Influenza Update N° 447

Overview

29 May 2023, based on data up to 14 May 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 RespiMART (FluNet and FluID) directly or via regional platforms. They are encouraged to enhance integrated surveillance and in southern 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 and WHO guidance.
• Globally, influenza detections decreased further due to a decline in detections in the northern hemisphere, while some countries in the southern hemisphere reported an increase in influenza detections in recent weeks.
• In Oceania, influenza activity increased slightly following trends similar to previous seasons.
• In South Africa, influenza activity increased above the seasonal threshold in pneumonia and influenza-like illness (ILI) surveillance with influenza A viruses predominately detected.
• In temperate South America, influenza activity continued to increase with A(H1N1)pdm09 viruses most frequently detected followed by B viruses, mainly reflecting an increase in Chile.
• In the Caribbean countries, influenza activity remained low overall, although increased activity was reported in a few reporting countries, with influenza A(H1N1)pdm09 and B/Victoria lineage viruses co-circulating.
• overall influenza activity remained elevated though decreasing with detections of predominantly A(H1N1)pdm09 and B viruses. 
• In tropical Africa, influenza detections were low in reporting countries. Influenza A(H1N1)pdm09 viruses predominated among reported detections.
• In Southern Asia, influenza activity remained low with all seasonal subtypes detected.
• In South-East Asia, influenza activity remained stable in most reporting countries, with continued reporting of predominantly A(H1N1)pdm09 and A(H3N2) virus detections.
• In the temperate zones of the northern hemisphere, influenza activity continued to decrease and was reported at low levels or below seasonal threshold in most reporting countries. All seasonal influenza subtypes were detected in similar proportions overall.
• Globally, RSV activity was generally low except in Australia and a few countries in the Region of the Americas. In South Africa, the RSV detection rate among children under five years of age in pneumonia surveillance remained at a low level. RSV activity decreased to low levels in Central America and the Caribbeans while increased in a few countries in tropical and temperate South America.
• National Influenza Centres (NICs) and other national influenza laboratories from 119 countries, areas or territories reported data to FluNet for the time period from 15 May 2023 to 28 May 2023* (data as of 09/06/2023 07:28:47 AM UTC). The WHO GISRS laboratories tested more than 328 524 specimens during that time period. 9814 were positive for influenza viruses, of which 6248 (63.7%) were typed as influenza A and 3566 (36.3%) as influenza B. Of the sub-typed influenza A viruses, 2992 (78.9%) were influenza A(H1N1)pdm09 and 799 (21.1%) were influenza A(H3N2). Of the type B viruses for which lineage was determined, all (499) belonged to the B-Victoria lineage.

• Globally, SARS-CoV-2 positivity from sentinel surveillance increased just above 20%. Activity increased to approximately 35% in the Western Pacific region and remained around 14% and 11% in the Region of the Americas and the European Region, respectively. Activity was around or below 10% in the other regions. SARS-CoV-2 positivity from non-sentinel surveillance was reported around 18% globally. 
• 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 84 countries, areas or territories from six WHO regions (African Region: 14; Region of the Americas: 21; Eastern Mediterranean Region: 4; European Region: 33; South-East Asia Region: 6; Western Pacific Region: 6) reported to FluNet from sentinel surveillance for time period from 15 May 2023 to 28 May 2023* (data as of 09/06/2023 07:28:47 AM UTC). The WHO GISRS laboratories tested more than 47 181 sentinel specimens during that time period and 9606 (20.4%) were positive for SARS‑CoV-2. Additionally, more than 80 989 non-sentinel or undefined reporting source samples were tested in the same period and 13 919 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.