This document summarizes information about the Zika virus. It describes how the virus was originally discovered in monkeys in Uganda in 1947 and is transmitted by Aedes mosquitos. It can also be sexually transmitted. The virus causes mild symptoms like fever and rash in most cases, but infection during pregnancy is a concern as it can cause microcephaly and other birth defects in babies. Currently there is no vaccine for Zika virus but researchers are working to develop one to protect pregnant mothers and their fetuses.