Previous outbreaks of CHIKV infection have been associated with the mosquito vector Aedes aegypti, which is also the vector of yellow fever and dengue viruses. However, Aedes albopictus has been the principal mosquito vector during many of the recent outbreaks of chikungunya associated with ECSA strains. 6 Analysis of CHIKV from the explosive outbreaks in Réunion and India revealed that the ECSA strains had acquired a point mutation resulting in a change from alanine to valine at position 226 in the E1 glycoprotein which enhanced the transmissibility of CHIKV in Aedes albopictus. 7 Subsequent studies demonstrated that amino acid changes in the E2 glycoprotein had a strong modulating effect on the E1: A226V change. 8

Until the outbreak of chikungunya in New Caledonia from February to June 2011, which was caused by Asianlineage CHIKV rather than the E1: A226V ESCA lineage, 9 Oceania had been free from chikungunya. During this outbreak, only 33 cases were detected, attributed to the onset of the cold season and the comprehensive control measures implemented after the diagnosis of the first cases.