Influenza Update N° 450

Overview

24 July 2023, based on data up to 09 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, but in the southern hemisphere, some countries reported increased influenza detections in recent weeks while detections in other countries seemed to have peaked.
• In Oceania, influenza activity continued to increase with influenza A viruses predominant.
• In South Africa, influenza activity of predominately influenza A(H3N2) viruses continued to decrease 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 across all countries. Severe acute respiratory infections (SARI) activity remained elevated in a few 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 for Bangladesh and Iran (Islamic Republic of) were detections increased in recent weeks.
• 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 overall.
• 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 A (H3N2) and B viruses.
• Globally, RSV activity was generally low except in some part of Australia and some countries in tropical and central South America, and American Samoa.
• National Influenza Centres (NICs) and other national influenza laboratories from 107 countries, areas or territories reported data to FluNet for the time period from 26 June 2023 to 09 July 2023* (data as of 21/07/2023 07:32:59 AM UTC). The WHO GISRS laboratories tested more than 240 286 specimens during that time period. 5813 were positive for influenza viruses, of which 3984 (68.54%) were typed as influenza A and 1829 (31.46%) as influenza B. Of the sub-typed influenza A viruses, 1565 (66.20%) were influenza A(H1N1)pdm09 and 799 (33.80%) were influenza A(H3N2). Of the type B viruses for which lineage was determined, all (444) belonged to the B/Victoria lineage. 

• Globally, SARS-CoV-2 positivity from sentinel surveillance decreased to 11%. Activity increased slightly to around 16% in the Region of the Americas and continued to decrease to approximately 12% in the Western Pacific region. Activity was below 10% in the other regions. SARS-CoV-2 positivity from non-sentinel surveillance was reported around 16% 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 74 countries, areas or territories from six WHO regions (African Region: 14; Region of the Americas: 21; Eastern Mediterranean Region: 3; European Region: 24; South-East Asia Region: 5; Western Pacific Region: 7 )  reported to FluNet from sentinel surveillance sites for time period from 26 June 2023 to 09 July 2023* (data as of 21/07/2023 07:32:59 AM UTC). The WHO GISRS laboratories tested more than 29908 sentinel specimens during that time period and 3253 (10.88%) were positive for SARS-CoV-2. Additionally, more than 50431 non-sentinel or undefined reporting source samples were tested in the same period and 7648 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.