Raised Frequency of Microcephaly Related to Zika Virus Infection in Two Birth Defects Surveillance Systems in Bogotá and Cali, Colombia.

Zika virus infection during pregnancy is now known to cause congenital microcephaly and severe brain defects. In 2016, rates of microcephaly appeared to start increasing around May, peaking in July, and declining through December. The occurrence of microcephaly appears to have increased nearly 4-fold in 2 large cities in Colombia, concurrently with the reported Zika virus epidemic in the country.