What would it take for the bird flu virus to spark a pandemic? New study has clues

Scientists have an idea of how bird flu would have to evolve in order to spread more easily among humans: a mutation in one protein on the virus' surface could help it bind better human cells. Reporter: Will Stone. Editor: Scott Hensley. SSP for ATC Thursday + digital post possibly. Spot. Embargo for study lifts at 2pm ET on Thursday.