The Centers for Disease Control and Prevention (CDC) said Wednesday evening that new data suggests the mosquito-borne Zika virus is a cause of birth defects like microcephaly, a costly and life-threatening condition that is ravaging Brazil and has impacted nearly 5,000 children in the country.

“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,” CDC director Tom Frieden said in a news release. “We are working to do everything possible to protect the American public.”  

Scientists reported in the April edition of the New England Journal of Medicine that while evidence gathered doesn’t provide conclusive proof that Zika causes microcephaly and other birth defects, an increasing amount of scientifically sound research suggests that’s the case.

Since the onset of the current outbreak in April 2015, the CDC has added to its list of Zika-afflicted regions where it has advised pregnant women against traveling. Those areas include countries in the Caribbean, Central America, the Pacific Islands and South America, including Rio, the host of the 2016 Summer Olympics. In light of the possibility that Zika can be sexually transmitted, the CDC has also advised pregnant women's partners who have traveled to a Zika-afflicted region to use condoms or abstain from sex. 

Mosquito experts in the United States have expressed concern over the virus’ spread in southern U.S. states as temperatures rise heading into summer, and Washington has acted to prepare at-risk areas by reallocating Ebola funds toward preventing the spread of the Zika virus. Anne Schuchat, principal deputy director at the CDC, has said the Aedes aegypti, the primary vector of Zika, resides in 30 states. 

The CDC said in the news release that it isn’t changing its guidance on the heels of the new findings, and that determining a causal effect next would be imperative.

“This study marks a turning point in the Zika outbreak. It is now clear that the virus causes microcephaly,” Frieden said in the release. “We are also launching further studies to determine whether children who have microcephaly born to mothers infected by the Zika virus is the tip of the iceberg of what we could see in damaging effects on the brain and other developmental problems.”

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