Influenza Update N° 458

Overview

13 November 2023, based on data up to 29 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 Eastern and Western Asia.
• In the countries of North America, influenza detections remained low with indicators of influenza activity at levels typically observed between influenza seasons.
• In Europe and Central Asia, in the most recent week, influenza activity remained below baseline or at low levels in all but two reporting countries, where activity was medium. Among the few influenza detections in primary care sentinel surveillance, influenza A viruses predominated.
• In Northern Africa, no influenza detections were reported for this period. However, Egypt reported predominantly influenza A(H1N1)pdm09 activity in the weeks prior to this reporting period.
• In East Asia, influenza activity continued to increase mainly due to activity in the southern provinces of China and the Republic of Korea, with influenza A(H3N2) and A(H1N1)pdm09 viruses more frequently detected, respectively.
• In Western Asia, influenza activity continued to increase in some countries of the Arab Peninsula and remained low in other reporting countries.
• In the Central American and Caribbean countries, influenza increased slightly in the Caribbean with detections of predominantly influenza A(H1N1)pdm09 and A(H3N2) viruses, and remained low in Central America with detections of predominantly B/Victoria lineage viruses.
• In tropical Africa, influenza detections decreased and were low overall. Influenza A(H3N2) viruses were predominant but all seasonal influenza subtypes were reported.
• In Southern Asia, influenza activity increased due to increased detections of predominantly influenza A viruses in Iran (Islamic Republic of). Detections decreased or were low in other reporting countries.
• In South-East Asia, influenza activity remained elevated with influenza A(H1N1)pdm09 and influenza A(H3N2) viruses predominant. Influenza detections continued to increase in Lao People’s Democratic Republic and Thailand, with influenza A(H1N1)pdm09 and A(H3N2) predominant. Detections decreased or were low in other reporting countries.
• In the temperate zones of the southern hemisphere, indicators of influenza activity were reported at low levels or below seasonal threshold in reporting countries.
• National Influenza Centres (NICs) and other national influenza laboratories from 109 countries, areas or territories reported data to FluNet for the period from 16 October 2023 to 29 October 2023 (data as of 10/11/2023 06:08:00 AM UTC). The WHO GISRS laboratories tested more than 262 187 specimens during that period. 14 448 were positive for influenza viruses, of which 12 366 (86.0%) were typed as influenza A and 2082 (14.4%) as influenza B. Of the sub-typed influenza A viruses, 3251 (32.6%) were influenza A(H1N1)pdm09 and 6720 (67.4%) were influenza A(H3N2). Of the type B viruses for which lineage was determined, all (1295) belonged to the B/Victoria lineage. 

• Globally, SARS-CoV-2 positivity from sentinel surveillance decreased to 6%. Positivity increased slightly but remained low in the African Region and remained low in the South-East Asia Region. Positivity decreased in the Region of the Americas and the Eastern Mediterranean Region and remained stable in the European Region around 11% In the Western Pacific Region, activity increased slightly to around 12%. SARS-CoV-2 positivity from non-sentinel surveillance increased to around 20% globally.
• In countries with RSV surveillance in place, RSV activity was generally low or decreasing except in some countries in Europe, central America and the Caribbean. Early signs of RSV activity were noted in Canada and the United States of America.
• 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 76 countries, areas or territories from six WHO regions (African Region: 15; Region of the Americas: 18; Eastern Mediterranean Region: 4; European Region: 28; South-East Asia Region: 5; Western Pacific Region: 6) reported to FluNet from sentinel surveillance sites for time period from 16 October 2023 to 29 October 2023 (data as of 10/11/2023 06:08:00 AM UTC). The WHO GISRS laboratories tested more than 26 817 sentinel specimens during that period and 1610 (6.0%) were positive for SARS-CoV-2. Additionally, more than 26 230 non-sentinel or undefined reporting source samples were tested in the same period and 4681 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) hosted by WHO RespiMART platform and influenza and other respiratory virus reports from WHO Regional Offices and Member States. During the COVID-19 pandemic, FluNet has also been receiving updates on testing of samples obtained from routine influenza surveillance systems for SARS-CoV-2. 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.