2021-12-06-世界卫生组织-Weekly_epidemiological_update_on_COVID-19_-_7_December_2021_19页_2mb

COVID-19 Weekly Epidemiological Update (Edition 69) Summary

Global Outbreak Overview

• Week 49: As of Dec 5, 2021, weekly cases stabilized (4.2 million new cases), matching prior week, but deaths increased by 10% (Over 52,500 new deaths).
• Cumulative Totals: ≈265.9 million cases and ≈5.2 million deaths globally.
• Regional Variations:
  • Americas (+21%), Africa (+79%), Europe (≈2%), SE Asia (-10%), Western Pacific (-10%), EMRO (-8%).
  • Case Rate per 100k: European & Americas the highest.
  • Death Rate per 100k: European & Americas the highest.

Special Focus: Variants

WHO's Assessment Process

• Continuously assess variants for transmissibility, disease characteristics, or efficacy impact on vaccines/therapeutics/diagnostics/PHSMs.
• Designations (VOC/VOI/VUM) are dynamic based on epidemiology and emerging evidence.

Geographic Spread of Variants

• Dominant variant before Omicron: Delta.
• Slowly declining Alpha/Beta/Gamma proportions.
• Omicron confirmed in 57 WHO regions, initially reported mostly via travel clusters.

Variant of Concern Update: Omicron (B.1.1.529)

Background & Characteristics

• First Reported: Nov 9, 2021 (South Africa), designated VOC Nov 26 due to its numerous mutations (≈30 in spike protein) and immune escape concerns.

Epidemiology

• • South Africa:
  • Case incidence surged by 111% within the two weeks after Omicron emergence.
  • High transmissibility observed, exacerbated by lower vaccination rates (25.2% fully vaccinated) and post-designation testing surge.
  • ↑ Hospital admissions by 82% (502→912) – preliminary, proportional to Omicron cases unknown.
• • Neighboring Countries: Eswatini, Zimbabwe, Mozambique, Namibia, Lesotho saw massive jumps (>200%).
• • Global Presence: Confirmed in 57 countries, still too early to assess global impact.

Transmissibility

• Likely >growth advantage (forecasted for Europe).
• Early estimates constrained by limited data.

Clinical Severity & Immune Escape

• Clinical Data:
  • Cases from EU (~200): mostly asymptomatic/mild.
  • South Africa saw severe case surge.
  • With potential effective immunity lower than Delta, higher case loads likely = higher hospitalizations, temporary lags for deaths may occur.
• Re-infection Risk:
  • Preliminary: Increased risk noted in South Africa (Relative Hazard Ratio ≈2.39 vs historical periods).
  • Delta vaccines not adequate, Omicron escape more extensive – need more detailed studies.

Diagnostics Impact

• PCR tests with multi-gene targets should still detect Omicron.
• SGTF (S-gene target failure): Initial marker for Omicron, but occurs also in Alpha subsets/Gamma/Delta.
• No impact reported on WHO-approved Ag-RDTs.

Treatment Impact

• Treatments targeting inflammation (IL-6 blockers, corticosteroids) remain effective.

WHO Recommendations

• Countries should accelerate vaccine access, strengthen surveillance, report variant data, protect themselves via ventilation, masks, hand hygiene.

WHO Regional Overview (Dec 2-5 Data)

• Americas: substantial increase in cases (+21%) from the US (227.3/100k), large increases from Brazil and others. Deaths also ↑38%.
• Africa: High increases (79% cases) mostly from SA/Others (Eswatini etc, very low vac cov).
• EMRO: medium case increases from Jordan/Iran/Lebanon. Deaths ↓8% less than previous week.
• Europe: Cases plateaued (265/100k) stable with high US/Europe cases; deaths 29k stable.
• SE Asia/Western Pacific: Overall declines, subnational variations. High case increases only seen regionally.

Operational Updates Highlights

• Global efforts noted: Kenya vaccination equity, oxygen stations in Yemen, emergency response mgmt in Africa.

Additional Resources & References

• WHO variant tracking, dashboard, clinical data platform.