Chikungunya: Evolutionary history and recent epidemic spread

•Chikungunya virus evolved in Subsaharan Africa in transmission cycles involving arboreal mosquitoes and wild primates.•Emergence into urban transmission involving peridomestic mosquitoes has occurred repeatedly, probably for centuries.•The Asian and Indian Ocean lineages have recently spread to five continents, causing millions of cases of severe and often chronic arthralgia.•Based on failure since the 1950s to control dengue virus, the prospects for controlling urban CHIKV spread are poor.•The arrival of an Asian strain of CHIKV in the Americas in 2013 has dramatically increased the human populations at risk.

Chikungunya virus (CHIKV) has a long history of emergence into urban transmission cycles from its ancestral, enzootic, sylvatic foci in Sub-Saharan Africa, most recently spreading to the Americas beginning in 2013. Since 2004, reemergence has resulted in millions of cases of severe, debilitating and often chronic arthralgia on five continents. Here, we review this history based on phylogenetic studies, and discuss probable future spread and disease in the Americas. We also discuss a series of mutations in the recently emerged Indian Ocean Lineage that has adapted the virus for transmission for the first time by the Aedes albopictus urban mosquito vector, and compare CHIKV to other arboviruses with and without similar histories of urbanization. This article forms part of a symposium in Antiviral Research on “Chikungunya discovers the New World.”