How U.S. health officials are reacting to novel coronavirus

This week has seen the rapid spread of novel coronavirus both within China and internationally to at least 14 other countries. On Thursday, the World Health Organization declared it a global public health emergency. As the U.S. records its first confirmed person-to-person transmission, William Brangham talks to Dr. Anthony Fauci of NIH's National Institute of Allergy and Infectious Diseases.