Arrival of Oropouche Virus in a Nonendemic Area in Northeastern Brazil, 2024.

Orthobunyavirus oropoucheense (OROV) causes Oropouche fever, which exhibits symptoms similar to those of other arboviral diseases. Although it has historically been restricted to the Amazon region, the virus has recently spread to other areas of Brazil. Alagoas state, with low socioeconomic conditions and limited health coverage, has seen an increase in febrile cases without confirmed molecular diagnoses of circulating arboviruses. By September 6, 2024, 1316 samples negative for Dengue, Zika, and Chikungunya were tested for OROV and Mayaro virus using RT-qPCR, yielding 115 (8.74%) positive results for OROV. Among these, 14 (22.22%) viral isolates were obtained in Vero cells and confirmed by RT-qPCR and immunofluorescence assay (IFA). The study generated 37 new near-complete genomic sequences corresponding to the newly characterized OROV lineage and examined selection pressures on the M gene, identifying sites under purifying selection. We identified amino acid variations in the Gc glycoprotein structure at positions 507, 552, 738, and 795, which may influence host-cell interactions. This work is the first to report OROV in Alagoas, emphasizing the need for improved monitoring and control measures to mitigate public health impacts.