East Texas health officials say it's "just a matter of time" before Zika hits ETX

This could help explain the reported increase of microcephaly in Brazil-a rare disorder that causes infants to be born with abnormally small heads and underdeveloped brains.

The new work provides experimental evidence that once the virus reaches the developing brain, it can infect and harm cells that are key for further brain development, said Hengli Tang of Florida State University, a lead author of the work.

Zika virus has grabbed national headlines this year and is known to affect countries in the Caribbean as well as Central and South America.

On February 1, the World Health Organization declared the spread of the Zika virus to be an global public health emergency.

While the exact workings of Zika remain a mystery, some case reports have indicated that parts of the developing brain progress normally after infection, but that the cortical structures are missing. Contra Costa County has reported two cases, with San Francisco and Napa counties reporting one each. Brazil said it has confirmed more than 640 cases of microcephaly and considers most to be related to Zika infections in the mothers. Zika infects adults when mosquitoes deposit the virus on human skin, and our immune cells carry it into the blood.

State public health officials have confirmed six cases in the state, and update those numbers each Friday. But despite anecdotal evidence, there has been very little evidence to support the link.

Florida State already had the virus stored in its lab, Tang said.

Six of the infected patients are still having symptoms, according to the Florida Department of Health. Then he realized how well-equipped his lab was to study it.

The WHO official said several factors pointed to the Games being broadly safe from Zika, including Brazil's effective response to the outbreak and winter conditions in Rio in August, which should limit the mosquito population. The mosquito-borne virus infects a kind of neural stem cell that goes on to form the cerebral cortex, the brain's outer layer responsible for intellectual capabilities and higher mental functions, the study showed. The results were published today in the journal Cell Stem Cell.

They got started immediately. Researchers could add different compounds to the stem cells when they are exposed to Zika, to see which drugs work best at preventing infection or cell death. Cortical neural progenitor cells in turn give rise to immature neurons.

Something else became clear, too.

Separate laboratory research strengthens that case by showing the virus targets fetal brain cells.

As predicted, Zika virus attacked the human neural progenitor cells.

The goal was to find or disprove any link, Tang said. "The cells are precious".

When they were finished, they sent the infected brain cells to Emory University in Atlanta, where scientists determined the cells' genes had changed.

"In addition, it will slow down the growth, potentially providing a link to neurological defects, such as micocephaly", Tang said. "This research is the very first step in that, but it's answering a critical question".

"Now that we know cortical neural progenitor cells are the vulnerable cells", Song says, "they can likely also be used to quickly screen potential new therapies for effectiveness".