Influenza Update N° 543

Overview

^{Published 10 September 2025 | For reporting Week 35, ending 31 August 2025}

Influenza

• Globally, influenza activity remained low, with influenza A viruses continuing to predominate. Different patterns were observed across hemispheres and geographic areas.
• In the southern hemisphere, influenza activity remained stable in reporting countries. Influenza positivity remained elevated (>10%) in Eastern Africa, South-East Asia and Oceania.
• In the northern hemisphere, over the past few weeks, influenza activity remained low and stable in most geographic areas. Influenza positivity was elevated in Central America and the Caribbean, Western and Middle Africa, Northern Europe, and Western, Southern and South-East Asia and percent positivity was over 30% in some countries. An increase in activity was observed in Western Africa, as well as in Southern and South-East Asia.
• In the geographic areas with elevated positivity, influenza A(H1N1)pdm09 predominated in Central America and the Caribbean, Western Africa, Northern Europe and Oceania whilst influenza A(H3N2) was the predominant circulating virus in Southern and South-East Asia. Influenza A(H1N1)pdm09 and influenza A(H3N2) were codominant in Eastern Africa and Western Asia.

 

SARS-CoV-2

• Globally, SARS-CoV-2 positivity remained low but increased slightly, with a few countries reporting elevated positivity (>10%) in Central America and the Caribbean, Tropical South America, Northern Africa, Europe, Western, Southern, Eastern and South-East Asia. Small increases in activity were reported some countries in Central America and the Caribbean, Tropical South America, Europe and South-East Asia.

 

Respiratory Syncytial Virus (RSV)

• RSV positivity remained elevated in some countries in Central America and the Caribbean, Tropical and Temperate South America, Western Africa and Eastern Asia. RSV positivity rates were over 30% in a single country in Central America and the Caribbean. RSV positivity remained stable and low across the majority of reporting countries, with a small increase in activity reported in one country in Western Africa.

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.
 

Starting with report #501, the Global Respiratory Virus Activity Weekly Update included data from sentinel surveillance and other types of systematically conducted virologic surveillance. Countries, areas, and territories use a variety of approaches to monitor respiratory virus activity and data in this report may vary from surveillance reports posted elsewhere. Analyses stratified by source of surveillance is available through Respimart.