The virus that causes the disease was first isolated in Africa in 1947. The first documented outbreak among people occurred in 2007 in the Federated States of Micronesia. An outbreak started in Brazil in 2015, and spread to the Americas, Pacific, Asia, and Africa. This led the World Health Organization to declare it a Public Health Emergency of International Concern in February 2016. The emergency was lifted in November 2016, but 84 countries still reported cases as of March 2017. The last proven case of Zika spread in the Continental United States was in 2017.