While this study does not prove the direct link between Zika and microcephaly, it does pinpoint where the virus may be doing the most damage. Dr Guo-li Ming, a professor of neurology, neuroscience, psychiatry and behavioral science at Johns Hopkins University in Baltimore, said: "Studies of foetuses and babies with the telltale small brains and heads of microcephaly in Zika-affected areas have found abnormalities in the cortex, and Zika has been found in the foetal tissue".
Scientists from Johns Hopkins University, Emory University and Florida State University found that the virus likely targets a type of cell that actively divides in the human brain between the second and fourth month of gestation.
The news was made public after Napa County health officials had reported a pregnant woman testing positive for Zika.
That caused researchers to scramble and find a link between the virus and microcephaly in babies-a neurological condition that causes abnormally small heads and developmental delays. Since then, two U.S.-Brazilian studies have sought to confirm that the virus is responsible for the birth defect, and that it can also cause Guillain-Barré syndrome - a temporary paralysis - in adults.
"We're starting to build the case epidemiologically that maternal infection with this virus is linked to poor fetal outcomes", added Dr. Sallie Permar, a specialist in maternal-fetal infections at the Duke Human Vaccine Institute.
Researchers did not take the brain cells from embryos; they created them from stem cells obtained from other sources. The department is providing area doctors, including obstetricians, up-to-date information about the virus, including questions to ask patients who may be exposed to Zika and common symptoms, said spokeswoman Lisa de Hernandez.
Researchers also found that infected cells pump out more virus.
There's no evidence that the cells are employing antiviral responses, which means we don't know whether or how the virus is being cleared from the precursor cells, said Ming, a neuroscientist interested in brain disorders like microcephaly.
Like other viruses, Zika hijacks cellular machinery to make copies of itself and eventually destroys infected host cells.
Indonesia, Thailand, Cambodia and the Philippines have reported or indication of autochthonous Zikavirus transmission in Asia.