CDC warns of expanding Zika threat in U.S.

The Centers for Disease Control and Prevention warns that the Zika virus in the U.S. could spread much farther north than previously thought. The CDC originally focused on the Southeast when it looked at the location of mosquitoes that carry the virus. But new guidance shows the two species have a far greater range that could stretch to big cities like New York and San Francisco. CBS News medical contributor Dr. David Agus joins "CBS This Morning" from Los Angeles to discuss the threat.