The risk of transfusion-transmitted infection: First evidence of Oropouche virus detection in an asymptomatic blood donor in Southeastern Brazil

OBJECTIVES: To report Oropouche virus (OROV) infections in asymptomatic blood donors who attended HEMORIO. METHODS: The BIO-MANGUINHOS MAYV/OROV Molecular Kit was used to screen samples from asymptomatic blood donations collected in Recreio dos Bandeirantes (February 10, 2025) and Barra Mansa (April 29, 2025), both located in Rio de Janeiro State. The samples were subsequently sent to the National Reference Laboratory for Arboviruses at the Evandro Chagas Institute (Pará State) for confirmatory molecular testing and genomic characterization using high-throughput sequencing (HTS). RESULTS: OROV RNA was detected in samples HRIO-1 and HRIO-3, with cycle threshold values of 39.58 and 28.99, respectively, in a pool of six plasma samples. HTS, using a probe-enrichment approach, enabled the recovery of one complete OROV genome from the HRIO-3 sample. Phylogenetic analysis showed clustering within the AMACRO II clade, forming a subclade with sequences from Rio de Janeiro, Espírito Santo, and Pernambuco. CONCLUSION: To the best of our knowledge, this is the first study to detect and genomically characterize, through whole-genome sequencing, OROV RNA in an asymptomatic blood donor in Southeastern Brazil.