Evidence for current circulation of an ancient West Nile virus strain (NY99) in Brazil

Introduction In Brazil, West Nile virus (WNV) was first detected in 2018 from horses with neurological disease. Aim Here we present the first reported case in Ceará state and complete genome sequence from an isolated in Espírito Santo state from 2019. Methods The virus was isolated from a horse that died with neurological signs in Espírito Santo and was sequenced by MiSeq. Results Phylogenetic analysis reveals that this isolate belongs to lineage 1a, clustering with NY99 strain, that disappeared from the USA since 2005. Conclusions Our findings reinforce the hypothesis that WNV has been silently circulating in Brazil for many years.