While everyone was paying attention to Zika, a much deadlier mosquito-borne virus began to spread

While the Zika outbreak was dominating the headlines, another mosquito-borne virus has taken hold in Africa: yellow fever. And with the large population of migrant Chinese workers in the affected area, scientists worry the disease could unleash its first outbreak in Asia. The authors of a recent paper called the current situation "unprecedented in history," writing that it is "critical" to assess the risk now and act quickly "so that a global catastrophe can be averted."  Yellow fever causes 180,000 cases and 78,000 deaths in Africa per year. It's spread throughout tropical areas of Africa and South America (where cases only number around a hundred per year) by the Aedes aegypti mosquito.