Clinical Overview of Oropouche Virus Disease

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, including Argentina, 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. For the latest information, see Countries and Territories with Recent or Previous Oropouche Virus Transmission. Currently, there is no evidence of local transmission in the United States.

Clinical features

The majority of people infected with Oropouche virus become symptomatic. 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.

Guillain-Barré syndrome

A published report describes three patients who developed Guillain-Barré syndrome (GBS) following infection with Oropouche virus. All three patients had an acute febrile illness and specimens that were RT-PCR positive for Oropouche virus and subsequently developed GBS 10–11 days after initial symptom onset. The patients were hospitalized for 3 to 4 weeks and were discharged without apparent sequelae. While these are the first reports of GBS following Oropouche infection, GBS is associated with other viral infections, including those caused by arboviruses.

CDC is working with international partners to learn more about the possible association between GBS and Oropouche infection.

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

On July 17, 2024, the Pan American Health Organization (PAHO) issued an epidemiological alert about cases in Brazil of vertical transmission of Oropouche virus associated with adverse pregnancy outcomes, including fetal deaths and congenital abnormalities. CDC is working with PAHO and other international partners to learn more about the risks of Oropouche during pregnancy. CDC has drafted Interim Clinical Considerations for Pregnant People with Confirmed or Probable Oropouche Virus Disease.

Counseling pregnant patients

Healthcare providers should be aware of the risk of vertical transmission and possible adverse impacts on the fetus, including fetal death or congenital abnormalities.

Inform pregnant people of the possible risks to the fetus when considering travel to areas with reported Oropouche virus transmission. Counsel these patients to consider the destination, reason for traveling, and their ability to prevent insect bites.

Pregnant people are currently recommended to reconsider non-essential travel to areas with a Level 2 Travel Health Notice for Oropouche. If a pregnant person decides to travel, counsel them to strictly prevent insect bites during travel.

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. Although there is no specific treatment for Oropouche virus disease, testing patients with suspected disease is recommended to:

• Determine the best course of clinical management (e.g., avoiding nonsteroidal anti-inflammatory drugs, avoiding unnecessary treatments and procedures, monitoring the patient for severe symptoms or complications).
• Counsel the patient on prevention (e.g., avoiding mosquito bites, blood donation, possible sexual transmission).
• Provide important information about where viruses are circulating and risk of infection for other patients.

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 real-time reverse transcription-polymerase chain reaction (RT-PCR) to detect viral RNA in serum and CSF during the acute phase of the illness. CDC also 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.

Limited published data on the possible risk of adverse pregnancy outcomes in asymptomatic pregnant persons with evidence of Oropouche does not support a routine testing recommendation. However, healthcare providers can contact their local or state health departments for consultation if an asymptomatic pregnant person who traveled to or lived in an area with document or suspected Oropouche has fetal findings concerning for congenital Oropouche or experiences a stillbirth. Your health department can arrange testing or consultation with CDC if circumstances warrant it.

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 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.

Infection prevention and control

Laboratory, healthcare, and other workers exposed to blood, other body fluids, or cultures of infected individuals may be at risk for Oropouche virus exposure. Healthcare personnel should follow Standard Precautions for all patient care and laboratory personnel should follow standard laboratory procedures.

Possible sexual transmission

A recent scientific report describes the first time Oropouche virus was found in semen of a patient who had Oropouche, which raises concern about the possible risk of sexual transmission. Viruses (e.g., Zika virus, Ebola virus) in semen have been associated with sexual transmission of other infectious diseases. No cases of sexual transmission of Oropouche virus have been reported. CDC has interim recommendations for travelers to areas with a Level 1 or 2 Travel Health Notice for Oropouche to prevent possible transmission during sex.

Blood donation

CDC has not yet determined if Oropouche virus poses a risk to the blood supply. At this time, no cases of blood transfusion transmission of Oropouche virus have been identified. Evidence of the virus can be detected in serum during the first week of infection, but virus and antibody dynamics are currently not well understood. Until more is known about Oropouche virus, FDA suggests people diagnosed with Oropouche virus disease should consult with their blood donation center and consider not donating blood for at least 4 weeks. People diagnosed with Oropouche virus disease shortly after giving blood should tell their blood center.