How Zika became a threat

摘要

Don't get pregnant, at least for now. That is the chilling advice from governments battling the Zika pandemic, as evidence mounts that the mosquito-borne virus can cause severe birth defects. As the scale of the impact starts to emerge, scientists are scrambling to learn more about the little-known virus. Is it evolving to be more severe and contagious in humans? Or has it taken off so aggressively simply because someone carried it to a new area with the right mosquitoes? Zika virus got a foothold in the Americas, via Brazil, early last year. It is now present in 27 countries where it was previously unknown, across Asia, Africa and the Pacific. This includes the 12 countries in the Americas that have been infected since December alone (see page 6).