2023-10-29-世界卫生组织-Influenza_Update_N°_457_12页_1mb

Influenza Update N° 457 Summary (30 October 2023)

Core Content Overview

This update provides an analysis of global influenza and SARS-CoV-2 surveillance data as of 15 October 2023, with additional insights into respiratory syncytial virus (RSV) activity where available. It highlights trends in influenza activity across different regions and emphasizes the importance of integrated surveillance for influenza and SARS-CoV-2.

Key Findings

Global Influenza Activity

• Overall trend: Influenza detections remained low globally, with most activity reported from tropical areas and increased activity in the temperate Northern hemisphere in parts of Eastern and Western Asia.
• Subtype distribution:
  • Influenza A: 83.0% of positive specimens, with A(H1N1)pdm09 (32.8%) and A(H3N2) (67.2%) as the main subtypes.
  • Influenza B: 17.02%, all belonging to the B/Victoria lineage.
• Regional activity:
  • Oceania: Influenza activity decreased, with A viruses predominant.
  • South Africa: Influenza activity remained below the seasonal threshold.
  • Temperate South America: Influenza detections were low and decreasing in most countries, but Chile reported an increase in B viruses.
  • Central America and Caribbean: Influenza activity increased to moderate levels in the Caribbean, with A(H1N1)pdm09 and B/Victoria predominant.
  • Tropical South America: Influenza activity was low and decreasing, with B viruses predominant.
  • Tropical Africa:
    • Western Africa: Influenza detections decreased overall, but A(H3N2) increased in Burkina Faso and Ghana.
    • Middle Africa: Low influenza activity, with A and B viruses reported in Cameroon, Gabon, and Central African Republic.
    • Eastern Africa: Low influenza activity, with B viruses predominant in Ethiopia, Mozambique, and Rwanda.
  • Southern Asia: Influenza activity remained low, but Iran reported increased detections, mainly A viruses.
  • South-East Asia: Influenza activity decreased, with A(H1N1)pdm09 and A(H3N2) predominant. Lao People's Democratic Republic and Thailand reported increased activity.
  • Northern Hemisphere (temperate):
    • North America: Low influenza activity, with A(H1N1)pdm09 predominant in the USA.
    • Europe: Low or below baseline activity in most countries, except Israel where it was moderate. A viruses were predominant.
    • Eastern Asia: Influenza activity increased, mainly in Japan, Republic of Korea, and Southern China, with A(H3N2) and A(H1N1)pdm09 predominant.
    • Western Asia: Increased influenza activity in the Arabic Peninsula, with A(H1N1)pdm09 and A(H3N2) detected. Some countries reported increased ILI activity.

SARS-CoV-2 Activity

• Sentinel surveillance:
  • Global positivity remained just below 10%, with below 5% in the African Region and South-East Asia.
  • Americas: Positivity decreased, with Chile reporting an increase.
  • Europe: Positivity increased in Belarus, Denmark, and Germany.
• Non-sentinel surveillance: Positivity increased to around 20% globally.

RSV Activity

• RSV activity was generally low or decreasing in most regions, except for central America, tropical South America, and parts of the European region and USA.
• Barbados, Dominican Republic, Panama, Colombia, and others reported increased RSV activity.

Recommendations and Guidance

• Integrated surveillance is encouraged for influenza and SARS-CoV-2, especially for countries that have received multiplex reagent kits from GISRS.
• Clinicians are advised to consider influenza in the differential diagnosis for high-risk groups and follow national and WHO guidelines for testing and treatment.
• Data reporting to FluNet and regional platforms should be timely and consistent to improve surveillance accuracy.

Data Sources and Reporting

• FluNet and FluID are used for influenza surveillance, with data reported by 124 countries.
• GISRS laboratories tested over 357,752 specimens, with 11,470 positive for influenza.
• Sentinel surveillance data from 85 countries were reported, including 2555 positive SARS-CoV-2 specimens from sentinel sites and 4944 from non-sentinel sources.
• Additional surveillance outputs and interface reports between influenza and SARS-CoV-2 are available through WHO regional offices and the FluNet dashboard.

Additional Information

• RSV maps and influenza subtype charts are provided for various regions, including Central America, Western Africa, Southern Asia, South-East Asia, and the Northern Hemisphere.
• The WHO Global Influenza Surveillance and Response System (GISRS) continues to monitor and report on influenza and other respiratory viruses.
• Data completeness may vary due to the availability and quality of information at the time of the update.

Contact

For more information or queries, contact: fluupdate@who.int.