Global Respiratory Virus Activity: Weekly Update N° 563

Overview

Globally, influenza activity continued to decrease over the past three weeks but positivity remained elevated around 15% in week 4 2026. SARS-CoV-2 activity remained low overall. Influenza predominated and positivity was around 15% in the northern hemisphere temperate and subtropical areas and in the tropical areas. In the southern hemisphere temperate and subtropical areas, influenza and SARS-CoV-2 positivity were both low.

Influenza

Globally, influenza detections continued to decline and influenza A viruses were predominant among influenza detections in week 4.

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

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

In the zones with elevated positivity, influenza A(H3N2) was predominant in most of the zones except Central America and the Caribbean and Tropical South America where there was codominance of influenza A(H1N1)pdm09 and A(H3N2), and Eastern Africa where there was codominance of influenza A(H1N1)pdm09, A(H3N2) and B viruses.

SARS-CoV-2

Globally, SARS-CoV-2 positivity remained stable and low, with single countries reporting elevated positivity (>10%) in Temperate South America and South West Europe.

Respiratory Syncytial Virus (RSV)

Globally, RSV positivity remained stable and low, with single countries reporting elevated positivity (>10%) in Central America and the Caribbean, Western Africa, Northern and South West Europe and Western Asia. Small increases in activity were reported in single countries in Central America and the Caribbean and South West Europe. RSV and influenza activity were both elevated in single countries in Central America and the Caribbean, Western Africa, 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 the northern hemisphere temperate and subtropical areas, influenza-specific transmissibility was reported as moderate (2); transmissibility using syndromic data was reported as below seasonal threshold (9), low (15), moderate (8) and high (3). Influenza-specific transmissibility was reported as below seasonal threshold and low in single countries in the tropical areas and southern hemisphere temperate and subtropical areas, respectively.

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.