Influenza Update N° 449

Overview

10 July 2023, based on data up to 25 June 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)

• 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 was stable with influenza A viruses predominant.
• In South Africa, influenza activity appears to have peaked and decreased to a low level in pneumonia surveillance and below baseline in influenza-like illness (ILI) surveillance with influenza A(H3N2) viruses predominately detected.
• In temperate South America, influenza detections appeared to decrease to low levels 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, increased influenza activity was reported in a few countries with A(H1N1)pdm09 most frequently detected followed by B/Victoria lineage viruses.
• In the tropical countries of South America, overall influenza activity was low with detections of predominantly A(H1N1)pdm09 and B viruses. 
• In tropical Africa, influenza detections were low in reporting countries. Influenza A(H1N1)pdm09 viruses predominated among reported detections.
• In Southern Asia, influenza activity remained low with all seasonal subtypes detected.
• In South-East Asia, influenza activity remained stable or decreased 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 and B viruses.
• Globally, RSV activity was generally low except in Australia and some countries in tropical and temperate South America.
• National Influenza Centres (NICs) and other national influenza laboratories from 107 countries, areas or territories reported data to FluNet for the time period from 12 June 2023 to 25 June 2023 (data as of 07/07/2023 07:03:51 AM UTC). The WHO GISRS laboratories tested more than 265 159 specimens during that time period. 6147 were positive for influenza viruses, of which 4142 (67.4%) were typed as influenza A and 2005 (32.6%) as influenza B. Of the sub-typed influenza A viruses, 1768 (74.3%) were influenza A(H1N1)pdm09 and 611 (25.7%) were influenza A(H3N2). Of the type B viruses for which lineage was determined, all (458) belonged to the B/Victoria lineage.

• Globally, SARS-CoV-2 positivity from sentinel surveillance decreased to 13%. Activity decreased to approximately 15% in the Western Pacific region and remained around 13% in the Region of the Americas. Activity was around or 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.
• NICs and other national influenza laboratories from 70 countries, areas or territories from six WHO regions (African Region: 11; Region of the Americas: 20; Eastern Mediterranean Region: 2; European Region: 25; South-East Asia Region: 5; Western Pacific Region: 7) reported to FluNet from sentinel surveillance for time period from 12 June 2023 to 25 June 2023 (data as of 07/07/2023 07:03:51 AM UTC). The WHO GISRS laboratories tested more than 31 547 sentinel specimens during that time period and 4023 (12.8%) were positive for SARS‑CoV-2. Additionally, more than 58 826 non-sentinel or undefined reporting source samples were tested in the same period and 8115 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.