One of Brazil’s most senior health officials has admitted that the Zika virus outbreak is much worse than originally believed, due to the fact that most patients display no symptoms. Health Minister Marcelo Castro said that Brazil will begin mandatory reporting of all cases by local government next week when most laboratories will have more up-to-date testing facilities. Yahoo News reports: On Monday, the World Health Organization declared the Zika outbreak to be a global emergency, a decision that should help fast-track international action and research priorities. In Brazil, believed to be the country hit hardest by Zika, the outbreak has sparked fear especially among pregnant women after local experts linked the virus to thousands of cases of microcephaly, or abnormally small heads and underdeveloped brains, in newborns. “Eighty percent of the people infected by Zika do not develop significant symptoms. A large number of people have the virus with no symptoms, so the situation is more serious that we can imagine,” Castro said in an interview. “Our big hope is finding a vaccine,” he added. The Zika emergency comes at a particularly bad time for President Dilma Rousseff’s unpopular government, adding a new burden to a public health system [...]