The world is fighting its first epidemic of Zika. Singapore has just confirmed 15 cases of the virus locally transferred within its population taking the total number of cases in the country up to 56. The epidemic that first broke out in South America has now spread to Mexico, the rest of central America and the United States. It is suspected that south-east Asian countries like Vietnam, Philippines, Indonesia, Thailand and Singapore are seeing endemic transmission of the virus.

Zika is caused by the virus of the Flaviviridae family and spread by the Aedes mosquito. A person infected with Zika normally experiences no symptoms or only very mildness symptoms of illness. The most severe effect is on foetuses, when the virus is transmitted from a pregnant mother. Zika during pregnancy causes a serious defect called microcephaly, in which the brain is much smaller and has far fewer neurons, and other brain defects.

Researchers at the Columbia University Medical Center in New York have now discovered that in severe, genetic forms of microcephaly brain stem cells fail to divide. In a study published in Nature Communications, they explain how mutations in genes, like the NDE1 gene, inhibit the proliferation of stem cells called radial glial progenitors. These cells divide rapidly over weeks and months of normal brain development.

NDE1 defects result in failures of these cells to divide ans subsequently the production of fewer neurons and a smaller brain. Many labs investigating Zika have already suggested that the virus targets the radial glial progenitor cells so crucial to brain development.