Zika virus is a flavivirus that was first isolated in 1947 from a febrile rhesus macaque monkey in the Zika Forest of Uganda and later identified in Aedes africanus mosquitoes from the same forest (1). In 1954, the first 3 cases of human infection were reported in Nigeria (2). Serosurveillance studies in humans suggest that Zika virus is widespread throughout Africa, Asia, and Oceania (online Technical Appendix Table 1, http://wwwnc.cdc.gov/EID/article/22/7/15-1990-Techapp1.pdf). However, these studies may overestimate the virus’s true prevalence, given serologic overlap between Zika virus and related flaviviruses, such as dengue virus (DENV) and West Nile virus (WNV) (3,4).