2022-12-22-世界卫生组织-Influenza_Update_N°_435_12页_1mb

Influenza Update N° 435 Summary (23 December 2022)

Core Content

This Influenza Update provides a global overview of influenza activity and SARS-CoV-2 surveillance data, based on reports up to 11 December 2022. It emphasizes the importance of monitoring co-circulation of influenza and SARS-CoV-2 viruses, especially in the context of the ongoing pandemic, and highlights the need for integrated surveillance and timely reporting.

Main Points

• Integrated Surveillance: Countries are encouraged to monitor both influenza and SARS-CoV-2 simultaneously, particularly those that have received multiplex reagent kits from GISRS.
• Vaccination Campaigns: Northern hemisphere countries are advised to step up influenza vaccination efforts to prevent severe disease and hospitalizations.
• Differential Diagnosis: Clinicians should consider influenza in the differential diagnosis for high-risk groups and follow national guidelines for testing and treatment.
• Data Interpretation: Due to changes in surveillance during the pandemic, comparisons with previous seasons may not be valid, and data should be interpreted cautiously.

Key Information by Region

Global Overview

• Influenza activity remained elevated globally, primarily due to northern hemisphere activity.
• Influenza A(H3N2) viruses were predominant in most regions.
• SARS-CoV-2 positivity from sentinel surveillance increased in the Americas and Western Pacific, while it decreased in other regions.
• Globally, 81,619 influenza specimens were positive, with 97% being influenza A and 3% influenza B.
• Influenza A(H3N2) accounted for 71.4% of subtyped A viruses, while A(H1N1)pdm09 accounted for 28.6%.

Northern Hemisphere

• North America:
  • Influenza activity remained high.
  • ILI increased in Canada above the pre-pandemic average.
  • Influenza A(H3N2) dominated, with A(H1N1)pdm09 at 5% in Canada and 20% in the USA.
  • RSV activity remained elevated in Canada and peaked in both countries.
• Europe:
  • Influenza activity continued to rise, with positivity from sentinel sites at 23%, above the epidemic threshold.
  • Influenza A(H3N2) was predominant in sentinel sites, while A(H1N1)pdm09 was more common in non-sentinel sites.
  • 17 countries reported SARI cases, with 21% of tested specimens positive for influenza, higher than SARS-CoV-2.
• Central Asia:
  • Influenza activity increased, with A(H1N1)pdm09 and B viruses reported in most countries.
  • ILI increased in Kazakhstan, Kyrgyzstan, and Uzbekistan.
  • SARI was elevated in Kyrgyzstan.
• Northern Africa:
  • Influenza detections increased but remained low.
  • Morocco reported mainly B/Victoria lineage.
  • Tunisia reported increasing detections of A(H1N1)pdm09 and some A(H3N2) and B/Victoria.
• Western Asia:
  • Influenza activity decreased in most countries of the Arabian Peninsula.
  • Qatar reported a slight increase in all subtypes.
  • Georgia saw a steep increase in A(H3N2) activity.
• East Asia:
  • Influenza activity remained low overall.
  • Southern China and the Republic of Korea reported slight increases.
  • RSV activity continued to decline in the Republic of Korea.
• Caribbean and Central America:
  • Influenza activity decreased, with A(H3N2) predominant.
  • Mexico reported elevated activity, while RSV activity remained low.
• South America (Tropical):
  • Influenza detections remained low, with A(H3N2) predominant.
  • SARI was elevated in some countries like Colombia, Ecuador, and Suriname.
  • RSV activity continued to decline in most areas, except Brazil.

Southern Hemisphere (Temperate Zones)

• Oceania:
  • Influenza activity remained low in Australia.
  • RSV activity decreased in Australia and remained stable in New Zealand.
• South Africa:
  • Influenza detection rates remained below the epidemic threshold.
  • RSV detection rates in children under five increased slightly.
• Temperate South America:
  • Influenza activity decreased across the subregion.
  • Argentina and Chile reported moderate levels of positivity.
  • Influenza B was predominant in Argentina, while A(H3N2) was predominant in Chile.
  • SARI was above the epidemic threshold in Paraguay and Uruguay.
  • RSV remained low in the subregion.

Tropical Zones

• Tropical Africa:
  • Influenza activity remained low overall.
  • Eastern Africa reported increased detections, with a mix of A(H1N1)pdm09, A(H3N2), and B viruses.
  • Influenza epidemics driven by A(H1N1)pdm09 were reported in French territories.
• Tropical Asia:
  • Southern Asia saw a decrease in influenza activity, mainly due to reduced activity in Iran.
  • Influenza A(H1N1)pdm09 was predominant in Afghanistan, Pakistan, and Sri Lanka.
  • Influenza B/Victoria lineage viruses were predominant in Cambodia and Lao PDR.
  • Influenza A(H3N2) was predominant in Singapore and Thailand.
  • In South-East Asia, influenza B remained elevated in Malaysia.

Additional Notes

• SARS-CoV-2 Sentinel Surveillance:
  • SARS-CoV-2 positivity from sentinel surveillance increased in the Americas and Western Pacific.
  • SARS-CoV-2 positivity was lower in other regions.
  • SARS-CoV-2 data are reported from a limited number of countries, and trends may not reflect the entire region.
• Data Sources:
  • FluNet and GISRS provide data from 130 countries for influenza.
  • SARS-CoV-2 data are collected from sentinel surveillance sites.
  • Data completeness may vary due to availability and quality.

Conclusion

The update underscores the ongoing need for vigilance in influenza surveillance, especially in the context of co-circulating SARS-CoV-2. It highlights the regional variations in influenza activity, with the northern hemisphere still experiencing elevated levels, and emphasizes the importance of integrated surveillance and vaccination efforts.