu in humans. Why it matters: The study is leading officials to recommend the testing of all workers ...