Influenza Update N° 540

Overview

^{Published 20 August 2025 | For reporting Week 32, ending 10 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 remained stable or decreased in most reporting countries. Influenza activity remained elevated in Oceania and some countries in Eastern Africa and South-East Asia. Influenza activity returned to low levels in countries in Tropical and Temperate South America in comparison to recent weeks.
• In the Northern hemisphere, over the past few weeks, influenza activity remained low and stable in most transmission zones except for Western and Middle Africa, Western and Southern 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, East Africa and South-East Asia.
• Influenza A(H1N1)pdm09 predominated in the Americas, Western and Middle Africa, South West Europe, Eastern Asia and Oceania whilst influenza A(H3N2) was the predominant circulating virus in Southern Africa, Western and South-East Asia. In Northern Africa, influenza A and B viruses were detected in similar proportion.  

SARS-CoV-2

• Globally, SARS-CoV-2 positivity remained stable and low, with a few countries reporting elevated positivity rates (>10%) in Central America and the Caribbean, Northern Africa, Europe, and Asia with increases reported in some countries in these zones.
  

Respiratory Syncytial Virus (RSV)

• RSV positivity remained stable and low across reporting countries, with small increases reported only in Central America and the Caribbean and Western Africa. Activity remained elevated in some part of Central America and the Caribbean, and Tropical and Temperate South America where positivity rate 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://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.