Global Respiratory Virus Activity: Weekly Update N° 559

Overview

End-of year holiday season may affect the surveillance testing and reporting practices in one or more regions. Globally, influenza activity continued to increase and was elevated with positivity above 25% over the last few weeks. SARS-CoV-2 activity remained stable and low overall. Influenza predominated and positivity was around 30% in the northern hemisphere temperate and sub-tropical areas, and above 10% in the tropical areas. In the southern hemisphere temperate and subtropical areas, SARS-CoV-2 predominated with positivity around 10%.

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 52.

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

In the southern hemisphere, influenza activity remained stable and low overall with elevated positivity (>10%) reported in a few 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 influenza A(H1N1)pdm09 was predominant.

SARS-CoV-2

Globally, SARS-CoV-2 positivity remained stable and low, with some countries reporting elevated positivity (>10%) in Temperate South America and South West and Eastern Europe. Percent positivity was over 20% in a single country in South West Europe. Small increases in activity were reported in single countries in Temperate South America and Eastern Africa.

Respiratory Syncytial Virus (RSV)

RSV activity was stable and low overall although elevated percent positivity (>10%) was reported in a few countries in Central America and the Caribbean, Western Africa, Northern Europe, and Western and Southern Asia. Increases in activity were reported in single countries in Central America and the Caribbean and Western Asia. RSV and influenza activity were both elevated in a few countries in Central America and the Caribbean, Western Africa, Northern Europe, and Western and Southern Asia.

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.