CDC, Brazil start big study to test Zika link to birth defects

U.S. and Brazilian researchers are heading to João Pessoa in the state of Paraíba on Monday to recruit mothers and babies in one of the biggest government-led studies to understand whether the Zika virus is linked to microcephaly, a rare birth defect. Brazil has confirmed more than 500 cases of microcephaly, defined by an unusually small head, since the start of the outbreak. The spike in microcephaly prompted the World Health Organization on Feb. 1 to declare Zika an international health emergency.