Re-emergence of chikungunya in the Republic of the Congo in 2019 associated with a possible vector-host switch.

• Identification of a chikungunya virus outbreak in a rural region in the Republic of the Congo. • Presence of the E1-A226V substitution in the circulating chikungunya virus strain. • Possible recent evolution of the A226V mutation and vector-host switch. In January 2019, an outbreak of chikungunya virus fever was reported in a rural region near Pointe-Noire, Republic of the Congo. Molecular and phylogenetic analysis of this new CHIKV strain demonstrated the presence of the A226V substitution and a surprisingly close relation with Aedes aegypti- associated Central Africa chikungunya strains. These results, combined with the preponderance of Aedes albopictus in the outbreak area, suggest a recent vector-host switch facilitated by the emergence and spread of the A226V mutation from a related CHIKV strain previously circulating in Aedes aegypti. The proximity of this outbreak to the large city of Pointe-Noire alerts us to a possibly devastating future outbreak in the absence of measures limiting the proliferation of Ae. albopictus mosquitoes. [ABSTRACT FROM AUTHOR]