^{Published 8 October 2025 | For reporting Week 39, ending 28 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 and South-East Asia. An increase in activity was observed in a single country in South-East Asia.
• 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 a few countries. An increase in activity was observed in countries in Central America and the Caribbean, Western and Middle Africa, Southern and South-East Asia.
• In the transmission zones with elevated positivity, influenza A(H1N1)pdm09 predominated in Central America and the Caribbean, Eastern and Middle Africa whilst influenza A(H3N2) was the predominant circulating subtype in Asia. Influenza A(H1N1)pdm09 and influenza A(H3N2) were codominant in Western Africa.

SARS-CoV-2

• Globally, SARS-CoV-2 positivity increased but remained at low levels, with reporting elevated positivity (>10%) observed in North America, Central America and the Caribbean, Tropical South America, Europe, Western and Eastern Asia and percent positivity was over 30% in a few countries. Increases in activity were reported in two countries in South-West Europe and one country in Tropical South America.

Respiratory Syncytial Virus (RSV)

• RSV positivity remained elevated in some countries in Central America and the Caribbean, Tropical and Temperate South America and Western Africa. RSV positivity remained stable across the majority of reporting countries, with a small increase in activity reported in one country in Central America and the Caribbean.

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.