Influenza Update N° 453

Overview

4 September 2023, based on data up to 20 August 2023

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)

• Countries are recommended to monitor the relative co-circulation of influenza and SARS-CoV-2 viruses in integrated surveillance and report to RespiMART (FluNet and FluID) directly or via regional platforms. Clinicians should consider influenza in differential diagnosis, especially for high-risk groups for influenza, and test and treat according to national and WHO guidance. 
• Globally, influenza detections remained low.
• In Oceania, influenza activity decreased with influenza A(H1N1)pdm09 and influenza B viruses predominant.
• In South Africa, influenza activity of predominately influenza A(H3N2) viruses remained below the seasonal threshold after peaking in early June.
• In temperate South America, influenza detections remained low overall with A and B viruses co-circulating. Severe acute respiratory infections (SARI) activity remained above seasonal baselines in Chile, Paraguay and Uruguay.
• In the Caribbean countries, influenza activity remained low overall.
• In the Central American countries, influenza activity decreased overall with influenza B viruses most frequently detected followed by A(H1N1)pdm09 viruses.
• overall influenza activity was low with detections of predominantly A(H1N1)pdm09 and B viruses. 
• In tropical Africa, influenza detections remained low overall and in most reporting countries, with influenza A(H1N1)pdm09 and A(H3N2) viruses predominantly detected.
• In Southern Asia, influenza activity remained low overall with increased detections reported in Bangladesh, Bhutan and Nepal.
• In South-East Asia, influenza activity remained elevated overall, with continued reporting of predominantly influenza A(H1N1)pdm09 and A(H3N2) virus detections.
• In the temperate zones of the northern hemisphere, indicators of influenza activity were reported at low levels or below seasonal threshold in most reporting countries. Detections were predominantly influenza A(H1N1)pdm09 followed by influenza B and influenza A(H3N2) viruses.
• National Influenza Centres (NICs) and other national influenza laboratories from 108 countries, areas or territories reported data to FluNet for the time period from 7 August 2023 to 20 August 2023 (data as of 31/08/2023 04:10:26 PM UTC). The WHO GISRS laboratories tested more than 230 916 specimens during that time period. 5040 were positive for influenza viruses, of which 3558 (70.6%) were typed as influenza A and 1482 (29.4%) as influenza B. Of the sub-typed influenza A viruses, 991 (38.0%) were influenza A(H1N1)pdm09 and 1617 (62.0%) were influenza A(H3N2). Of the type B viruses for which lineage was determined, all (560) belonged to the B/Victoria lineage.

• Globally, SARS-CoV-2 positivity from sentinel surveillance increased to just above 10%. Activity increased to just above 20% in the Eastern Mediterranean Region, to 14% in the Region of the Americas and to around 10% in the Western Pacific Region. Positivity decreased to around 20% in the European Region. Positivity remained below 10% in the African and South-East Asia Region. SARS-CoV-2 positivity from non-sentinel surveillance was just below 10% globally.
• From countries with RSV surveillance in place, RSV activity was generally low except in Western Australia and some countries in central America and temperate and tropical South America.
• 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. The guidance can be found here: https://covid.comesa.int/publications/i/item/WHO-2019-nCoV-integrated_sentinel_surveillance-2022.1.
• NICs and other national influenza laboratories from 70 countries, areas or territories from six WHO regions (African Region: 14; Region of the Americas: 20; Eastern Mediterranean Region: 2; European Region: 20; South-East Asia Region: 7; Western Pacific Region: 7) reported to FluNet from sentinel surveillance sites for time period from 7 August 2023 to 20 August 2023 (data as of 31/08/2023 04:10:26 PM UTC). The WHO GISRS laboratories tested more than 19 566 sentinel specimens during that time period and 1856 (9.49%) were positive for SARS-CoV-2. Additionally, more than 32 643 non-sentinel or undefined reporting source samples were tested in the same period and 2939 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.