Influenza Update N° 419

16 May 2022
 | Emergency situation update
Influenza Update N° 419
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Overview

16 May 2022, based on data up to 1 May 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. 
  • Globally, influenza activity continued to decrease, following a peak in March 2022.
  • Countries are recommended to monitor for 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.
  • In the temperate zones of the northern hemisphere, influenza activity decreased or remained stable. Detections were mainly influenza A(H3N2) viruses and B/Victoria lineage viruses, with some detections of A(H1N1)pdm09 viruses.
  • In the countries of North America, influenza activity was stable compared to the previous period and influenza positivity was higher than usual for this time of year and was predominantly due to influenza A viruses, with A(H3N2) predominant among the subtyped viruses. Respiratory syncytial virus (RSV) activity remained low in the United States of America (USA) and Canada. 
  • In Central Asia, a single influenza B detection was reported in Kazakhstan.
  • In Europe, overall influenza continues to decline with influenza A(H3N2) predominant. 
  • In East Asia, in China influenza activity with mainly influenza B/Victoria lineage detections continued to decrease, with A(H3N2) becoming the predominantly detected virus across the southern provinces. Elsewhere, influenza illness indicators and activity remained low. 
  • In Northern Africa, Tunisia continued to report few detections of mainly influenza A(H3N2) and one influenza A(H1N1)pdm09 detection, and Egypt reported increasing detections of influenza B followed by A(H3N2).
  • In Western Asia, influenza activity was low across reporting countries, with the exception of Georgia where detections of influenza A(H3N2) continued to be reported though decreasing.
  • In the Caribbean and Central American countries, low influenza activity was reported with influenza A(H3N2) predominant.
  • In tropical South America, low influenza activity was reported with influenza A(H3N2) predominant.
  • In tropical Africa, influenza activity remained low with influenza A(H3N2) predominating followed by influenza B/Victoria lineage viruses.
  • In Southern Asia, influenza virus detections were at low levels with a few detections of A(H3N2) and A(H1N1)pdm09 viruses. 
  • In South-East Asia, low detections of A(H3N2) were reported in Singapore and Timor-Leste.
  • In the temperate zones of the southern hemisphere, influenza activity was low overall as expected at this time of year, except in Argentina and Chile. In Argentina, influenza detections remained elevated, and positivity was at a high intensity level. In Chile, positivity increased above the epidemic threshold.
  • National Influenza Centres (NICs) and other national influenza laboratories from 111 countries, areas or territories reported data to FluNet for the time period from 18 April 2022 to 01 May 2022* (data as of 2022-05-13 06:58:26 UTC). The WHO GISRS laboratories tested more than 346 542 specimens during that time period. 27 625 were positive for influenza viruses, of which 27 081 (98%) were typed as influenza A and 544 (2%) as influenza B. Of the sub-typed influenza A viruses, 283 (6.5%) were influenza A(H1N1)pdm09 and 4098 (93.5%) were influenza A(H3N2). Of the characterized B viruses, all 257 (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.

  • Overall COVID positivity from sentinel surveillance increased during the reporting period and was just above 10%. The highest increases were observed in the Western Pacific Region of WHO, with positivity at 28%. A significant increase was also observed the South-East Asian Region of WHO with positivity at 16%. Activity from non-sentinel sites was varied. Similar to sentinel sites, the largest increase in positivity was observed in the Western Pacific Region of WHO where positivity was above 30%. Activity also increased in the African and Eastern Mediterranean Regions of WHO, but remained under 10%. Activity decreased among non-sentinel sites in the Region of the Americas of WHO, but similar to the region’s sentinel sites, positivity remained under 10%. Activity also decreased significantly among South-East Asia Region of WHO, but remained elevated above 30%.
  • NICs and other national influenza laboratories from 46 countries, areas or territories from six WHO regions (African Region: 1; Region of the Americas: 15; Eastern Mediterranean Region: 3; European Region: 20; South-East Asia Region: 4; Western Pacific Region: 3) reported to FluNet from sentinel surveillance sites for time period from 18 Apr 2022 to 01 May 2022 (data as of 2022-05-13 06:58:26 UTC). The WHO GISRS laboratories tested more than 30 065 sentinel specimens during that time period and 2741 (9.1%) were positive for SARS-CoV-2. Additionally, more than 496 585 non-sentinel or undefined reporting source samples were tested in the same period and 31 982 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)