Influenza Update N° 415

Overview

21 March 2022, based on data up to 06 March 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 remained low and decreased this period after a peak at the end of 2021.
• With the increasing detections of influenza during COVID-19 pandemic, countries are recommended to prepare for co-circulation of influenza and SARS-CoV-2 viruses. They are encouraged to enhance integrated surveillance to monitor influenza and SARS-CoV-2 at the same time, 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 increased or remained stable with detections of mainly influenza A(H3N2) viruses and B/Victoria lineage viruses reported.
• In North America, influenza activity increased in recent weeks but remained lower than pre-COVID-19 pandemic levels at this time of the year and was predominantly due to influenza A viruses, with A(H3N2) predominant among the subtyped viruses. Respiratory syncytial virus (RSV) activity further decreased in the United States of America (USA) and Canada.
• In Europe, overall influenza activity appeared to increase again with influenza A(H3N2) predominant. Very little RSV activity was observed.
• In East Asia, influenza activity with mainly influenza B/Victoria lineage detections increased in China. Elsewhere, influenza illness indicators and activity remained low. Increased RSV activity was reported in Mongolia and the Republic of Korea.
• In Northern Africa, influenza detections of influenza A(H3N2) continued to be reported. 
• In Western Asia, influenza activity was low across reporting countries.
• In the Caribbean and Central American countries, influenza detections were predominantly influenza A(H3N2) and activity remained low.
• In tropical South America, low influenza activity was reported with influenza A(H3N2) predominant.
• In tropical Africa, influenza activity was reported from Eastern Africa with influenza A(H3N2) predominating followed by influenza B/Victoria lineage viruses.
• In Southern Asia, influenza virus detections were at low levels with influenza A(H1N1)pdm09, A(H3N2) and B viruses detected.
• In South-East Asia, influenza detections were at low levels with influenza A(H3N2) predominant.
• In the temperate zones of the southern hemisphere, influenza activity remained low overall, although detections of influenza A(H3N2) continude to be reported in some countries in temperate South America.
• National Influenza Centres (NICs) and other national influenza laboratories from 117 countries, areas or territories reported data to FluNet for the time period from 21 February 2022 to 06 March 2022* (data as of 2022-03-18 09:25:53 UTC).The WHO GISRS laboratories tested more than 367 148 specimens during that time period. 17 423 were positive for influenza viruses, of which 12 922 (74.2%) were typed as influenza A and 4501 (25.8%) as influenza B. Of the sub-typed influenza A viruses, 337 (12%) were influenza A(H1N1)pdm09 and 2475 (88%) were influenza A(H3N2). Of the characterized B viruses, none belonged to the B-Yamagata lineage and all (4371) belonged to the B-Victoria lineage.
• The WHO Consultation and Information Meeting on the Composition of Influenza Virus Vaccines for Use in the 2022-2023 Northern Hemisphere Influenza Season was held on 21-24 February 2022 in Geneva, Switzerland. The recommended composition of influenza virus vaccines for use in the 2022-2023 northern hemisphere influenza season can be consulted at the following link: https://www.who.int/publications/m/item/recommended-composition-of-influenza-virus-vaccines-for-use-in-the-2022-2023-northern-hemisphere-influenza-season.

• 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://www.who.int/publications/i/item/WHO-2019-nCoV-integrated_sentinel_surveillance-2022.1.
• At the global level, SARS-CoV-2 percent positivity from sentinel surveillance decreased across all WHO regions during this reporting period except in the South-East Asia Region where the positivity was above 40%. The positivity rate was between 10% and 30% in all Regions of WHO, with exception of the African Region of WHO where positivity remained under 10%. Overall positivity from non-sentinel sites also showed a decreasing trend.
• National Influenza Centres (NICs) and other national influenza laboratories from 55 countries, areas or territories reported data to FluNet for the time period from six WHO regions (African Region: 1;  Region of the Americas: 16;  Eastern Mediterranean Region: 4;  European Region: 26;  South-East Asia Region: 5;  Western Pacific Region: 3 ) reported to FluNet from sentinel surveillance sites for time period from 21 Feb 2022 to 06 Mar 2022* (data as of 2022-03-18 09:25:53 UTC). The WHO GISRS laboratories tested more than 54 328 sentinel specimens during that time period and 10 238 (18.8%) were positive for SARS-CoV-2. Additionally, more than 735 845 non-sentinel or undefined reporting source samples were tested in the same period and 112 402 were positive for SARS-CoV-2. Further details are included at the end of this update and in the surveillance outputs here 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.