Influenza Update N° 440

Overview

06 March 2023, based on data up to 19 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 and report to FluNet and FLUID directly or via regional platforms. 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 should be interpreted with caution.
• Globally, influenza activity continued to decrease following the peak in late 2022. Influenza A viruses predominated with a slightly larger proportion of A(H1N1)pdm09 viruses detected among the subtyped influenza A viruses. The proportion of influenza B virus detections increased during this reporting period.
• In the countries of North America, most indicators of influenza activity decreased to levels similar or below levels typically observed towards the end of the season. Influenza A viruses predominated and influenza A(H3N2) accounted for the majority of subtyped influenza A viruses in the United States of America (USA), whereas A(H1N1)pdm09 accounted for the majority of subtyped influenza A viruses in Canada.
• In Europe, overall influenza detections remained stable and influenza positivity from sentinel sites increased in the most recent week, remaining above the epidemic threshold at the regional level. Out of 39 countries, 18 reported high or moderate intensity, and over half continued to report widespread activity. Overall, influenza A and B viruses were detected at similar proportions in both sentinel and non-sentinel surveillance. The proportion of influenza B viruses increased in recent weeks. Other indicators of influenza activity remained stable or decreased in most countries while a few countries reported increases.
• In Central Asia, influenza activity decreased overall. ​
• In Northern Africa, activity driven by all seasonal influenza subtypes was low and continued to decrease in Morocco and Tunisia.
• In Western Asia, influenza activity continued to be reported in some countries with detections of all seasonal influenza subtypes.
• In East Asia, influenza activity of predominantly A(H1N1)pdm09 steeply increased in China but decreased in the other reporting countries.
• In the Caribbean and Central American countries, influenza activity of mainly influenza A(H3N2) and B viruses continued to decrease.
• In the tropical countries of South America, influenza remained low with all seasonal subtypes co-circulating and influenza B/Victoria predominant
• In tropical Africa, influenza activity was highest in eastern Africa but remained low overall with detections of all seasonal influenza subtypes reported.
• In Southern Asia, influenza activity remained low with all seasonal influenza subtypes detected.
• In South-East Asia, detections of predominantly influenza B viruses remained elevated, mainly due to continued detections in Malaysia.
• In the temperate zones of the southern hemisphere, influenza activity remained at inter-seasonal levels.
• Globally, RSV activity was generally low or decreasing.
• National Influenza Centres (NICs) and other national influenza laboratories from 112 countries, areas or territories reported data to FluNet for the time period from 06 February 2023 to 19 February 2023 (data as of 2023-03-10 10:39:46 UTC). The WHO GISRS laboratories tested more than 452 053 specimens during that time period. 31912 were positive for influenza viruses, of which 18760 (58.8%) were typed as influenza A and 13152 (41.2%) as influenza B. Of the sub-typed influenza A viruses, 4159 (66.2%) were influenza A(H1N1)pdm09 and 2144 (33.8%) were influenza A(H3N2). Of the characterized B viruses, 100% (1094) belonged to the B/Victoria lineage.

• SARS-CoV-2 positivity from sentinel surveillance remained around 20% globally. Activity was around 25% in the WHO Region of the Americas, decreased to around 10% in  in the Western Pacific Region and remained under 10% in the other regions. SARS-CoV-2 positivity from non-sentinel surveillance was reported around 25% globally. 
• 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. The guidance can be found 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 81 countries, areas or territories from six WHO regions (African Region: 12;  Region of the Americas: 19;  Eastern Mediterranean Region: 5;  European Region: 36;  South-East Asia Region: 3;  Western Pacific Region: 6) reported to FluNet from sentinel surveillance sites for time period from 06 February 2023 to 19 February 2023 (data as of 2023-03-02 10:39:46 UTC). The WHO GISRS laboratories tested more than 42 664 sentinel specimens during that time period and 8182 (19.2%) were positive for SARS-CoV-2. Additionally, more than 118 121 non-sentinel or undefined reporting source samples were tested in the same period and 30 995 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.