Table 2 Overview of epidemiology, transmission, and clinical presentation of Oropouche virus

Incidence

OROV incidence is likely underestimated due to clinical similarities with other arboviral infections, lack of systematic surveillance, and limited lab diagnostics. Outbreaks are often identified through retrospective investigations.

Factors Contributing to Spread

Urbanization, deforestation, human activity in the Amazon Basin, and population migration increase OROV risk. Vectors like Culicoides paraensis are more likely to spread due to increased interaction with reservoir hosts in peri-urban and urban areas.

Impact of Health Systems and Migration

Fragile health systems and complex humanitarian crises further exacerbate the spread of OROV, especially in areas with large population migrations and limited healthcare infrastructure.

Reservoir Hosts & Sylvatic Cycle

Bradypus tridactylus (sloths), nonhuman primates, and wild birds act as vertebrate hosts in the sylvatic cycle. The sylvatic vector remains unclear, but Ochlerotatus serratus and Coquilletidia venezuelensis were isolated in the Amazon region and Trinidad, respectively.

Urban Cycle Vectors

Humans are the only known vertebrates in the urban cycle. Culex p. quinquefasciatus and Culicoides paraensis are identified as urban vectors, though Culex is considered a less efficient vector based on laboratory studies.

Experimental Transmission Evidence

Culicoides paraensis can transmit OROV to hamsters after feeding on humans. These midges are highly aggressive and prevalent in tropical and subtropical areas. The virus can be transmitted via midge bites 3–4 days after the onset of symptoms.

Incubation and Transmission

Incubation is suspected to be 4–8 days. Viremia occurs within the first 3–4 days of symptom onset, with no evidence of direct human-to-human transmission.

Hemorrhagic Manifestations

Although they are uncommon, hemorrhagic symptoms can include petechiae, epistaxis, and gingival bleeding in certain people. The disease’s clinical presentation is further complicated by these characteristics.

Clinical Manifestations

OROV infection presents as an acute febrile illness with symptoms like headache, myalgia, arthralgia, anorexia, dizziness, chills, and photophobia. Additional symptoms include nausea, vomiting, diarrhea, and conjunctival congestion. About 60% of cases experience symptom recurrence. Severe cases may involve meningitis, and there is potential CNS involvement in some cases.