After months of speculation and accumulating data, the Centers for Disease Control and Prevention officially confirmed Wednesday that the Zika virus does indeed cause microcephaly, a devastating birth defect in which babies are born with small, misshapen heads and brains.
Researchers at the agency came to the conclusion after reviewing existing data on the virus. No piece of evidence was decisive, the authors note. On the contrary, the accumulation of data from numerous sources convinced them of the link. Their analysis has been published in the New England Journal of Medicine.
“This study marks a turning point in the Zika outbreak,” Tom Frieden, director of the CDC, said in a statement. “We are also starting further studies to determine whether children with microcephaly born to mothers infected with the Zika virus represent the tip of the iceberg of what we might see in harmful effects on the brain and other developmental problems.”
Zika, currently sweeping through South and Central America and about to enter the US, generally causes only mild illness in adults. But in pregnant women, the virus has been linked to causing not only microcephaly, but also miscarriages, premature birth, vision problems in babies, and other birth defects. “We have learned that the virus is associated with a broader set of complications during pregnancy,” Anne Schuchat, CDC chief deputy director, told reporters Monday at a briefing at the White House. “We keep learning pretty much every day,” she said, “and most of what we learn isn’t reassuring.”
That’s according to a study published Monday by the journal Science discovered that the Zika virus preferentially kills developing brain cells. When researchers released the virus onto neural stem cell balls, which are a model for embryonic brain development, Zika destroyed them within days. In another experiment, the researchers grew brain organoids — another bundle of brain cells used to model brain development, these with more structures that resemble real brains — and then infected them with Zika. The virus killed 40 percent of the cells of the organoids.
The findings reflect other study results and what researchers have seen in fetuses. In a study published last month, researchers reported seeing the virus melt in the brain of a baby in the womb after the mother was infected.
In addition to pregnancy complications, the virus is also associated with rare cases of a crippling autoimmune disease, Guillain-Barré syndrome. This week, researchers reported preliminary data that the virus may also cause another autoimmune disease called acute disseminated encephalomyelitis, which is similar to multiple sclerosis.