Last year, in Brazil and Columbia, the number of Zika cases began to spike and on February 1, the World Health Organization declared an international health emergency.
The very next day, the very first Zika case was reported in the United States. Doctors said the virus was transmitted not by mosquito bite, but by sex. Today, Dave Marash speaks with Seema Yasmin of the Dallas Morning News about how and how quickly the virus spreads.