Influenza Update N° 451

Overview

07 August 2023, based on data up to 23 July 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, with activity in many countries in the southern hemisphere now decreasing after having peaked in recent weeks.
• In Oceania, influenza activity decreased, with influenza A viruses predominant.
• In South Africa, influenza activity of predominately influenza A(H3N2) viruses decreased to below the seasonal threshold after peaking in early June.  
• In temperate South America, influenza detections continued to decrease with A(H1N1)pdm09 viruses most frequently detected followed by B viruses. Severe acute respiratory infections (SARI) activity declined in most countries.
• In the Caribbean countries, influenza activity remained low overall.
• In the Central American countries, influenza activity decreased overall with A(H1N1)pdm09 most frequently detected followed by B/Victoria lineage viruses.
• overall influenza activity was low with detections of predominantly A(H1N1)pdm09 and B viruses. 
• In tropical Africa, influenza detections remained low in reporting countries with influenza A(H1N1)pdm09 viruses predominantly detected.
• In Southern Asia, influenza activity remained low overall except in Bangladesh and the Maldives where detections were elevated.
• In South-East Asia, influenza activity remained stable in most reporting countries, with continued reporting of predominantly A(H1N1)pdm09 and A(H3N2) virus detections.
• In the temperate zones of the northern hemisphere, influenza activity was 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.
• Globally, RSV activity was generally low except in some parts of Australia and some countries in tropical and central South America.
• National Influenza Centres (NICs) and other national influenza laboratories from 106 countries, areas or territories reported data to FluNet for the time period from 10 July 2023 to 23 July 2023* (data as of 04/08/2023 07:07:00AM UTC). The WHO GISRS laboratories tested more than 215 359 specimens during that time period. 5532 were positive for influenza viruses, of which 3999 (72.29%) were typed as influenza A and 1533 (27.71%) as influenza B. Of the sub-typed influenza A viruses, 1346 (51.16%) were influenza A(H1N1)pdm09 and 1285 (48.84%) were influenza A(H3N2). Of the type B viruses for which lineage was determined, all (508) belonged to the B/Victoria lineage.  

• Globally, SARS-CoV-2 positivity from sentinel surveillance decreased to below 10%. Activity decreased slightly to just below 10% in the Eastern Mediterranean Region and the European Region and was stable or decreasing elsewhere. Activity was highest in the Western Pacific Region at around 12%, followed by the Region of the Americas at around 10%, with all other regions reporting below 10% positivity. SARS-CoV-2 positivity from non-sentinel surveillance was reported around 10% globally. 
• 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.
• National Influenza Centres (NICs) and other national influenza laboratories from 71 countries, areas or territories from six WHO regions (African Region: 13; Region of the Americas: 21; Eastern Mediterranean Region: 2; European Region: 24; South-East Asia Region: 5; Western Pacific Region: 6) reported to FluNet from sentinel surveillance sites for time period from 10 July 2023 to 23 July 2023* (data as of 04/08/2023 07:07:00 AM UTC). The WHO GISRS laboratories tested more than 23629 sentinel specimens during that time period and 1906 (8.07%) were positive for SARS-CoV-2. Additionally, more than 42625 non-sentinel or undefined reporting source samples were tested in the same period and 4094 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.