Oropouche Virus (OROV)

 Overview

Oropouche disease is an emerging infectious disease caused by Oropouche virus (OROV), transmitted primarily through the bites of infected midges (Culicoides paraensis, colloquially called no-see-ums). First identified in Trinidad and Tobago in 1955, the range of OROV has been centered in Central and South America, particularly in the Amazon basin. The disease has recently expanded beyond traditional endemic areas, with over 10,000 cases reported in 2024, including new detections in Cuba, Haiti, and in travelers returning to the United States and Europe.

Approximately 60% of OROV infections are asymptomatic. Symptoms of OROV illness include flu-like symptoms such as sudden fever, severe headache, muscle and joint pain, nausea and vomiting, and sensitivity to light. The illness typically lasts 2-4 days, but symptoms may return about a week later in some patients. While most people recover completely, rare severe complications can include brain inflammation (meningitis or encephalitis), bleeding problems, and pregnancy complications. Recent reports suggest the virus may cause fetal death, stillbirth and birth defects including microcephaly when pregnant women are infected, much like zika virus.

There is currently no specific treatment or vaccine for OROV. Prevention focuses on avoiding insect bites through use of insect repellent, wearing long sleeves and pants, and habitat/breeding site reduction. Culicoides are daytime feeders that breed in standing water and congregate in rotting vegetation. Because of their small size, they pass through screens.

Prevention is mainly insect-bite avoidance, which is best accomplished by careful use of the DoD Insect Repellent System and Insect Repellent Treatment of Military Uniforms when traveling or deploying to areas with OROV transmission.  Women who are pregnant or planning to become pregnant should avoid travel to areas experiencing an OROV outbreak.  Current locations with OROV can be found here: CDC Oropouche Map.

Policy

Clinical Features

Oropouche disease typically presents after a 3-10 day incubation period with an acute febrile illness characterized by headache, arthralgia, myalgia, nausea, vomiting, chills, and photophobia. The disease is frequently biphasic, with an acute phase lasting 2-4 days, followed by remission and symptom recurrence 7-10 days after onset. Less common symptoms include rash, retro-orbital pain, and hemorrhagic manifestations. Approximately 60% of infections are asymptomatic. Severe OROV cases may progress to aseptic meningitis, meningoencephalitis, and Guillain-Barré syndrome, and recent case series have documented deaths associated with severe coagulopathy and liver failure.

Clinical symptoms are indistinguishable from other endemic arboviruses including dengue, Zika, chikungunya, and Mayaro virus. Co-infections with dengue, Zika, and chikungunya have been documented. Laboratory confirmation is essential for accurate diagnosis.
No specific antiviral therapy is available. Management is supportive, focusing on symptom relief with analgesics, antipyretics, and fluid management. Patients with neurological complications require appropriate supportive care and monitoring.

Congenital Oropouche Emerging evidence suggests that OROV can spread from a pregnant woman to her fetus during pregnancy or newborn around the time of birth. Infection during pregnancy has been associated with poor pregnancy outcomes such as stillbirth and birth defects, including congenital microcephaly. These findings are similar to what is seen with Zika virus, but far less is known about congenital OROV. Post-mortem examination of affected newborns has revealed severe viral meningoencephalitis. Data remains limited about the risks in context of the timing of exposure during pregnancy.

Diagnostics

There are limited options for commercial diagnostic assays. Most testing relies on in-house assays developed by reference laboratories. OROV is often underdiagnosed or misdiagnosed due to symptom overlap with other arboviral diseases and test unavailability.

BioFire does not currently have a panel that includes Oropouche virus. Diagnostic options for deployed personnel are limited. The lack of commercial multiplex platforms represents a significant diagnostic gap, particularly given that OROV symptoms are clinically indistinguishable from dengue, chikungunya and zika, necessitating laboratory confirmation for accurate diagnosis. The BioFire Global Fever panel can exclude Chikungunya and Dengue; DON diagnostic testing can also be performed at the Naval Infectious Disease Diagnostic Laboratory (NIDDL), which can potentially exclude dengue, chikungunya and zika: NIDDL Zika-Chik-Dengue-Zika Testing.

For suspected OROV cases in the U.S., testing is typically coordinated through state public health laboratories or the CDC. The CDC can perform RT-PCR testing for OROV on serum, plasma, CSF, saliva, or urine collected within 5 days of symptom onset, as well as serological testing for IgM antibodies. Paired PRNT (plaque reduction neutralization test) can increase diagnostic sensitivity by 45% compared to single-sample testing.

• For suspected OROV cases presenting ≤5 days after symptom onset: Collect serum/plasma for RT-PCR (preferred), with urine and/or whole blood as supplementary specimens to increase diagnostic yield. 
• For patients presenting >5 days after symptom onset: Collect urine for RT-PCR (may remain positive longer than serum) plus serum for IgM testing, with plans for convalescent serum at 2-4 weeks to demonstrate seroconversion. 

Reporting

Both non-congenital and congenital Oropouche virus disease are nationally notifiable diseases and non-congenital OROV must also be reported within DoD.  BUMEDINST 6220.12D  requires that all cases of OROV be reported to Preventive Medicine authorities in the Disease Reporting System internet (DRSi). Case classification details are fully described in the Armed Forces Medical Reportable Events Guide (note: OROV is listed under “Arboviral Disease, Neuroinvasive and Non-neuroinvasive”). Detailed information on reporting in DRSi can be found on NMCFHPC’s Medical Surveillance and Reporting page.  

Additionally, notify your cognizant  Navy Environmental and Preventive Medicine Unit (NEPMU), which can help guide mitigation efforts.

Public Health

Surveillance

Enhanced awareness and surveillance of OROV is essential given its expanding geographic range and its status as an emerging infection. Because both the primary and suspected secondary vectors are present beyond South and Central America, further global dissemination is likely. This concern extends to spread within the United States following introduction.  Healthcare providers should consider OROV in the differential diagnosis of febrile illnesses, neurological manifestations, and pregnancy complications in OROV endemic regions and in returning travelers.

Transmission and Prevention

Vector-borne Transmission: The biting midge Culicoides paraensis is the main vector of OROV, with potential secondary involvement of some mosquito species such as Culex quinquefasciatus. In forested areas, OROV often originates from wild vertebrate hosts including sloths, non-human primates, wild birds, and rodents, with spillover into human populations that live nearby. In urban areas, once OROV is introduced it is maintained directly between midges and human hosts. Prevention of insect bites is the primary prevention measure for OROV(see below).
 
Vertical Transmission: Vertical transmission of OROV from mother to fetus or infant is documented, but there is still very little known about infection during pregnancy. Fetal loss, stillbirth and congenital abnormalities, including microcephaly, have been reported. Pregnant travelers should be counseled about potential risks and advised to re-consider travel to areas with a Level 2 Travel Health Notice for Oropouche. CDC Travel Health Notices

Sexual transmission: There is also limited evidence demonstrating viral shedding in semen, suggesting the possibility for sexual spread as is seen with zika.  Currently, the risk is hypothetical and there have been no cases of OROV determined to be sexually transmitted. Nonetheless, CDC recommends that male patients recovering from OROV use precautions (e.g., abstinence or condom use) for 6 weeks after symptoms. Furthermore, all travelers with symptoms of OROV should consider abstinence or condom use for 6 weeks to avoid potential risk of spread.  CDC Oropouche Prevention Tips

Insect Bite Avoidance and Vector Control

OROV disease prevention relies on vector control strategies and personal protection measures to avoid insect bites. OROV is primarily transmitted by midges (“no-see-ums”), which are markedly smaller than mosquitos and pass easily through netting. Repellents and permethrin-treated clothing remain effective.

• Apply 25-30% DEET or 20% picaridin based repellents on exposed skin and treat clothing with a permethrin-containing product.
• Wear long-sleeved light-colored shirts and pants whenever outdoors or in places where mosquitoes may be present.
• Reduce the number of breeding areas by removing water from containers around buildings and draining areas of standing water.
• Limit vegetation and agricultural waste around buildings to prevent overgrowth and potential midge harborages.

Risk Communication: Consider working with Public Affairs to implement an OROV public awareness campaign if cases are found locally.
Support: The cognizant  Navy Environmental and Preventive Medicine Unit (NEPMU) can advise on and/or assist with case investigation activities and vector control measures. The Navy Entomology Center of Excellence (NECE) provides specialized operational entomology support and offers courses for pesticide applicator certification.

Web Resources

Epi and Selected Publications

ArboNet US Oropouche Data
Lorenz C, de Azevedo TS, Sallum MAM, Chiaravalloti-Neto F. Oropouche fever outbreak in Brazil: Key factors behind the largest epidemic in history. PLoS One. 2025 Jul 28;20(7):e0327845. doi: 10.1371/journal.pone.0327845. PMID: 40720414; PMCID: PMC12303302.

Morrison A, White JL, Hughes HR, et al. Oropouche Virus Disease Among U.S. Travelers — United States, 2024. MMWR Morb Mortal Wkly Rep 2024;73:769–773. DOI: http://dx.doi.org/10.15585/mmwr.mm7335e1

Pastula DM, Beckham JD, Tyler KL. Oropouche Virus: An Emerging Neuroinvasive Arbovirus. Ann Neurol. 2024 Nov 19:10.1002/ana.27139. doi: 10.1002/ana.27139. Epub ahead of print. PMID: 39560215; PMCID: PMC12626173.