Oropouche virus disease
Source: gov.uk (2025-06-26)

Clinical advice on the diagnosis of Oropouche virus disease.

Background

Oropouche virus is an RNA virus belonging to the Orthobunyavirus genus. It was first identified in 1955 in Trinidad and Tobago, and subsequently in the Amazon basin where it is considered to be endemic. Since 2023 there has been an increase in cases, with outbreaks reported in Brazil, other countries in South America, and the Caribbean. A small number of travel-associated cases have been reported in the USA and Europe, including the UK.

Oropouche virus disease (also known as Oropouche fever) is transmitted by certain species of midges (Culicoides paraensis) and mosquitoes (for example, Culex quinquefasciatus). These insects are not present in the UK. It can cause an influenza-like infection with:
- fever
- headache
- joint pain
- muscle pain
- chills
- nausea
- vomiting
- rash
Most people recover on their own, but occasionally it can cause severe disease, particularly in the very elderly or immunosuppressed. Currently there is no specific vaccine or antiviral treatment, and management is supportive with antipyretics, painkillers and maintenance of fluid balance.

The World Health Organization (WHO) have reported possible fetal infection (https://www.paho.org/en/documents/epidemiological-alert-oropouche-region-americas-vertical-transmission-event-under) transmitted from women infected during pregnancy. A recent study (https://wwwnc.cdc.gov/eid/article/30/12/24-1470_article) has also reported Oropouche virus in the semen of an infected patient, which raises the possibility of infection being transmitted though unprotected sex.

Testing

Testing is available through the Rare and Imported Pathogens Laboratory (RIPL) (https://www.gov.uk/government/collections/rare-and-imported-pathogens-laboratory-ripl)

Testing should be considered in patients who have a compatible clinical syndrome along with epidemiological risk factors. Testing is not currently recommended for asymptomatic patients, or patients without a relevant travel history.

Testing in pregnancy

Current testing recommendations are the same for pregnant and non-pregnant women. Testing is not currently recommended in the absence of symptoms. Contact the Imported Fever Service (https://www.gov.uk/guidance/imported-fever-service-ifs) xx-xxxx-xxxx) if you are concerned about possible Oropouche infection in a pregnant patient.

Tests available at RIPL

Polymerase Chain Reaction (PCR) and serological testing (IgM and IgG) are available at RIPL, however, note that these are developmental assays and are not within our UKAS accreditation scope. This is because of the limited number of samples available for full validation outside of the affected countries.

Patients are viraemic in the first few days of illness. IgM antibodies appear at the end of the first week of illness, followed by IgG. PCR testing can therefore be done on samples taken within 7 days of the onset of illness. For samples taken after this, serological testing will be performed if indicated by the clinical details. Specify the date of onset of illness, along with the sample date, when sending samples to RIPL. We will require acute and convalescent samples to confirm seroconversion in keeping with recent infection.

For most patients, the symptoms and risk factors for Oropouche virus disease will be similar to other vector-borne viruses such as dengue and Zika. Testing will usually be done for these infections first, with Oropouche testing reserved for those with negative results for the more common viruses. Contact the Imported Fever Service (https://www.gov.uk/guidance/imported-fever-service-ifs) xx-xxxx-xxxx) to discuss if there is a high index of suspicion for Oropouche virus disease.

Sample type

PCR and serology can be done on a serum sample. PCR can also be done on a plasma sample.

Cerebrospinal fluid (CSF) testing may be considered for patients with neurotropic symptoms. PCR may be negative in CSF even with neurological symptoms and therefore serological testing of CSF would be required, however, this is a developmental assay and very limited validation has been performed on this sample type. Contact the RIPL clinical team to discuss before sending a CSF sample.

Biosafety

Oropouche virus is a hazard group 2 pathogen and potentially infectious material should be handled at containment level 2. Samples can be sent using a category B courier.