Influenza Update N° 416

Overview

04 April 2022, based on data up to 20 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 in comparison with pre-COVID years, but activity has increased again since February 2022 after an initial decrease in January 2022.
• 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 continues to increase with influenza A(H3N2) predominant. Very little RSV activity was observed.
• In Central Asia, no influenza detections were reported.
• In East Asia, influenza activity with mainly influenza B/Victoria lineage detections appeared to decrease in China. Elsewhere, influenza illness indicators and activity remained low. Increased RSV activity was reported in Mongolia.
• In Northern Africa, influenza detections of influenza A(H3N2) continued to be reported in Tunisia. 
• In Western Asia, influenza activity was low across reporting countries.
• 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 was reported mainly 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  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 viruses (with A(H3N2) predominant among the subtyped viruses) continued to be reported in some countries in temperate South America and South Africa.
• National Influenza Centres (NICs) and other national influenza laboratories from 111 countries, areas or territories reported data to FluNet for the time period from 07 March 2022 to 20 March 2022* (data as of 2022-04-01 06:58:55 UTC). The WHO GISRS laboratories tested more than 377 735 specimens during that time period. 32 703 were positive for influenza viruses, of which 29 030 (88.8%) were typed as influenza A and 3673 (11.2%) as influenza B. Of the sub-typed influenza A viruses, 315 (6.5%) were influenza A(H1N1)pdm09 and 4504 (93.5%) were influenza A(H3N2). Of the characterized B viruses, none belonged to the B-Yamagata lineage and 3440 (100%) 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://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 to around 10% in all WHO regions during this reporting period except in the Eastern Mediterranean Region where activity increased slightly to 18% and in the European Region where activity was stable around 15%. 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: 15;  Eastern Mediterranean Region: 4;  European Region: 28;  South-East Asia Region: 3;  Western Pacific Region: 4 ) reported to FluNet from sentinel surveillance sites for time period from 07 Mar 2022 to 20 Mar 2022* (data as of 2022-04-01 06:58:55 UTC). The WHO GISRS laboratories tested more than 38 168 sentinel specimens during that time period and 4808 (12.6%) were positive for SARS-CoV-2. Additionally, more than 982 044 non-sentinel or undefined reporting source samples were tested in the same period and 66 425 were positive for SARS-CoV-2. Further details are included at the end of this update and in the surveillance outputs here.

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.