In an abundance of caution, the CDC last week advised hospitals and labs to do faster flu testing to help identify possible bird flu cases hiding in the flock of rising flu diagnoses.

A number of bird flu cases have been reported in the Chicago area in recent weeks, leading to many questions about how quickly the virus is spreading and how worried residents should be.

H5N1 vaccines have been previously licensed, and millions are in the national stockpile. But even with the news of the ...