The emergence of chikungunya ECSA lineage in human settlements of the on the southern border of the Amazon forest, a Mayaro endemic region

Arboviruses impose large economic and public health burdens mostly in the tropical region of the world. Anthropic changes in the edge of the remaining tropical forest may facilitate the emergence of new viruses from the sylvatic environment and cocirculation of arboviruses with a sylvatic and urban cycle are expected to affect the human population. Thus, molecular surveillance is imperative in early detection of virus emergence and surveillance. In this study, we investigated the presence of arboviruses in sera of 354 patients showing clinical symptoms of arbovirus infection such as fever, myalgia, headache and arthralgia. Molecular surveillance was performed from February 2014 to October 2018 in Sinop city, on the southern border of the Amazon rainforest, Midwest Brazil. We sequenced the complete genome of one CHIKV-positive and one out of the 33 MAYV-positive samples. These genomes clustered with other viral strains from different Brazilian states. This is in line with other findings showing the rapid spread of the virus throughout the country. We found a small number of SNPs per sample varying from 17 to CHIKV and 29 to MAYV. We detected the E2 G60D mutation in the CHIKV genome, which might contributes to increased CHIKV fitness in Ae. albopictus and Ae. aegypti. We have also found five amino acid mutations reported to be under positive selection and to delineate the genotype L strains of MAYV. We reinforce the need for continued genomic surveillance strategies to track viral adaptations and to monitor CHIKV epidemics for improved public health control.