Global Respiratory Virus Activity: Weekly Update N° 561

Overview

End-of year holiday season may affect the surveillance testing and reporting practices in one or more regions. Globally, influenza activity was elevated with positivity just under 20% in week 2 2026. SARS-CoV-2 activity remained stable and low overall. Influenza predominated and positivity was around 20% in the northern hemisphere temperate and sub-tropical areas, and just under 20% in the tropical areas. In the southern hemisphere temperate and subtropical areas, SARS-CoV-2 predominated although positivity was under 10% and influenza positivity was low at under 5%.

Influenza

Globally, influenza detections appeared to decline; however, this could be an artifact due to delayed reporting in some regions. Influenza A viruses were predominant among influenza detections in all zones in week 2.

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

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

In the zones with elevated positivity, influenza A(H3N2) was predominant in all zones except Tropical South America 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 single countries reporting elevated positivity (>10%) in South West and Eastern Europe and two countries in Temperate South America. A small increase in activity was reported in a single country in Temperate South America.

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, South West and Northern Europe, and Western Asia. Increases in activity compared to the previous reporting period were reported in a few countries in South West and Northern Europe. RSV and influenza activity were both elevated in single countries in Central America and the Caribbean, Northern and South West Europe, and Western Asia.

Severity assessment

The severity assessments here are reported from countries, areas and territories. Assessments for transmissibility can be reported based on syndromic parameters and/or influenza-specific parameters. In northern hemisphere temperate and subtropical areas, influenza-specific transmissibility was reported as below seasonal threshold (1) and moderate (1); transmissibility using syndromic data was reported as below seasonal threshold (9), low (12) and moderate (12). In tropical areas, influenza-specific transmissibility was reported as below seasonal threshold in a single country.

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.