Risks to the Americas associated with the continued expansion of chikungunya virus.

Chikungunya virus is a mosquito-borne virus that has been responsible for over 2 million human infections during the past decade. This virus, which previously had a geographical range primarily restricted to sub-Saharan Africa, the Indian subcontinent and South East Asia, has recently moved to subtropical latitudes as well as the western hemisphere. This expansion into novel habitats brings unique risks associated with further spread of the virus and the disease it causes.