2025-06-09-世界卫生组织-Risk_evaluation_of_Oropouche_virus_and_its_reassortants_14页_376kb

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Risk Evaluation of Oropouche Virus and Its Reassortants Summary

Introduction

This document summarizes the current evidence and risk evaluations for Oropouche virus (OROV) and its reassortants up to May 2025. It highlights control measures, identifies knowledge gaps, recommends studies, and assesses public health risks based on WHO consultations.

Emergence, Epidemiology, and Transmission

OROV is an arbovirus causing Oropouche fever, first discovered in 1955, with outbreaks in Central and South America and the Caribbean.
Recent outbreaks have expanded geographically, including Brazil, Cuba, Bolivia, Colombia, Ecuador, Guyana, Panama, Peru, and cases in Europe linked to travel.
Primary transmission occurs via Culicoides paraensis biting midges; climate change may increase risks by expanding vector distribution and activity.
Sylvatic and epidemic transmission cycles involve humans and animals, with limited data on species involved.

Circulating OROV Lineages

Two main reassortants identified: BR-2015-2024 (circulating in Brazil and Cuba) and PE/CO/EC-2008-2021 (in Peru and Ecuador).
Co-circulation in regions like Brazil and Peru suggests ongoing reassortment events; the BR-2015-2024 likely emerged in the Amazonas state.

Reassortment affects evolution, particularly the M segment coding for glycoproteins.

Vector Distribution and Competence

Primary vector is Culicoides paraensis, thriving in tropical environments; climate change may facilitate range expansion.
Other potential vectors like C. sonorensis or mosquitoes (e.g., Culex quinquefasciatus) show low transmission efficiency.
Vertical transmission suspected in rare cases; sexual transmission possible but not documented.

Clinical Disease and Risk Assessment

Symptoms include fever, headache, myalgia; generally self-limiting, with rare neurological complications.
Case fatality ratio is very low (around 0.02% in 2024), but pregnancy risks include vertical transmission and congenital malformations.
Overall risk is low outside Americas; moderate in endemic areas with competent vectors.

Control and Surveillance

Preventive measures include vector control (e.g., environmental management) and personal protection (repellents, clothing).
Surveillance prioritizes detecting OROV in patients with Dengue-like illness; diagnostic methods focus on RT-PCR.
Recommended studies include ecological research on vectors, serological surveys, and clinical studies on vertical transmission and immune evasion.

Gaps and Recommendations

Key gaps: limited data on animal reservoirs, vector ecology, and pregnancy outcomes.
WHO recommends targeted research, enhanced surveillance, and preparedness, including blood safety monitoring and reassessment of risks with climate shifts.

*Overall risk remains low in non-endemic areas, with focus on regions with rising transmission due to vectors.

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