Influenza Update N° 428

19 September 2022
 | Emergency situation update
Influenza Update N° 428
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Overview

19 September 2022, based on data up to 4 September 2022

Information in this report is categorized by influenza transmission zones, which are geographical groups of countries, areas or territories with similar influenza transmission patterns. For more information on influenza transmission zones, see the link below:

Influenza Transmission Zones (pdf, 659kb)

  • The current influenza surveillance data should be interpreted with caution as the ongoing COVID-19 pandemic has influenced to varying extents health seeking behaviours, staffing/routines in sentinel sites, as well as testing priorities and capacities in Member States. Various hygiene and physical distancing measures implemented by Member States to reduce SARS-CoV-2 virus transmission have likely played a role in reducing influenza virus transmission. 
  • Countries are recommended to monitor the co-circulation of influenza and SARS-CoV-2 viruses. They are encouraged to enhance integrated surveillance and step-up their influenza vaccination campaign to prevent severe disease and hospitalizations associated with influenza. Clinicians should consider influenza in differential diagnosis, especially for high-risk groups for influenza, and test and treat according to national guidance.
  • Globally, influenza activity remained low. Generally, activity has decreased or remained low in most countries this period
  • In the temperate zones of the southern hemisphere, overall influenza activity appeared to further decrease this reporting period, except in South Africa where activity increased.
  • In Oceania, detections of primarily influenza A(H3N2) decreased overall and influenza-like activity (ILI) activity was at low levels in most Pacific Island countries.
  • In Southern Africa, there was an increase in influenza activity again in recent weeks with mainly influenza B viruses reported.
  • In the Caribbean and Central American countries, low influenza activity was reported with influenza A(H3N2) most frequently detected.
  • In the tropical countries of South America, influenza detections were low and A(H3N2) detections predominated.
  • In tropical Africa, influenza activity remained low with influenza A(H3N2) viruses predominant among the reported detections.
  • In Southern Asia, influenza detections were predominantly A(H1N1)pdm09 viruses, with influenza A(H3N2) and influenza B viruses also reported.
  • In South-East Asia, influenza activity decreased a little, with influenza A(H3N2) viruses predominant.
  • In the countries of North America, influenza activity remained at inter-seasonal levels as typically observed at this time of year. Influenza A(H3N2) was predominant among the few subtyped viruses.
  • In Europe, overall influenza activity remained at inter-seasonal levels with influenza A(H3N2) predominant among the subtyped viruses.
  • In Central Asia, no influenza detections were reported.
  • In Northern Africa, no influenza detections were reported.
  • In East Asia, influenza activity of predominantly influenza A(H3N2) continued to decrease in China. Elsewhere, influenza illness indicators and activity were low.
  • In Western Asia, detections of predominantly influenza A(H3N2) and B viruses continued to be reported, through at low levels.
  • National Influenza Centres (NICs) and other national influenza laboratories from 102 countries, areas or territories reported data to FluNet for the time period from 22 August 2022 to 04 September 2022* (data as of 2022-09-16 04:55:15 UTC).The WHO GISRS laboratories tested more than 112 017 specimens during that time period. 3879 were positive for influenza viruses, of which 3585 (92.4%) were typed as influenza A and 294 (7.6%) as influenza B. Of the sub-typed influenza A viruses, 361 (12.3%) were influenza A(H1N1)pdm09 and 2578 (87.7%) were influenza A(H3N2). Of the characterized B viruses, 131 (100%) belonged to the B/Victoria lineage.

During the COVID-19 pandemic, WHO encourages countries, especially those that have received the multiplex influenza and SARS-CoV-2 reagent kits from GISRS, to conduct integrated surveillance of influenza and SARS-CoV-2 and report epidemiological and laboratory information in a timely manner to established regional and global platforms. Revised interim guidance has just been published here: https://covid.comesa.int/publications/i/item/WHO-2019-nCoV-integrated_sentinel_surveillance-2022.1.

  • COVID-19 positivity from sentinel surveillance continued to decrease to just over 10%. The highest positivity rates were reported in the Region of the Americas, the European Region and the Eastern Mediterranean Region, where positivity was just above 10%, while in the other regions it remained below 5%. The positivity rate decreased in most regions and most notably in the Western Pacific Region, except in the African and European Regions, where it was stable. 
  • National Influenza Centres (NICs) and other national influenza laboratories from 49 countries, areas or territories from six WHO regions (African Region: 11;  Region of the Americas: 13;  Eastern Mediterranean Region: 3;  European Region: 17;  South-East Asia Region: 3;  Western Pacific Region: 2) reported data from sentinel surveillance sites to FluNet for the  time period from 22 Aug 2022 to 04 Sep 2022* (data as of 2022-09-16 04:55:15  UTC). The WHO GISRS laboratories tested more than 46 526 sentinel specimens during that time period and 3399 (14.2%) were positive for SARS-CoV-2. Additionally, more than 196 373 non-sentinel or undefined reporting source samples were tested in the same period and 2 5625 were positive for SARS-CoV-2. Further details are included at the end of this update.

Source of data

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The Global Influenza Programme monitors influenza activity worldwide and publishes an update every two weeks. The updates are based on available epidemiological and virological data sources, including FluNet (reported by the WHO Global Influenza Surveillance and Response System), FluID (epidemiological data reported by national focal points) and influenza reports from WHO Regional Offices and Member States. Completeness can vary among updates due to availability and quality of data available at the time when the update is developed.

*It includes data only from countries reporting on positive and negative influenza specimens.

 

WHO Team
Global Influenza Programme (GIP)