Oropouche virus is an arbovirus of genus Orthobunyavirus (family Peribunyaviridae) in the Simbu serogroup. It is mainly transmitted to people by Culicoides paraensis biting midges and occasionally mosquitoes, and it causes a febrile illness known as Oropouche fever.
Biology and Transmission
The Oropouche virus has a tripartite negative‑sense RNA genome with S, M and L segments encoding the nucleocapsid and envelope proteins. It circulates in both sylvatic and urban cycles involving sloths, primates, birds and biting insects. The primary vector is the midge Culicoides paraensis, which supports urban transmission; mosquitoes such as Culex quinquefasciatus and Aedes serratus may also act as vectors. Humans are incidental hosts; most infections follow the bite of an infected midge, and there is no evidence of sustained human‑to‑human transmission. The virus has multiple genotypes and an incubation period of three to ten days.
Outbreaks and Clinical Features
Oropouche fever presents as a sudden onset of fever, intense headache, myalgia, arthralgia, chills, nausea, vomiting and sometimes a rubella‑like rash. Most cases resolve within a week, but some patients experience prolonged convalescence. Rare complications include aseptic meningitis, photophobia and mild bleeding. Since the virus was first isolated in 1955, more than thirty outbreaks have been recorded in Brazil and neighbouring countries. Between January and August 2024 over eight thousand cases were reported in Peru, Brazil, Colombia, Bolivia and Cuba, with a few deaths and evidence of vertical transmission leading to fetal loss. Imported cases have occurred in travellers to Europe and North America, highlighting the potential for spread. Oropouche virus is an emerging threat in tropical America. Although most infections are self‑limited, the increasing number of outbreaks and the virus’s adaptation to urban transmission underscore the need for surveillance, vector control and research into vaccines and diagnostics. Related Terms: La Crosse virus, California encephalitis virus, Jamestown Canyon virus, Mayaro virus, Orthobunyavirus