Influenza Update N° 539

Overview

^{Published 18 August 2025 | For reporting Week 31, ending 03 August 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 decreased overall, although with different trends reported across geographical regions. Influenza activity remained elevated in Oceania and some countries in Tropical and Temperate South America, Eastern Africa and South-East Asia. Compared with the previous week, most countries reported stable activity, with a small increase in countries in Oceania. 
• In the Northern hemisphere, over the past few weeks, influenza activity remained low and stable in most transmission zones except for Tropical South America, Western, Middle and Eastern Africa, Southern and South-East Asia where an increasing trend was observed and percent positivity was over 30% in some countries. Influenza positivity remained elevated but stable also in some countries in Central America and the Caribbean.
• Influenza A(H1N1)pdm09 predominated in the Americas, Western and Middle Africa, South West Europe and Oceania whilst influenza A(H3N2) was the predominant circulating virus in Eastern and Southern Africa, Northern Europe, and in Asia. Influenza B predominated in Northern Africa.

 

SARS-CoV-2

• Globally, SARS-CoV-2 positivity remained stable and low overall, with a few countries reporting elevated positivity (>10%). Increases were reported in countries in Central America and the Caribbean, Western Africa, Northern and Eastern Europe, Western and Eastern Asia.

 

Respiratory Syncytial Virus (RSV)

• RSV positivity remained stable and low across reporting countries, with small increases reported only in Central America and the Caribbean. Activity remained elevated in some part of Central America and the Caribbean, and Tropical and Temperate South America where positivity was over 30% in a few countries.

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.