The findings come from a new study published in Cell Stem Cell that looked at how the Zika virus interacted with human stem cells grown in a lab. The stem cells were made to mimic the types of cells that eventually form the cortex — the brain's outer layer. Within three days of being exposed to Zika, up to 90 percent of these cells had been infected. Not only did this lead to massive cell death, but the infected cells were reprogrammed to produce even more copies of the Zika virus. These experiments could eventually help doctors find new drugs to stop the virus' damage on unborn babies, the study authors argue.
The study is the first to show how Zika may be causing children to be born with abnormally small heads — a condition known as microcephaly. Researchers strongly suspect that the two conditions may be linked, due to the recent spread of both in Central and South America. Since March of last year, up to 1.5 million people in Brazil alone have been infected with the virus, according to the World Health Organization. The outbreak has coincided with a massive spike in cases of microcephaly in Brazil. Zika has also been found in the brains of developing fetuses, indicating that the virus can be transmitted from mother to child.
Today's research still does not confirm that Zika is causing these birth defects. The researchers only looked at how the virus interacts with individual brain cells in a lab setting, indicating which cells may be susceptible to the virus. To truly confirm Zika is behind microcephaly, the researchers would need to observe how Zika damages the entire brain. "Maybe the next step will be to use Zika on a 3D mini-brain to look at a more direct link," said one of the study authors Zhexing Wen, a neurobiologist at Johns Hopkins University School of Medicine. How the Zika virus is probably causing birth defects in children
The Zika virus has been linked to a life-threatening birth defect called microcephaly, though the causation has not yet been scientifically proven because the virus is so understudied. Researchers are still working on effective tests to diagnose the virus, and CDC officials have said a vaccine is likely years away.
Administration officials said the summit is intended to help spread “the latest scientific knowledge about Zika” — especially its risks on pregnant women — before it begins spreading in the U.S.
The CDC specifically hopes to “arm state and local leaders with the necessary knowledge and technical support” to come up with their own plans to fight Zika.
Three U.S. territories — Puerto Rico, the U.S. Virgin Islands and American Samoa — are already seeing the virus spread by mosquitoes. White House to hold summit on Zika virus
The work “is going to be very important,” says Madeline Lancaster, a developmental biologist who studies human brain development at the Medical Research Council Laboratory of Molecular Biology in Cambridge, U.K. The results “are quite consistent with what you’re seeing in the babies with microcephaly.”
Zika virus, named after a forest in Uganda where it was first isolated decades ago, usually causes only mild symptoms in people, including fever and rash. But after the virus started spreading across northeastern Brazil last year, doctors there noticed a striking increase in the number of babies born with microcephaly. Many of the mothers reported having symptoms consistent with Zika infection during their pregnancies. But it has been difficult to prove a link between the virus and the birth defects because blood tests for Zika virus are only accurate for about a week after infection.
Nevertheless, circumstantial evidence has accumulated. Researchers have identified the virus in amniotic fluid of pregnant women whose fetuses were diagnosed with microcephaly and also in the brain tissue of a fetus diagnosed with the disorder. But because researchers had conducted scant research on the virus before this year, they had little data to suggest how the virus could cause such damage. Zika virus kills developing brain cells