Chikungunya virus (CHIKV) is a mosquito-borne pathogen that has re-emerged to become a significant global disease threat. Although CHIKV has historically been associated with localized outbreaks of debilitating polyarthralgia in Africa and Asia, factors such as increased global travel and viral adaptation to new mosquito vectors have led to the introduction and spread of CHIKV in new regions of the world, including the Americas. The re-emergence of CHIKV has stimulated significant interest both in understanding the biology of CHIKV andin the development of medical countermeasures against the virus.