[In Depth] A race to explain Brazil's spike in birth defects
Brazil is facing a disturbing spike in a severe birth defect called microcephaly. Babies are born with heads that are far too small, a sign that the brain failed to fully develop. Doctors there have reported nearly 3000 cases since July 2015—more than 20 times the usual rate. Scientists are scrambling to understand what is going on. The leading theory so far is that the condition is caused by a little known mosquito-borne virus called Zika that surfaced in Brazil in March and is quickly spreading through Latin America. The news has prompted the government to declare a public health emergency; some doctors are recommending women not get pregnant until more is known. Researchers are trying to develop better diagnostic tests for the virus so they can track whether mothers of affected babies were infected during their pregnancies, and other groups are hoping to use stem cell models of the...