Large number of imported chikungunya cases in mainland France, 2014: a challenge for surveillance and response.

During the summer of 2014, all the pre- requisitesfor autochthonous transmission of chikungunyavirus are present in southern France: a competent vector, Aedes albopictus, and a large number of travellers returning from the French Caribbean islandswhere an outbreak is occurring. We describe the system implemented for the surveillance of chikungunyaand dengue in mainlandFrance. From 2 May to 4 July 2014, there were 126 laboratory-confirmed imported chikungunyacases in mainlandFrance.