Influenza Update N° 537

Overview

^{Published 30 July 2025 | For reporting Week 29, ending 20 July 2025}

Influenza

• Globally, influenza activity remained low with influenza A viruses predominant.
• In the Southern Hemisphere, over the past few weeks, trends in influenza activity varied by transmission zone, with an increasing trend in Oceania and a decreasing trend in Temperate and Tropical South America and Southern Africa. Compared to the previous week, influenza activity remained stable in most countries with a small increase reported from a single country in Tropical South America. Influenza positivity remained elevated in countries in Temperate and Tropical South America, Eastern Africa, South-East Asia and Oceania, and was over 30% in parts of Oceania.
• In the Northern Hemisphere, over the past few weeks, influenza activity mostly remained low and stable in most transmission zones except for Western Africa where an increasing trend was observed. Compared to the previous week, influenza remained stable in most countries with mostly small increases reported from single countries in Western Africa, Northern Europe, Southern and South-East Asia. Influenza positivity was elevated in Central America and the Caribbean, Tropical South America, Northern Europe, Western Africa, South-East Asia, and was over 30% in parts of Southern Asia.
• Influenza A(H1N1)pdm09 predominated in the Americas, Western Africa and Oceania whilst influenza A(H3N2) was the predominant circulating virus Western, Eastern and Southern Asia. Influenza A(H1N1)pdm09 and influenza A(H3N2) were co-dominant in Eastern Africa and South-East Asia.

 

SARS-CoV-2

• Globally, SARS-CoV-2 positivity remained stable and low across the majority of reporting countries. Positivity was elevated (>10%) in a few countries in Central America and the Caribbean, Northern and South West Europe, Northern and Eastern Africa, Western, Eastern, Southern and South-East Asia. Increases were reported in countries in Central America and the Caribbean, Eastern and Northern Europe, Eastern and Southern Asia.

 

Respiratory Syncytial Virus (RSV)

• Among reporting countries, RSV positivity remained stable and low overall, however, increases were reported in countries in Temperate South America.Elevated activity was reported in a few countries in Central America and the Caribbean, Tropical and Temperate South America and activity was over 30% in parts of Central America and the Caribbean and Temperate South America.

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 https://covid.comesa.int/publications/i/item/WHO-2019-nCoV-integrated_sentinel_surveillance-2022.1.
 

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.