Oropouche fever is an arthropod-borne virus in the family Peribunyaviridae that was first identified in Trinidad and Tobago in 1961. Since that time, there have been several outbreaks in Central and South American countries and more than 500 000 cases have been diagnosed, although the true number of infections is likely underreported due to underdiagnosis.

In 2024, there has been a surge of Oropouche virus (OROV) infections in the Americas, originating from endemic areas in the Amazon basin and new areas in South America and the Caribbean. As of October 15, more than 10 000 cases were reported from countries including Brazil, Bolivia, Peru, Colombia, Cuba, Ecuador, and Guyana, with 2 deaths and more than 20 cases of vertical transmission associated with spontaneous miscarriage, fetal death, or congenital anomalies reported. Travel-associated cases in the United States, Canada, and Europe have been identified; most, but not all, cases in the United States have been identified in Florida.

Oropouche fever is transmitted to humans through the bite of infected midges (Culicoides paraensis) that inhabit tropical forested areas and waterfronts with high frequencies of rainfall. Outbreaks in nearby urban centers have also been reported, often in the setting of rapid urbanization and climate change. Animal reservoirs for the virus may include nonhuman primates, sloths, birds, and mosquitoes. Transmission from viremic humans to uninfected humans via biting midges has been described as well. Vertical transmission has been reported.

About 60% of people infected with OROV become symptomatic. After an incubation period of about 1 week (4-8 days), patients will develop symptoms including periodic bouts of high fever, headache (often located in the nape of the neck or with retro-orbital pain) and photophobia, dizziness, nausea or vomiting, extreme weakness (prostration), and muscle and joint pains, including low back pain, with up to 60% of patients developing recrudescent symptoms up to 14 days after initial recovery. The infection generally self-resolves within 2-3 weeks. A rubella-like rash has been described, albeit less frequently. More severe (and rarer) cases involving bleeding diathesis (petechiae, epistaxis, or gingival bleeding) or neurologic complications (meningitis and encephalitis) have been reported. No deaths had been attributed to Oropouche fever until 2024.