Influenza Update N° 466

Overview

4 March 2024, based on data up to 18 February 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 activity remained elevated in most northern hemisphere countries, although globally, influenza virus detections decreased. Influenza A viruses remain predominant globally.
• In the countries of North America, influenza activity remained within or below expected levels for this time of year in Canada and remained elevated but may have peaked in the United States of America (USA), with some indicators showing decreases. Influenza A(H1N1)pdm09 viruses predominated.
• In Europe and Central Asia, influenza activity decreased but remained elevated. Of 40 reporting countries, influenza activity was reported at very high intensity in two, high intensity in four, medium intensity in 19, low intensity in 13 and below baseline in two, and geographic spread was widespread in majority of reporting countries. Influenza hospitalizations and intensive care unit (ICU) admissions decreased but remained elevated. Influenza A virus detections predominated among detections in primary and secondary care sentinel surveillance, with A(H1N1)pdm09 viruses predominant.
• In Northern Africa, influenza detections decreased with detections of all seasonal influenza subtypes reported.
• In Eastern Asia, influenza activity continued to decrease overall.
• In Western Asia, influenza activity increased in Georgia and Israel and remained elevated in Armenia with detections of predominantly influenza A viruses.
• In the Central American and Caribbean countries, influenza activity was at low levels overall. Influenza A(H1N1)pdm09 and A(H3N2) viruses predominated followed by B/Victoria lineage viruses.
• In tropical South America, influenza activity remained low with detections of influenza A viruses reported in some countries.
• In tropical Africa, influenza detections remained low in most reporting countries with a few exceptions and influenza A(H3N2) viruses predominated.
• In Southern Asia, overall influenza activity remained stable at a low level with all seasonal influenza subtypes detected.
• In South-East Asia, influenza positivity overall, driven by all seasonal subtypes, remained elevated, mainly driven by detections in Malaysia and Singapore.
• In the temperate zones of the southern hemisphere, indicators of influenza activity were reported at low levels or below seasonal thresholds in most reporting countries. 
• National Influenza Centres (NICs) and other national influenza laboratories from 124 countries, areas or territories reported data to FluNet for the time period from 05 February 2024 to 18 February 2024* (data as of 01/03/2024 07:48:33 AM UTC). The WHO GISRS laboratories tested more than 544 975 specimens during that time period. 96 018 were positive for influenza viruses, of which 69 483 (72.4%) were typed as influenza A and 26 535 (27.6%) as influenza B. Of the sub-typed influenza A viruses, 6680 (45.8%) were influenza A(H1N1)pdm09 and 7900 (54.2%) were influenza A(H3N2). Of the type B viruses for which lineage was determined, all (10 918) belonged to the B/Victoria lineage.

• Globally, SARS-CoV-2 positivity from sentinel surveillance remained below 10%. Positivity remained below 10% in all WHO Regions with exception of the Region of the Americas where positivity was around 17% and in the Western Pacific Region where positivity increased to 13%. SARS-CoV-2 positivity from non-sentinel surveillance increased to around 18% globally in the most recent week. 
• In countries with RSV surveillance in place, RSV activity was stable or decreased in the USA, Canada, Egypt and most countries in Europe, except the Russian Federation. RSV detections increased slightly in New South Wales of Australia, Mozambique, New Zealand and South Africa.
• 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 89 countries, areas or territories from six WHO regions (African Region: 13; Region of the Americas: 19; Eastern Mediterranean Region: 6; European Region: 36; South-East Asia Region: 8; Western Pacific Region: 7) reported to FluNet from sentinel surveillance sites for the time period from 05 February January 2024 to 18 February 2024* (data as of 01/03/2024 07:48:33 AM UTC). The WHO GISRS laboratories tested more than 33 310 sentinel specimens during that time period and 3038 (9.1%) were positive for SARS-CoV-2. Additionally, more than 823 935 non-sentinel or undefined reporting source samples were tested in the same period and 98 562 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.