WHO releases new information on influenza activity worldwide

Regional offices of the World Health Organization (WHO) and Member States, in collaboration with the Global Influenza Surveillance and Response System (GISRS), collect and report data on influenza activity worldwide every two weeks.

Source: Influenza update no. 432. Image credit: pinkeyes/Shutterstock

National Influenza Centers (NICs) and other national influenza laboratories from 105 countries, territories or territories report data to FluNet.

The latest report, which was updated to 30 October 2022, has data classified by influenza transmission areas, i.e. countries/regions with similar transmission patterns of influenza.

In addition, it covers epidemiological and virological FluNet data for the period 17 October 2022 to 30 October 2022. During this time, WHO’s GISRS laboratories tested over 229,940 samples.

Main highlights

Influenza activity increased globally, and in particular the influenza A(H3N2) virus subtype became dominant. Of the 229,940 samples tested, 15,723 were positive for influenza viruses. The proportion of influenza A and influenza B viruses was 14,589 (92.8%) and 1134 (7.2%). While all characterized B viruses belonged to the B/Victoria lineage, 1424 (21.2%) and 5284 (78.8%) of 14,589 influenza A viruses were H1N1 and H3N2, respectively.

At the global level, while the rise in influenza activity continued in the Northern Hemisphere, it reached a plateau in the Southern Hemisphere. Based on this observation, the WHO recommended that Northern Hemisphere countries, including the United States and Canada, intensify their influenza vaccination campaigns to prevent hospitalizations and deaths. More importantly, doctors should screen or test people for influenza and treat them according to national guidelines.

Despite a large increase in COVID-19 activity in the WHO Americas region and a slight increase in the South-East Asia and Western Pacific regions, sentinel surveillance results showed that it remained below 10% after a long-term downward trend that began in the mid-20s. of the year 2022.

Thus, WHO called for increased integrated surveillance of influenza and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Northern Hemisphere countries. They specifically focused on countries that have received multiplex influenza and SARS-CoV-2 reagent kits from GISRS. WHO even published revised interim guidance for these countries emphasizing the urgent need to report timely epidemiological and laboratory data to their regional and international fora.

Countries with a temperate zone (Northern Hemisphere)

In countries in the temperate zone of the northern hemisphere, such as the United States and Canada, influenza-like illness (ILI) and respiratory virus (RSV) activity increased above the seasonal average for this time of year, with influenza A(H3N2) viruses predominating. SARS-CoV-2 continues to be the leading cause of outbreak mortality in the United States.

Influenza A(H3N2) was predominant in European countries, with the highest ILI activity reported in Southwestern Europe (3.62% positivity). Portugal, followed by Germany and Spain, reported a growing trend in ILI activity. RSV activity was highest in France and steadily increased. Likewise, excess mortality in most age groups continued to rise in European countries. Central (eg, Kazakhstan) and West Asian countries, such as Saudi Arabia, reported high/elevated ILI activity, with influenza B strains predominating in Kazakhstan. On the contrary, in East Asia the activity of influenza A(H3N2) remained stable at intermediate levels.

Temperate countries (Southern Hemisphere)

Overall ILI activity appeared to decrease during this reporting period, except in South America, where ILI activity increased in several countries, such as Argentina, Chile, and Uruguay. In Chile and Uruguay, influenza A(H3N2) viruses were predominant, while influenza B and influenza A(H1N1) were predominant in Argentina. Across the Pacific Islands, including New Zealand, ILI activity remained low except in a few countries. Likewise, in Australia, ILI activity remained low, although testing detected influenza A(H1N1), influenza A(H3N2) and several B viruses.

Tropical countries

The tropical countries of South America and Africa had low ILI activity during the period reported. In particular, RSV activity increased slightly in Brazil. In Puerto Rico and Guatemala, parts of the Caribbean and Central America, ILI activity was above average for this time of year and seasonal threshold.

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