Influenza Update N° 434

Overview

28 November 2022, based on data up to 13 November 2022

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 co-circulation of influenza and SARS-CoV-2 viruses. They are encouraged to enhance integrated surveillance and in northern hemisphere countries step-up their influenza vaccination campaign to prevent severe disease and hospitalizations associated with influenza. Clinicians should consider influenza in differential diagnosis, especially for high-risk groups for influenza, and test and treat according to national guidance. Because of changes in surveillance of respiratory viruses during the COVID-19 pandemic, comparisons of current data with that from previous seasons may not always be valid and data should be interpreted with caution.
• Globally, influenza activity increased and where subtyped, influenza A(H3N2) viruses predominated.
• In the countries of North America, influenza positivity and influenza-like-illness (ILI) activity continued to increase steeply in recent weeks. Many indicators were above levels typically observed at this time of year and some are near or above levels observed at the peak of previous epidemics. Influenza A(H3N2) was the predominant virus detected.
• In Europe, overall influenza activity continued to increase with influenza positivity from sentinel sites remaining above the epidemic threshold at the regional level. Influenza A viruses predominated among the reported detections in general, with A(H3N2) viruses accounting for the majority of subtyped influenza A viruses from sentinel sites and influenza A(H1N1)pdm09 viruses predominant among non-sentinel samples.
• In central Asia, influenza B virus activity continued to be reported from Kazakhstan and other countries reporting a few influenza A and B virus detections.
• In Northern Africa, influenza detections were low in reporting countries.
• In Western Asia, influenza activity appeared to decrease overall with all seasonal influenza subtypes detected in similar proportions.
• In East Asia, influenza activity of predominantly influenza A(H3N2) remained low overall among reporting countries but with some increases reported in southern China and the Republic of Korea. ​
• In the Caribbean and Central American countries, influenza activity of predominately influenza A(H3N2) increased in Mexico but remained low in most other reporting countries.
• In the tropical countries of South America, influenza detections were low and A(H3N2) viruses predominated followed by influenza B/Victoria lineage viruses.
• In tropical Africa, influenza activity remained low with detections of all seasonal influenza subtypes reported.
• In Southern Asia, influenza activity decreased this period mainly due to decreased activity reported in Iran (Islamic Republic of). Influenza A(H3N2) was the most frequently detected subtype in the subregion.
• In South-East Asia, detections of predominantly influenza A(H3N2) and influenza B continued to decrease.
• In the temperate zones of the southern hemisphere, influenza activity was low in most reporting countries, except in temperate South America where activity remained elevated in Argentina and Chile.
• National Influenza Centres (NICs) and other national influenza laboratories from 125 countries, areas or territories reported data to FluNet for the time period from 14 November 2022 to 27 November 2022 * (data as of 2022-12-09 08:20:25 UTC). The WHO GISRS laboratories tested more than 560 422 specimens during that time period. 93 082 were positive for influenza viruses, of which 91 170 (97.9%) were typed as influenza A and 1912 (2.1%) as influenza B. Of the sub-typed influenza A viruses, 2203 (14.4%) were influenza A(H1N1)pdm09 and 13 091 (85.6%) were influenza A(H3N2). Of the characterized B viruses (400), 100% belonged to the B/Victoria lineage.

• Globally, COVID-19 positivity from sentinel surveillance increased to just over 10%, after a long-term downtrend beginning in mid-2022. Activity appeared to increase in the Region of the Americas with percent positivity around 14%, and in the South-East Asia Region with positivity just below 10%. In the European Region, positivity was stable slightly below 10%. In the African and Eastern Mediterranean and Western Pacific Regions, positivity remained below 10%. Globally, COVID-19 positivity from non-sentinel surveillance increased in recent weeks to around 25%.
  
• During the COVID-19 pandemic, 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. Revised interim guidance has just been published here: https://www.who.int/publications/i/item/WHO-2019-nCoV-integrated_sentinel_surveillance-2022.1.
• National Influenza Centres (NICs) and other national influenza laboratories from 73 countries, areas or territories from six WHO regions (African Region: 10; Region of the Americas: 18; Eastern Mediterranean Region: 5; European Region: 31; South-East Asia Region: 4; Western Pacific Region: 5) reported to FluNet from sentinel surveillance sites for the time period from 14 November 2022 to 27 November 2022* (data as of 2022-12-09 08:20:24 UTC). The WHO GISRS laboratories tested more than 49 444 sentinel specimens during that time period and 4743 (9.6%) were positive for SARS-CoV-2. Additionally, more than 220 234 non-sentinel or undefined reporting source samples were tested in the same period and 43 679 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.