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 fever infections in the Americas, originating from endemic areas in the Amazon basin and new areas in South America and the Caribbean. As of August 1, more than 8000 cases were reported from countries including Brazil, Bolivia, Peru, Colombia, and Cuba, with 2 deaths and 5 cases of vertical transmission associated with fetal death or congenital abnormalities reported. Travel-associated cases in the United States and Europe have been identified.

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 Oropouche virus become symptomatic. After an incubation period of about 1 week (3-10 days), patients will develop symptoms including periodic bouts of fever, headache (often with retro-orbital pain) and photophobia, nausea, vomiting, and muscle and joint pains, with up to 70% 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.