Key points
- Oropouche virus is spread to people primarily by the bite of infected biting midges. Some mosquitoes can also spread the virus.
- Oropouche virus has been reported in parts of South America, Central America, and the Caribbean. In June 2024, Cuba reported its first confirmed Oropouche case.
- Oropouche virus disease typically presents as an abrupt onset of fever, severe headache, chills, myalgia, and arthralgia.
- Clinical presentation is commonly mistaken for other arboviruses such as dengue, chikungunya, and Zika viruses, and malaria.
- There are no vaccines to prevent or medicines to treat Oropouche.
- Prevention relies on personal protective measures to avoid bites.
Epidemiology
Oropouche virus belongs to the Simbu serogroup of the viral genus Orthobunyavirus in the Peribunyaviridae family. The virus was first detected in 1955 in a febrile forest worker in a village in Trinidad and Tobago called Vega de Oropouche, near the Oropouche River. Oropouche virus is endemic to the Amazon basin.
Prior to 2000, outbreaks of Oropouche virus were reported in Brazil, Panama, and Peru. Evidence of animals being infected was also noted in Colombia and Trinidad during this time. In the last 25 years, cases of Oropouche have been identified in many countries in the Amazon region, including Bolivia, Brazil, Colombia, Ecuador, French Guiana, Panama, and Peru. One child was found to be infected in Haiti in 2014.
In late 2023, Oropouche virus was identified as causing large outbreaks in endemic areas and new areas in South America. In June 2024, Cuba reported its first confirmed Oropouche case. Currently, there is no evidence of local transmission in the United States.
Clinical features
The incubation period for Oropouche virus disease is 3–10 days. Typically, disease starts with the abrupt onset of fever (38-40°C) with headache (often severe), chills, myalgia, and arthralgia.
Other signs and symptoms include photophobia, dizziness, retroorbital or eye pain, nausea and vomiting, or maculopapular rash that starts on the trunk and goes to the extremities. Less common symptoms can include conjunctival injection, diarrhea, severe abdominal pain, and hemorrhagic symptoms (e.g., epistaxis, gingival bleeding, melena, menorrhagia, and petechiae).
Symptoms typically last less than a week (2–7 days). However, in up to 60% of patients, symptoms can reoccur a few days or even weeks later. Similar symptoms are reported on relapse.
The symptoms of Oropouche virus disease can be similar to symptoms of dengue, chikungunya, or Zika viruses, or malaria.
Abnormal laboratory findings
Abnormal laboratory findings have been documented in some patients with Oropouche virus disease including lymphopenia and leukopenia, elevated CRP (C-reactive protein), and mildly elevated liver enzymes. Thrombocytopenia also has been reported in a few cases.
Neuroinvasive disease
Oropouche virus can cause neuroinvasive disease (e.g., meningitis and encephalitis). It is estimated that up to 4% of patients will develop neurologic symptoms after their initial febrile illness. Symptoms reported for patients with neuroinvasive disease include intense occipital pain, dizziness, confusion, lethargy, photophobia, nausea, vomiting, nuchal rigidity, and nystagmus. Laboratory abnormalities noted in cerebrospinal fluid (CSF) for patients with neuroinvasive disease include pleocytosis and elevated protein.
Prognosis
Persistence of weakness and malaise has been noted in some patients for up to one month following symptom onset. Patients might require hospitalization for more severe signs and symptoms. Patients typically recover without long-term sequalae, including in severe cases. There have been very few deaths reported among people infected with Oropouche virus.
Vertical transmission
Causality of Oropouche virus disease and negative pregnancy outcomes has not been established. Viruses in the Simbu serogroup (e.g., Akabane virus) have been associated with fetal losses and deformities in cattle and sheep.
On July 17, 2024, the Pan American Health Organization (PAHO) issued an epidemiological alert about possible cases of pregnant mother-to-child transmission of Oropouche virus with adverse pregnancy outcomes in Brazil. These cases are under investigation. CDC is working with PAHO and other international partners to learn more about the potential risks of Oropouche during pregnancy.
Diagnosis
Preliminary diagnosis of Oropouche virus disease is based on the patient's clinical symptoms, location where infection likely occurred (including places and dates of travel), and activities leading to risk of possible exposure.
Evidence of the virus can be detected in serum samples during the first week of infection. The virus is readily cultured during the first few days of the infection and is usually not detected beyond day 5. However, viral RNA can be detected for several more days after the virus is no longer present. Toward the end of the first week of illness, IgM antibodies form, followed by IgG antibodies.
In patients with neuroinvasive disease, viral RNA can be detected but is often not present in CSF. Therefore, serologic testing is the preferred method to look for evidence of infection in the CSF. Viral RNA has been detected in saliva and urine of a patient 5 days into the illness. However, testing of these sample types is not currently validated or available in the United States.
Currently, CDC can perform plaque reduction neutralization tests (PRNTs) to detect virus-specific neutralizing antibodies in serum and CSF. To confirm a recent infection using serologic testing, both acute and convalescent samples are needed to document a 4-fold or greater change in antibody titers.
How to request testing
Contact your state or local health department if you have a patient with an acute illness and epidemiologic risk factors that might be compatible with Oropouche virus disease. They can assist you with determining if samples should be sent to the CDC Arbovirus Diagnostic Laboratory for further testing. Specimens should be submitted to CDC through state health departments. All results will be sent from CDC to the appropriate state health department.
Treatment
There are no medicines to treat Oropouche virus disease. Supportive care is recommended for clinical management of patients. Treatment for symptoms can include rest, fluids, and use of analgesics and antipyretics. Patients who develop more severe symptoms should be hospitalized for close observation and supportive treatment.
All patients with clinically suspected dengue should receive appropriate management without waiting for diagnostic test results. Patients should be advised to avoid aspirin containing drugs or other nonsteroidal anti-inflammatory drugs until dengue can be ruled out to reduce the risk of bleeding.
Prevention
The best way people can protect themselves from Oropouche is to prevent bites from biting midges and mosquitoes. There are no vaccines to prevent Oropouche virus disease. Additionally, there are no efficient, or economically or ecologically feasible, vector control measures for the primary vector, Culicoides paranesis.