The bird flu virus hasn't yet spread from person to person, the CDC said Thursday, releasing findings from a monthslong probe into a hospitalized Missouri patient.

A second person in Missouri who wasn't exposed to either poultry or dairy cows has been infected with bird flu, U.S. health officials reported Thursday.

Centers for Disease Control and Prevention officials told reporters Thursday that there is no evidence that there has been any case of human-to-human spread of H5N1 bird flu in the mysterious situation reported last month in which several people in Missouri suffered illnesses unrelated to known animal contact.