The Centers for Disease Control and Prevention (CDC) on Wednesday confirmed that the Zika virus causes fetal defects, including microcephaly, the condition that causes infants to be born with abnormally small brains and deformed heads.
The CDC published its findings in the New England Journal of Medicine after conducting what it called a "careful review of existing evidence." The conclusion, that there is a causal relationship between the virus and the defects, puts an end to months of speculation that the two were related.
"This study marks a turning point in the Zika outbreak," said Frieden.
He added to the New York Times, "There is no longer any doubt that Zika causes microcephaly."
Freiden said the CDC was launching new studies to investigate the potential scope of Zika's impact.
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A report presented earlier this week at the conference for the American Academy of Neurology warned that the virus may cause more disorders than previously thought, including a brain swelling condition called acute disseminated encephalomyelitis, which manifests similarly to multiple sclerosis but is not permanent.
Health agencies for months have been operating under the assumption that Zika causes microcephaly, and have advised pregnant women to take safety measures against exposure to mosquitoes and avoid traveling to regions where the virus has struck. Wednesday's report also notes that no single piece of evidence confirmed the causal relationship, but that the researchers' conclusions are supported by "increasing evidence from a number of recently published studies and a careful evaluation using established scientific criteria."
The CDC said it hoped the announcement would raise awareness about the threat to those traveling to and living in affected regions in Latin America, Puerto Rico, American Samoa, and southern U.S. states like Texas and Florida where the virus is expected to be seen this year.
"Surveys have told us that a lot of people aren't concerned about Zika virus infection in the United States—they don't know a lot about it," Dr. Sonja A. Rasmussen, CDC director of public health information and dissemination, told the Times. "Now that we can be more convincing that Zika virus does cause microcephaly, we hope that people will focus on our prevention messages more closely."
As Common Dreams has previously reported, the need to further investigate Zika's impacts also highlights the urgency of addressing climate change. Justin Donahoe, a Seattle-based organizer with Environment Washington, wrote in an op-ed on Wednesday, "Unfortunately, diseases like Zika thrive in warming climates, and this is exactly the sort of epidemic that climate scientists predict will become more pronounced unless we reduce climate pollution."