Oropouche virus causes acute hepatitis in mice controlled by Type I interferons.

Oropouche virus (OROV), a member of the Peribunyaviridae family endemic to South America, is a current public health threat. The recent OROV outbreak driven by a novel reassortant has caused a dramatic increase in cases in 2024 (13,785 in Brazil, versus only 261 from 2015-2022) with sustained levels of transmission in 2025. Previously underreported outcomes have been recognized including miscarriage, microcephaly, encephalitis, and death. OROV lethality in humans has been attributed to severe coagulopathy with liver involvement, and epidemiological data suggests acute hepatitis occurs in mild cases of Oropouche fever, highlighting the underrecognized role of the liver in OROV pathogenesis. We present two discrete mouse models of OROV hepatic disease - a lethal model that recapitulates the severe coagulopathy seen in fatal human cases and a model of self-resolving acute hepatitis which recapitulates mild human disease. OROV causes focal hepatic necrosis in mice, which progresses to massive necrosis and death when the Type I interferon receptor is antagonized. Additionally, we found a contemporary OROV isolate is less pathogenic in mice than a historic prototypical strain. These studies enhance our understanding of OROV pathogenesis and pave the way for potential therapeutic development and evaluation.