2013-04-23-世界卫生组织-China—WHO_Joint_Mission_on_Human_Infection_with_Avian_Influenza_A_H7N9_Virus,_18_–_24_April_2013_51页_458kb

China- WHO Joint Mission on Human Infection with Avian Influenza A(H7N9) Virus (18-24 April 2013)

Executive Summary

• Event: China reported three human cases of novel influenza A(H7N9) virus infection on 31 March 2013.
• Joint Mission: Formed by China and WHO to assess the outbreak and provide management guidance.
• Key Findings:
  • H7N9 virus detected in Shanghai and Anhui provinces, primarily affecting older males.
  • Strong association with live poultry exposure (live bird markets).
  • Limited evidence of human-to-human transmission (no sustained cases).
  • Severe disease in cases with rapid deterioration; virus shows mammalian adaptations.
• Response: Effective multi-sectoral coordination; closure of live bird markets in Shanghai reduced new cases.
• Recommendations: Focus on source identification; enhance surveillance; promote international collaboration.

Key Points

Epidemiology

• Cases: 104 confirmed by April 22, 2013 (median age 62 years; ~70% male).
• Risk Factors: Direct exposure to live poultry or contaminated environments.
• Clusters: Three family clusters; no confirmatory evidence of sustained human-to-human transmission.
• Surveillance: Enhanced case finding; NAI treatment initiated late (~6 days post-onset).

Characteristics of Avian Flu A(H7N9) Viruses

• Genome: Reassortant virus with H7 HA, N9 NA, H9N2 internal genes.
• Adaptation: Possesses PB2 E627K (human-like replication); sensitive to NA inhibitors (oseltamivir/zanamivir).
• Pathogenicity: Not highly pathogenic in poultry but severe in humans; partial immunity in poultry may exist.

Animal Health

• Detection: H7N9 found in poultry and environments at live poultry markets.
• Surveillance: Extensive sampling; closure of markets associated with reduced human cases.
• Trade: Virus likely spread via intra-/inter-provincial poultry trade.

Response Strategies

• Coordination: Joint multi-sectoral mechanism at national and local levels.
• Surveillance: Enhanced human/animal monitoring; distribution of PCR diagnostics to ~400 labs.
• Clinical Management: Early NAI use prioritized, evolving guidelines for severe cases.
• Infection Control: Compliance with national/WHO protocols; PPE used.

International Collaboration

• Data Sharing: Timely reporting to WHO; global collaboration enabled accelerated analysis.
• Vaccine/Reagent Development: Virus shared with WHO CCs; contributed to candidate vaccine selection.

Risk Assessment & Recommendations

• Risk Level: Unusually high potential for human infection and transmissibility.
• Recommendations:
  1. Intensify source investigation.
  2. Maintain preparedness.
  3. Expand surveillance and research.
  4. Strengthen cross-sectoral collaboration.
  5. Continue global virus sharing.

Annexes Overview

• Detailed findings, genetic analyses, surveillance protocols, timeline, and method of mission included.
• Consolidated recommendations emphasize global preparedness and response coordination.

Conclusions and Recommendations Summary

• Effective Initial Response: China’s timely actions demonstrated preparedness.
• Key Risk: H7N9 represents a severe threat due to efficient human adaptation, high case fatality, and potential pandemic potential.
• Priority Actions: Identify sources, adapt surveillance, and prepare for future outbreaks.