Underreporting of Fatal Congenital Zika Syndrome, Mexico, 2016–2017

: To determine completeness of fatal congenital Zika syndrome reporting in Mexico, we examined data from the Mexican National Institute of Statistics and Geography. We found that an estimated 50% more infants died from microcephaly attributable to congenital Zika syndrome during 2016-2017 than were reported by the existing surveillance system.