Oropouche virus disease

Person who presents with acute onset fever (or history of fever) of up to 5 days duration associated with intense headache and two or more of the following manifestations:

1. Myalgia or arthralgia
2. Chills
3. Photophobia
4. Dizziness
5. Retroocular pain
6. Nausea, vomiting or diarrhea (diarrhea is defined as three or more episodes in 24 hours and change in stool consistency)
7. Any nervous system manifestation (diplopia, paresthesia, meningitis, encephalitis, meningoencephalitis)

*It is important to note that up to 60% of Oropouche cases may experience a relapse of symptoms between 1 and 10 days after clinical improvement. In cases where Oropouche was not initially suspected, these patients should be reclassified as suspected cases. Given the clinical similarities between Oropouche and dengue, it is essential to conduct a thorough differential diagnosis, ensure close follow-up and monitoring, and assess for warning signs that may indicate dengue rather than Oropouche.

Headache is typically severe and often localized to the posterior (parieto-occipital) region. It commonly persists even after the fever subsides. A severe headache is defined as a pain score of 7 on a 1-to-10 scale. Myalgia and arthralgia are generally diffuse. Unlike chikungunya, arthralgia in Oropouche does not present with inflammatory signs. Patients frequently report neck pain and lower back pain.

Any suspected case that also presents any of the following criteria: 

1. Has a positive result for the detection of OROV, viral RNA (RT-PCR), or for viral antigens.
2. Presents an antibody seroconversion or an increase in antibody titer of at least 4 times in paired samples taken more than 7-10 days apart (and a convalescent sample taken more than 14 days after the onset of symptoms) (25).
3. Post-mortem determination of viral RNA by RT-PCR or demonstration of antibodies or antigens by immunohistochemical or other available tests in deceased patients with suspected OROV infection.
4. In cases of patients with suspected OROV encephalitis, the result of a positive IgM test in cerebrospinal fluid (CSF) is considered positive.

a. Pregnant women with signs and symptoms consistent with Oropouche infection with exposure in an area with potential circulation (travel or local exposure). 

• Recommend to follow the diagnostic testing algorithm.

OR 

b. Pregnant women with fetuses with findings of concern on prenatal images.

• Evidence of Central Nervous System defects (such as microcephaly, hydrocephaly) or hydrops.
• Recommend IgM testing of serum (knowing that it is not currently available everywhere)
• Consider RT-PCR testing of amniotic fluid (if appropriate)

a. Fetal demise/stillbirth in pregnant women with signs and symptoms consistent with Oropouche virus infection. 

b. Fetal demise/stillbirth with findings of concerns as evidence of central nervous system defects (such as microcephaly, ventriculomegaly, hydrocephaly) or other associated symptoms (arthrogryposis, macular atrophy), or hydrops.

Recommend testing:

• Fetal tissue, placenta, cord blood, CSF, serum or urine by RT-PCR
• Maternal serum for IgM, urine, and amniotic fluid for viral RNA by RT-PCR

a. Livebirths of mothers with laboratory evidence of Oropouche virus infection in pregnancy. 

• Recommend RT-PCR on serum and urine, and IgM testing on serum. 

OR

b. Livebirths with central nervous system defects such as microcephaly, ventriculomegaly, hydrocephaly or other associated symptoms (arthrogryposis, macular atrophy) or hydrops up to one year of age. 

Recommendations

• Clinician suspicion should be heightened for infants with cortical atrophy with minimal to no cortical calcifications and cystic lesions
• Recommend RT-PCR on serum and urine, and IgM testing on serum
• Consider RT-PCR  and IgM on CSF (if available)
• Maternal serum should be tested by IgM for serologic evidence of infection if not already testing
• Other infections should be considered and tested for