Proving Zika guilty: A long and painstaking task

By Kate Kelland LONDON,(Reuters) - Evidence is building for the theory that Zika can cause newborn brain defects and the World Health Organization is promising more answers in weeks, but nailing a definitive link will be neither simple nor swift. Picking apart numerous potential connections between mothers who show evidence of infection with the mosquito-borne virus and babies born with microcephaly, in which the head is abnormally small, will require precision and patience, specialists say. In