Zika virus, a mosquito-borne flavivirus that can cause rash with fever, emerged in the Region of the Americas on Easter Island, Chile, in 2014 and in northeast Brazil in 2015 (1). In response, in May 2015, the Pan American Health Organization (PAHO), which serves as the Regional Office of the Americas for the World Health Organization (WHO), issued recommendations to enhance surveillance for Zika virus. Subsequently, Brazilian investigators reported Guillain-Barré syndrome (GBS), which had been previously recognized among some patients with Zika virus disease, and identified an association between Zika virus infection during pregnancy and congenital microcephaly (2). On February 1, 2016, WHO declared Zika virus-related microcephaly clusters and other neurologic disorders a Public Health Emergency of International Concern.* In March 2016, PAHO developed case definitions and surveillance guidance for Zika virus disease and associated complications (3). Analysis of reports submitted to PAHO by countries in the region or published in national epidemiologic bulletins revealed that Zika virus transmission had extended to 48 countries and territories in the Region of the Americas by late 2016. Reported Zika virus disease cases peaked at different times in different areas during 2016. Because of ongoing transmission and the risk for recurrence of large outbreaks, response efforts, including surveillance for Zika virus disease and its complications, and vector control and other prevention activities, need to be maintained.