Where did the Zika virus come from?

Zika virus was first identified in Uganda. Over the next 50 years there were occasional documented cases in other countries in Africa and Asia. In recent years, the virus has also appeared in Samoa, Cape Verde, Puerto Rico, and lots of other countries in Latin America and the Caribbean. Also in the last few years, the virus has been associated with “outbreaks"—meaning many people getting the virus in a short period of time. There have been outbreaks of Zika virus in the Federated States of Micronesia and in Brazil. As many as 1.3 million people may have the virus in Brazil alone. Many other countries in Latin America have ongoing Zika outbreaks, including the U.S. territory of Puerto Rico.