A baby with microcephaly in Brazil goes to physical therapy.

A baby with microcephaly in Brazil goes to physical therapy. Andre Penner / AP

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CDC: There's No Doubt the Zika Virus Causes Microcephaly

New finding does not change the CDC's existing recommendations to pregnant women.

The Zika virus definitively causes brain damage and microcephaly, a congenital birth defect in which infants are born with abnormally small heads and brains, according to the US Centers for Disease Control.

“It is now clear that the virus causes microcephaly,” director Tom Frieden said in a statement. “We’ve now confirmed what mounting evidence has suggested, affirming our early guidance to pregnant women and their partners to take steps to avoid Zika infection and to health care professionals who are talking to patients every day.”

The CDC conducted a study published Wednesday (April 13) in the New England Journal of Medicine that reviewed all the existing evidence linking Zika to microcephaly. Since May 2015, the rapidly rising cases of Zika in Brazil and other tropical countries have been linked to the rising number of babies born with microcephaly. There is no new evidence that shows the direct causality between the two, but the CDC concluded that existing data meet the burden of proof.

The new finding does not change the CDC’s existing recommendations to pregnant women, who are advised to avoid traveling to countries where Zika is abundant. If they live in one of these areas, they should consult their doctors about ways to avoid mosquito bites—Zika’s primary mode of transmission.