How Does Zika Damage a Baby’s Brain?

MICHAEL SMITH: When a pregnant woman gets zika virus, doctors believe it can cause a serious, often fatal birth defect called microcephaly. That means the baby's head and brain are much smaller than usual. But they haven't known how zika does its damage.

Now researchers have discovered that it targets developing brain cells. These are stem cells that give rise to the cerebral cortex, the part of the brain that controls speech, memory, movement, and intelligence. Zika doesn't kill them right away. Instead, it hijacks them and uses the cells to churn out even more of the virus so it can spread faster. And in the lab, at least, it goes after these brain stem cells much more than any other cells.

People get infected with the zika virus through a mosquito bite. It can also be spread through sex. Right now, the biggest danger is when you travel. If you're pregnant and have been to Central America, South America, or the Caribbean, let your doctor know.

For WebMD, I'm Dr. Michael Smith.