Zika in the Americas (IMAGE) Florida Gulf Coast University Caption The spread of Zika in the Americas has been explosive. Since its first confirmed case in Brazil in May 2015, Zika has spread to 48 countries and territories in the Americas. It is primarily transmitted to humans by the bite of infected Aedes mosquitoes. Credit Sharon Isern Usage Restrictions For use only with news coverage of this research. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.