Influenza Update N° 425

Overview

8 August 2022, based on data up to 24 July 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.
• Global influenza activity has steadily decreased from a peak in March 2022.
• In the temperate zones of the southern hemisphere, overall influenza activity appeared to decrease this reporting period.
• In Oceania, detections of primarily influenza A(H3N2) decreased overall, but elevated influenza-like activity (ILI) was reported in some Pacific Island countries.
• In Southern Africa, influenza activity decreased overall with continued detections of influenza A(H1N1)pdm09 and influenza A(H3N2) and a few influenza B viruses.
• In the Caribbean and Central American countries, low influenza activity was reported with influenza A(H3N2) predominant.
• In the tropical countries of South America, influenza detections were low, and A(H3N2) detections predominated.
• In tropical Africa, influenza activity continued to decrease. Influenza A viruses predominated among the reported detections.
• In Southern Asia, influenza detections of predominantly A(H3N2) were at similar levels to previous weeks and remained at low levels overall.
• In South-East Asia, influenza virus detections decreased. Influenza A(H3N2) predominated.
• In the countries of North America, influenza activity continued to decrease to levels typically observed at this time of year. Activity was predominantly due to influenza A viruses, with A(H3N2) predominant among the 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) seemed to have peaked. Elsewhere, influenza illness indicators and activity remained low.
• In Western Asia, low numbers of detections of influenza A(H1N1)pdm09, A(H3N2) and B viruses were reported.
• National Influenza Centres (NICs) and other national influenza laboratories from 120 countries, areas or territories reported data to FluNet for the time period from 11 July 2022 to 24 July 2022 (data as of 5/8/2022 7:23:00 AM UTC). The WHO GISRS laboratories tested more than 145 086 specimens during that time period. 6449 were positive for influenza viruses, of which 6 301 (97.7%) were typed as influenza A and 148 (2.3%) as influenza B. Of the subtyped influenza A viruses, 157 (2.7%) were influenza A(H1N1)pdm09 and 5640 (97.3%) were influenza A(H3N2). Of the characterised influenza B viruses, 44 (100%) belonged to the B-Victoria lineage and none belonged to the Yamagata 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 can be found here: https://covid.comesa.int/publications/i/item/WHO-2019-nCoV-integrated_sentinel_surveillance-2022.1.
• COVID-19 positivity from sentinel surveillance decreased a little over the reporting period and remained over 50%. An increase was observed in the Western Pacific Region, but activity in all other regions decreased or remained stable. Activity from non-sentinel sites remained stable overall, with overall positivity around 45%.
• National Influenza Centres (NICs) and other national influenza laboratories from 82 countries, areas or territories reported data to FluNet for the time period from six WHO regions (African Region: 15; Region of the Americas: 23; Eastern Mediterranean Region: 3; European Region: 30; South-East Asia Region: 7; Western Pacific Region: 4) reported to FluNet from sentinel surveillance sites for time period from 11 July 2022 to 24 July 2022 (data as of 5/8/2022 7:23:00 AM UTC). The WHO GISRS laboratories tested more than 101 931 sentinel specimens during that time period and 56 496 (55.4%) were positive for SARS-CoV-2. Additionally, 1 016 516 non-sentinel or undefined reporting source samples were tested in the same period and 458 136 (45.0%) 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.