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Zika virus infection during pregnancy¹ has been linked to the abnormal brain development called microcephaly. Now a study finds more evidence for the connection.

Researchers at the CDC in the U.S. and the National Health Institute in Colombia found that the number of babies born with microcephaly in Colombia increased more than fourfold during a nine-and-a-half-month span in 2016 compared with the same span in 2015.

“And the peak of Zika virus outbreak in pregnant women was followed approximately six months later with a peak of microcephaly reported in the country.”

Margaret Honein, Chief of the Birth Defects Branch at the CDC and a senior author of the study. She says the finding is compelling evidence that the highest-risk period for Zika virus infection is sometime in the first half of pregnancy.

“So this both adds to the evidence and helps confirm that any country experiencing a large Zika virus outbreak should anticipate a large increase in microcephaly. This is not unique to one geographic² location, such as Brazil. What we’re seeing in Colombia is very similar to what was reported in Brazil.”

The study was in the CDC’s Mortality and Morbidity³ Weekly Report. [Esther Liliana Cuevas et al., Preliminary Report of Microcephaly Potentially Associated with Zika Virus Infection During Pregnancy — Colombia, January–November 2016]

Honein says growing evidence now exists for an association between the virus and other defects related to a damaged central nervous system.

“These include defects like club foot, joint⁴ contractures where the joints⁵ are very, very stiff, and things like congenital deafness…and eye abnormalities.”

In the U.S., the most recent cases of local transmission of Zika have occurred in parts of Florida and Texas, and there are now more than 1,000 pregnancies⁶ with laboratory evidence of Zika virus infection, plus more than 2,000 more in U.S. territories.

—Christine Herman