Science 361, 894–899 (2018).

Yellow fever is a severe mosquito-borne virus of the Flaviridiae family. It may be transmitted both through a cycle involving nonhuman primates and mosquitoes (known as sylvatic transmission) and a cycle involving humans and mosquitos in urban areas. Brazil has recently had its largest recorded yellow fever outbreak in decades, and new surveillance is required to track transmission route, as urban transmission could be particularly devastating.

In a collaboration between many international scientists, epidemiological, spatial and genomic approaches are combined to characterize yellow fever transmission in the recent outbreak in Brazil. Their results indicate that sylvatic transmission occurred initially, followed by spillover to human areas.

The authors’ approach provides a framework for monitoring future epidemics to strategize intervention approaches.