CDC confirms Zika virus does cause microcephaly
"This study marks a turning point in the Zika outbreak," CDC Director Tom Frieden said in a statement. "It is now clear that the virus causes microcephaly."
The researchers came to their conclusion by checking existing data against a set of seven rules, known as Shepard's Criteria. The list was developed by a pediatric doctor, Thomas Shepard, as a way to establish if something causes birth defects. When at least some of these criteria are met, it usually serves as "proof" that exposure to a particular agent such as a disease or some kind of chemical causes fetal abnormalities.
The data review showed that Zika met the necessary standards for being considered a defect-causing agent. First, many women who get Zika during a critical time of pregnancy such as the first or second trimester have babies with birth defects. Additionally, many of the fetuses that are exposed to Zika have followed the same, specific pattern: they are born with abnormally small heads or have other brain anomalies. And finally, many women have given birth to babies with microcephaly after having traveled to areas with ongoing Zika outbreaks. All of this evidence is enough to conclude that Zika causes microcephaly, the researchers argue, though the virus satisfies even more criteria on the list.
