Genomic and phenotypic characterization of the Oropouche virus strain implicated in the 2022-24 large-scale outbreak in Brazil.

The Orthobunyavirus oropoucheense species encompasses a group of arthropod-borne zoonotic viruses transmitted by biting midges to animals including humans. Several large-scale human outbreaks caused by the prototype member of this species, Oropouche virus (OROV) have been documented since the 1970s and were primarily confined to the Amazon basin. However, since 2022, more widespread OROV outbreaks have been unfolding in Brazil and across South America, with cases exported to Cuba, Italy, Spain, USA and Germany. In Brazil, the virus has reached and established communitary transmission in all geographic areas of the country. We isolated, characterized the cytopathic effect and recovered the full genome of two OROV isolates from the 2022-24 outbreak detected in patients from the Pernambuco state. Phylogenetic data supports a direct introduction from the Amazonas state, the epicenter of the epidemics in the country. As case counts accumulate in the state mounting evidence is supporting the establishiment of sustained transmission chains. Continued studies are critical to understand the transmission cycle in this region, including the most important vectors and reservoirs, to appropriately deploy control measures.