Influenza Update N° 446

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 the countries of North America, most indicators of influenza activity were at levels typically observed between influenza seasons. Influenza B viruses predominated in Canada and the United States of America (USA).
• In Europe, overall influenza detections decreased and influenza positivity from sentinel sites decreased to 4%, below the epidemic threshold of 10% at the regional level. All countries reported low or below baseline intensity. The number of countries reporting widespread activity decreased to four out of 36. Overall, influenza B viruses predominated in both sentinel and non-sentinel surveillance as all subregions experienced a wave of influenza B activity after an initial influenza A wave. Only four countries (Germany, Poland, Slovakia and Slovenia) reported influenza positivity above 10% in sentinel primary care. Influenza detections were low in all reporting countries.
• In Central Asia, no influenza detections were reported this period despite continued testing.).
• In Northern Africa, influenza detections were low in reporting countries.
• In Western Asia, influenza activity remained low overall with detections of all seasonal influenza subtypes.
• In Eastern Asia, influenza activity decreased overall, although influenza detections increased slightly in the Republic of Korea in recent weeks.
• In the Caribbean countries, influenza activity increased but remained low with influenza B/Victoria lineage viruses predominant. In Central American countries, influenza activity increased slightly with A(H1N1)pdm09 viruses accounting for just over half the influenza detections in recent weeks. In Mexico, influenza activity increased to a moderate level with B/Victoria lineage virus detections increasing slightly over the past few weeks.
• In the tropical countries of South America, influenza activity decreased overall during this reporting period although positivity remained at an extraordinary level in Bolivia (Plurinational State of).
• 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 was stable, with continued reporting of predominantly A(H1N1)pdm09 virus detections from Malaysia, and A(H3N2) virus detections from Singapore. Other countries reported predominantly A(H1N1)pdm09 virus detections.
• In the temperate zones of the southern hemisphere, influenza activity remained low, however influenza activity increased in Australia, Chile, in pneumonia surveillance in South Africa (indicating the start of the season), and in SARI cases in New Zealand. Influenza A viruses were predominant and among the subtyped viruses and influenza A(H1N1)pdm09 predominated in these countries.
• Globally, RSV activity was generally low except in Australia and a few countries in the Region of the Americas. RSV activity decreased but remained elevated in parts of Australia. In South Africa, the RSV detection rate among children under five years of age in pneumonia surveillance remained at a low level. RSV increased in several countries in tropical and temperate South America.
• National Influenza Centres (NICs) and other national influenza laboratories from 115 countries, areas or territories reported data to FluNet for the time period from 01 May 2023 to 14 May 2023* (data as of 26/05/2023 9:06:27 AM UTC). The WHO GISRS laboratories tested more than 319 245 specimens during that time period. 13 436 were positive for influenza viruses, of which 9548 (71.06%) were typed as influenza A and 3888 (28.94%) as influenza B. Of the subtyped influenza A viruses, 4997 (68.79%) were influenza A(H1N1)pdm09 and 2267 (31.21%) were influenza A(H3N2). Of the type B viruses for which lineage was determined, all belonged to the B/Victoria lineage.

• SARS-CoV-2 positivity from sentinel surveillance increased to 17% globally. Activity increased to over 30% in the Western Pacific region, remained around 20% in the Eastern Mediterranean 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 20% 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://covid.comesa.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: 11; Region of the Americas: 20; Eastern Mediterranean Region: 4; European Region: 36; South-East Asia Region: 5; Western Pacific Region: 5) reported to FluNet from sentinel surveillance sites for time period from 01 May 2023 to 14 May 2023* (data as of 26/05/2023 9:06:27 AM UTC). The WHO GISRS laboratories tested more than 46 326 sentinel specimens during that time period and 9114 (19.67%) were positive for SARS‑CoV-2. Additionally, more than 685 339 non-sentinel or undefined reporting source samples were tested in the same period and 16 291 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.