Influenza Update N° 544

Overview

^{Published 17 September 2025 | For reporting Week 36, ending 7 September 2025}

Influenza

• Globally, influenza activity remained low, with influenza A viruses continuing to predominate. Different patterns were observed across hemispheres and transmission zones.
• In the Southern hemisphere, influenza activity remained low and stable in most reporting countries with elevated positivity (>10%) observed in single countries 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 transmission zones. Influenza positivity was elevated in Central America and the Caribbean, Western and Middle Africa, Western, Southern and South-East Asia and percent positivity was over 30% in some countries. An increase in activity was observed in South-West Europe, Western, Southern and South-East Asia.
• In the transmission zones with elevated positivity, influenza A(H1N1)pdm09 predominated in Central America and the Caribbean, Western Africa and Middle Africa, and Oceania whilst influenza A(H3N2) was the predominant circulating subtype in Eastern Africa, Western, Southern and South-East Asia.

 

SARS-CoV-2

• Globally, SARS-CoV-2 positivity remained at low levels but increased, with reporting elevated positivity (>10%) observed in Central America and the Caribbean, Tropical South America, Europe, Western and Eastern Asia. Small increases in activity were reported some countries in Tropical South America, Europe and Eastern 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 and Western Africa. RSV positivity remained stable and decrease across the majority of reporting countries, with a small increase in activity reported in one country in Central America and the Caribbean.

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.
 

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.