Oropouche virus cases identified in Ecuador using an optimised qRT-PCR informed by metagenomic sequencing.

Oropouche virus (OROV) is responsible for outbreaks of Oropouche fever in parts of South America. We recently identified and isolated OROV from a febrile Ecuadorian patient, however, a previously published qRT-PCR assay did not detect OROV in the patient sample. A primer mismatch to the Ecuadorian OROV lineage was identified from metagenomic sequencing data. We report the optimisation of an qRT-PCR assay for the Ecuadorian OROV lineage, which subsequently identified a further five cases in a cohort of 196 febrile patients. We isolated OROV via cell culture and developed an algorithmically-designed primer set for whole-genome amplification of the virus. Metagenomic sequencing of the patient samples provided OROV genome coverage ranging from 68–99%. The additional cases formed a single phylogenetic cluster together with the initial case. OROV should be considered as a differential diagnosis for Ecuadorian patients with febrile illness to avoid mis-diagnosis with other circulating pathogens. Author summary: Oropouche virus (OROV) causes outbreaks of febrile illness in areas of South and Central America and we recently identified it in Ecuador for the first time, using metagenomic sequencing. The genome sequence data revealed that the Ecuadorian strain of the virus was not detected using a published qRT-PCR, as it differed genetically at the binding site of the reverse primer. To address this, we developed a modified qRT-PCR that showed increased sensitivity for the Ecuadorian strain. This test detected OROV infection in 6 out of 196 febrile patients from Esmeraldas, Ecuador in 2016. OROV was isolated from positive patient samples, viral genome sequences were compared to publicly available OROV sequences. This revealed that the Ecuadorian cases are genetically distinct, suggesting that local transmission of the virus should not be ruled out. This work highlights the need for a better understanding of OROV dynamics in Ecuador and surrounding areas, the importance of considering OROV as a cause of fever in Ecuadorian patients and the possibility of selectively using metagenomic sequencing in parallel to traditional molecular techniques in patient testing. [ABSTRACT FROM AUTHOR]

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