A disease linked to the Zika virus in Latin America poses a global public health emergency requiring a united response, the world health organization has said. Experts are worried that the virus is spreading far and fast, with devastating consequences. The infection has been linked to cases of microcephaly, in which babies are born with underdeveloped brains. There have been around 4,000 reported cases of microcephaly in Brazil alone since October. The W.H.O alert puts Zika in the same category of concern as Ebola. Who director general, Margaret Chan called Zika an "extraordinary event" that needed a coordinated response.