Zika’s rampage last year in Brazil caused an explosion of infections and inflicted a crippling neurological defect on thousands of babies – an effect never seen in a mosquito-borne virus.
It also presented a mystery: why had a virus that had been little more than a footnote in the annals of infectious diseases taken such a devastating turn in the Americas? How had Africa and Asia, where Zika had quietly circulated for decades, escaped with no reports of major outbreaks or serious complications?
