The biology of chikungunya: a brief review of what we still do not know.

Responsible for a massive outbreak in the Indian Ocean in 2005-2006, the chikungunya virus is also reemerging in India where it has already infected over a million persons. Imported cases of the disease are reported in Asia, USA, and Europe, where a small epidemic occurred, due to transmission by local mosquitoes. Chikungunya virus is an alphavirus (Togaviridae family) that usually induces an acute illness characterized by fever, rash, and painful, incapacitating arthralgia a few days after being bitten by an infected mosquito, but recurrent joint pains are frequent. Unusual severe forms of the disease are also being reported that emphasize the importance of close monitoring of arboviruses in more fragile populations, such as the elderly and the newborns. Alphaviruses have generally been studied out of their epidemic context, leading to a large knowledge of their molecular features, and a much narrower understanding of their epidemiology and induced pathogenesis. Deciphering chikungunya virus specific molecular features as well as how the virus interacts with its vector and with its host are key to foresee, prevent and manage future epidemics, as well as prevent, treat or cure chikungunya disease.