The importance of entomo-virological investigation of yellow fever virus to strengthen surveillance in Brazil

The largest outbreak of sylvatic yellow fever virus (YFV) in eight decades was recorded in Brazil between 2016-2018. Besides human and NHP surveillance, the entomo-virological approach is considered as a complementary tool. For this study, a total of 2904 mosquitoes of the 'Aedes', 'Haemagogus' and 'Sabethes' genera were collected from six Brazilian states (Bahia, Goias, Mato Grosso, Minas Gerais, Para, and Tocantins) and grouped into 246 pools, which were tested for YFV using RT-qPCR.We detected 20 positive pools from Minas Gerais, 5 from Goias, and 1 from Bahia, including 12 of 'Hg. janthinomys' and 5 of 'Ae. albopictus'. This is the first description of natural YFV infection in this species and warns of the likelihood of urban YFV re-emergence with 'Ae. albopictus' as a potential bridge vector. Three YFV sequences from 'Hg. janthinomys' from Goias and one from Minas Gerais, as well as one from 'Ae. albopictus' from Minas Gerais were clustered within the 2016-2018 outbreak clade, indicating YFV spread from Midwest and its infection in a main and likely novel bridging vector species. Entomo-virological surveillance is critical for YFV monitoring in Brazil, which could highlight the need to strengthen YFV surveillance, vaccination coverage, and vector control measures.