Galang RR, Avila GA, Valencia D, et al. - In the present study, the researchers sought to estimate the prevalence of microcephaly and central nervous system (CNS) defects during the Zika virus (ZIKV) epidemic in Colombia and proportion due to congenital ZIKV infection. A panel of clinical subject matter experts reviewed and classified clinical and laboratory evidence for cases of microcephaly and/or CNS defects reported under national surveillance between 2015 and 2017. Infants/fetuses with microcephaly and/or CNS defects (cases) have been classified into broad etiologic categories (teratogenic, genetic, multifactorial, and unknown). Of the 858 cases reported with sufficient information to support a diagnosis of microcephaly or CNS defects, 503 have been classified as potentially attributable to congenital ZIKV infection. Findings suggested that 58% of cases of microcephaly and/or CNS defects were potentially attributable to congenital ZIKV infection, however, evidence intensity differed considerably. This surveillance protocol could serve as a model approach for the investigation and etiological classification of complex congenital conditions.