Oropouche virus: transmission, epidemiology, genetic diversity, and public health implications

Historically endemic to parts of South America, Oropouche virus (OROV) has caused an estimated 500,000 infections since its discovery, with a marked geographic expansion beyond the Amazon basin into other regions of South America and the Caribbean since late 2023. This Review synthesises current evidence on OROV epidemiology, transmission dynamics, clinical manifestations, diagnostics, viral diversity, and public health impact, with the primary objective of identifying critical knowledge gaps and outlining priorities for surveillance, research, and control. Human transmission occurs primarily via Culicoides paraensis midges, while the competence of other vectors, the role of animal reservoirs in sustaining sylvatic transmission, and the contribution of vertical and sexual transmission remain incompletely understood. Although most infections are self-limiting, reports of neurological disease, Guillain-Barré syndrome, adverse pregnancy outcomes, and rare fatalities highlight uncertainties regarding pathogenicity, risk factors for severe disease, and long-term sequelae. The known teratogenicity of related Simbu serogroup orthobunyaviruses in animals further raises concerns about foetal risk in humans. Environmental change, expanding vector ranges, and viral evolution are likely contributing to outbreak emergence and geographic spread. Based on the available evidence, this review highlights priority gaps in epidemiological surveillance, diagnostics and genomic monitoring, vector competence and ecology, transmission pathways, and countermeasure development. Addressing these gaps through coordinated surveillance, improved laboratory capacity, targeted vector control, and focused research will be essential to mitigate the public health impact of OROV and reduce the risk of further spread.