Zika virus (ZIKV) is a flavivirus related to the dengue, yellow fever, andWest Nile viruses and is transmitted by the Aedes mosquito species. In July 2015, 76 patients with neurologic syndromes and recent symptoms suggestive of ZIKV infection were identified in the state of Bahia, Brazil, of which 42 (55%) had confirmed Guillain-Barré syndrome (GBS).1 By July 2016, a total of 165 932 suspected cases of ZIKV infectionwere reportedtothe Brazilian MinistryofHealth,with 66 180 confirmed cases in 1850 cities and 22 of 26 states (incidence rate, 81.2 cases per 100000 inhabitants).2 It is speculated that 500000 to 1.5 million people might have been infectedwith ZIKV in Brazil since the beginning of the outbreak.3 The first cases of mosquito-transmitted ZIKV in the United States were reported in July 2016.4 Despite concomitant increases in the incidence of both GBS5 and ZIKV in Brazil, the links to neurologic complications in adults have been limited to case series on GBS,6,7 meningoencephalitis,8 transverse myelitis,9 and ophthalmologic disease.10 We aimed to prospectively evaluate adult patients with neurologic syndromes consistentwith GBS, transversemyelitis, or meningoencephalitis for molecular and serologic evidence of recent ZIKV infection. We also compared radiographic and electrophysiological findings and functional outcomes between patients positive for ZIKV infection and those negative for ZIKV infectionwhowereadmittedwith each syndrome.