How Zika Virus Spreads: Chain of Events Explained

Zika virus is "now spreading explosively in the Americas," World Health Organization (WHO) Director-General Dr. Margaret Chan said on Thursday (Jan. 28), and 3 million to 4 million people in the Americas could be infected by the virus this year alone, according to the latest WHO estimates. However, U.S. officials have said that the virus is likely to cause only small outbreaks in this country. To understand how the Zika virus spreads to new regions, and how researchers can tell whether a region