This study aimed to investigate the circulation of Orthobunyavirus species in the state of Mato Grosso (MT)
Brazil. During a dengue outbreak in 2011/2012, 529 serum samples were collected from patients with acute febrile
illness with symptoms for up to five days and 387 pools of female Culex quinquefasciatus
captured in 2013 were
subjected to nested-reverse transcription-polymerase chain reaction for segment S of the Simbu serogroup followed
by nucleotide sequencing and virus isolation in Vero cells. Patients (5/529; 0.9%) from Cuiabá (n = 3), Várzea
Grande (n = 1) and Nova Mutum (n = 1) municipalities were positive for the S segment of Oropouche virus (OROV).
Additionally, eight/387 Cx. quinquefasciatus
pools were positive for the segment, with a minimum infection rate of
2.3. Phylogenetic analysis indicated that all the samples belong to the subgenotype Ia, presenting high homology
with OROV strains obtained from humans and animals in the Brazilian Amazon. The present paper reports the first
detection of an Orthobunyavirus, possibly OROV, in patients and in Cx. quinquefasciatus
mosquitoes in MT. This
finding reinforces the notion that arboviruses frequently reported in the Amazon Region circulate sporadically in
MT during dengue outbreaks.