Oropouche fever is a tropical disease caused by infection with Oropouche virus. It is a zoonosis transmitted by biting midges and mosquitoes, from a natural reservoir which includes sloths, non-human primates, and birds. The disease is named after the region where it was first discovered and isolated in 1955, by the Oropouche River in Trinidad and Tobago.
Oropouche fever is endemic to the Amazon basin, with some evidence that its range may be spreading more widely in South and Central America. Since its discovery in 1955, there have been more than 30 epidemics of OROV in countries including Brazil, Peru, and Panama, with over half a million diagnosed cases in total. It has also been detected in-between epidemics, indicating that it may spread silently. It typically takes four to eight days (the incubation period) from the bite of the infected mosquito or midge to the first signs of infection. As in dengue, a skin rash resembling rubella, conjunctival injection, and pain behind the eyes may occur. Fetal deaths were observed possibly associated with vertical transmission, i.e. from mother to child.
Cause
The oropouche virus is an emerging infectious agent, which causes the illness oropouche fever.
OROV was first described in Trinidad in 1955 when the prototype strain was isolated from the blood of a febrile human and from Coquillettidia venezuelensis mosquitoes. In the Brazilian Amazon, oropouche is the second most frequent viral disease, after dengue fever. Several epidemics have generated more than 263,000 cases, of which half occurred in the period from 1978 to 1980. It is estimated that more than half a million cases have occurred since in Brazil alone, with most having gone undiagnosed or misdiagnosed due to limited availability of laboratory methods for diagnosis, the clinical similarity of Oropouche fever to other more prevalent arboviral illnesses, and the fact that in many cases there may be co-infection with other similar mosquito-borne viruses. By August 2024, over 8,000 laboratory-confirmed cases were reported in Bolivia, Brazil, Colombia, Cuba, and Peru, large outbreaks that resulted in travel-associated cases, including 19 Oropouche virus disease cases in European travelers returning from Cuba (n = 18) and Brazil (one) during June–July 2024, and 21 cases in U.S. residents returning from travel to Cuba (20 in Florida, one in New York). While most cases were characterized by mild self-limited febrile illness, two deaths were reported, both in non-pregnant women who were otherwise healthy.
Animal models
To further elucidate the pathogenesis of OROV, experiments using murine models have been performed.
BALB/c neonate mice were infected subcutaneously and presented clinical symptoms five days after inoculation. The mice revealed a high concentration of the replicating virus in the brain along with inflammation of the meninges and apoptosis of neurons without encephalitis, (obtained from recovered patients rich in anti- ORO antibodies)
- Reverse transcription polymerase chain reaction (RT-PCR) and real time RT-PCR for genome detection in acute samples (sera, blood, and viscera of infected animals) Aspirin and other non-steroidal anti-inflammatory drugs are not recommended for treatment. Ribavirin is ineffective and is not recommended.
Prognosis
The infection is usually self-limited and complications are rare. Illness usually lasts for about a week, although in extreme cases can be prolonged
See also
- 2023–2024 Oropouche virus disease outbreak