Oropouche virus–specific antibodies were detected in more than 6% of tested serum samples across Latin America, indicating widespread but largely unrecognized transmission, according to a recent study.
Researchers conducted a large-scale, multidisciplinary study to identify predictors and transmission patterns of Oropouche virus (OROV) across Latin America. In the study, published in The Lancet Infectious Diseases, they combined retrospective serological testing, ecological modeling, and genomic analysis using over 9,400 serum samples collected between 2001 and 2022 from 76 provinces in Bolivia, Brazil, Colombia, Costa Rica, Ecuador, and Peru.
Serum samples were screened for OROV-specific immunoglobulin G (IgG) and immunoglobulin M antibodies using nucleoprotein-based enzyme-linked immunosorbent assays (ELISAs). A subset of 71 IgG-positive samples was further validated through plaque reduction neutralization testing. Among these, 83% demonstrated the highest neutralization titers against OROV, whereas 14% showed stronger reactivity to the reassortant Iquitos virus. The findings confirmed high ELISA specificity. IgG seropositivity was positively associated with increasing age, consistent with long-term antibody persistence following exposure.
The overall OROV-specific IgG detection rate was 6.3%, with marked heterogeneity across regions. Amazonian provinces showed seropositivity rates above 10%, while some high-altitude Andean areas reported rates below 1%. Seropositivity was observed in 57% of the provinces sampled. No statistically significant differences in detection rates were observed across cohort types or sex.
To assess regional transmission risk, the researchers, led by Carlo Fischer, MSc, of Charité–Universitätsmedizin Berlin, a corporate member of Freie Universität Berlin and Humboldt Universität zu Berlin, and of the Institute of Virology, used Maximum Entropy modeling with both serological presence–absence data and 2024 incidence data.
The serology-based model yielded stronger predictive performance, identifying high-risk areas in the Amazon River basin, southern Brazil, Central America, and the Caribbean. Climate-related variables, particularly isothermality and precipitation, contributed more than 60% to the models. Proximity to human settlements and evergreen land cover also contributed to risk estimates.
Genomic analyses revealed high sequence similarity among OROV strains, including a 2023 to 2024 Cuban outbreak isolate. Antigenic cartography showed minimal divergence between tested strains, whereas in vitro assays found no increased replication capacity in the outbreak strain. Plaque sizes for the Cuban isolate were smaller compared with those for other contemporary isolates.
The findings suggest that climatic and ecological conditions, rather than viral genetic changes, could be key drivers of OROV transmission. The researchers emphasized the need for enhanced diagnostics, targeted surveillance, and vector control to mitigate future outbreaks of this underrecognized arbovirus.
They reported no competing interests.