Influenza Update N° 456

Overview

16 October 2023, based on data up to 1 October 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 most activity reported from tropical areas and increased activity reported in the temperate Northern hemisphere in Western and Eastern Asia.
• In Oceania, influenza activity decreased with influenza A viruses predominant.
• In South Africa, influenza activity remained below the seasonal threshold.
• In temperate South America, influenza detections remained low overall with A and B viruses co-circulating.
• In the Central American and Caribbean countries, influenza activity remained low overall.
• was low with detections of predominantly influenza B viruses. 
• In tropical Africa, all seasonal influenza subtypes co-circulated. Influenza detections remained low in Middle and Eastern Africa and decreased overall in Western Africa but remained elevated.
• In Southern Asia, influenza activity increased overall in the region and in some countries, except in Bangladesh where activity decreased.
• In South-East Asia, influenza activity remained elevated overall, with continued reporting of predominantly influenza A(H1N1)pdm09 and A(H3N2) virus detections. Some countries reported increasing influenza detections while other reported continued elevated activity.
• 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. But increased influenza activity was reported in parts of Eastern and Western Asia. Detections were predominantly influenza A(H3N2) followed by influenza A(H1N1)pdm09 and B viruses.
• National Influenza Centres (NICs) and other national influenza laboratories from 118 countries, areas or territories reported data to FluNet for the period from 18 September 2023 to 01 October 2023* (data as of 13/10/2023 06:08:28 AM UTC). The WHO GISRS laboratories tested more than 336 169 specimens during that period. 10 167 were positive for influenza viruses, of which 8316 (81.8%) were typed as influenza A and 1851 (18.2%) as influenza B. Of the sub-typed influenza A viruses, 1975 (31.2%) were influenza A(H1N1)pdm09 and 4355 (68.8%) were influenza A(H3N2). Of the type B viruses for which lineage was determined, all (854) belonged to the B/Victoria lineage. 

• Globally, SARS-CoV-2 positivity from sentinel surveillance remained around 10%. Activity decreased in the Region of the Americas to under 10% and decreased in the European Region to around 13%. Positivity remained below 10% in the other regions but with slight increases evident in the South-East Asia and Western Pacific Regions. SARS-CoV-2 positivity from non-sentinel surveillance remained around 14% globally. 
• From countries with RSV surveillance in place, RSV activity was generally low or decreasing except in some countries in central America and tropical South America. Early signs of RSV activity were noted in parts of the European region.
• 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 77 countries, areas or territories from six WHO regions (African Region: 16; Region of the Americas: 20; Eastern Mediterranean Region: 4; European Region: 27; South-East Asia Region: 4; Western Pacific Region: 6) reported to FluNet from sentinel surveillance sites for time period from 18 September 2023 to 01 October 2023* (data as of 13/10/2023 06:08:28 AM UTC). The WHO GISRS laboratories tested more than 33 367 sentinel specimens during that period and 2986 (9.0%) were positive for SARS-CoV-2. Additionally, more than 36 565 non-sentinel or undefined reporting source samples were tested in the same period and 5257 were positive for SARS-CoV-2. Further details are included at the end of this update.

Source of data
______________________________________________________________________________________________

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.