Global Respiratory Virus Activity: Weekly Update N° 558

Overview

Globally, influenza activity was elevated with positivity around 25% and increasing in week 50. SARS-CoV-2 activity remained stable and low overall. Influenza predominated and positivity was above 20% in the northern hemisphere temperate and sub-tropical areas, and at 10% in the southern hemisphere temperate and subtropical and the tropical areas.

Influenza

Globally, influenza detections were stable with influenza A viruses predominant among influenza detections in all zones in week 50.

In the northern hemisphere, influenza percent positivity was elevated (>10%) in countries in North America, Central America and the Caribbean, Tropical South America, Northern, Western and Middle Africa, Europe, and Central, Southern, South-East and Western Asia. Percent positivity was over 30% in countries in Central America and the Caribbean, Northern and Western Africa, Northern and South West Europe, and Asia. Increases in activity were observed in countries in North America, Central America and the Caribbean, Northern Africa, Europe, and Western, Southern, South-East and Eastern Asia.

In the southern hemisphere, influenza activity remained low overall although elevated positivity (>10%) was reported in a few countries in Tropical and Temperate South America, Eastern Africa, South-East Asia and Oceania; percent positivity was over 30% in a single country in Oceania. Increases in activity compared to the previous week were observed in single countries in Tropical South America and Oceania.

In the zones with elevated positivity, influenza A(H3N2) was predominant in all zones except Tropical South America and Northern Africa where there was codominance of influenza A(H1N1)pdm09 and A(H3N2).

SARS-CoV-2

Globally, SARS-CoV-2 positivity remained stable and low, with some countries reporting elevated positivity (>10%) in Temperate South America and Europe. Percent positivity was over 30% in a single country in South West Europe. A small increase in activity was reported in a single country in South West Europe.

Respiratory Syncytial Virus (RSV)

RSV activity was stable and low overall although elevated percent positivity (>10%) was reported in few countries in Central America and the Caribbean, Tropical South America, Northern and Western Africa, South West Europe, and Western and Southern Asia. Increases in activity compared to the previous reporting period were reported in countries in these areas except for Southern Asia, where decreases in activity were reported. RSV and influenza activity were both elevated in single countries in Tropical South America and Western Africa.

The next Global Respiratory Virus Activity Weekly Update will be published in the week of 5 January 2026.

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.

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.