Weekly updates, Influenza Epidemiological Week 10 (17 March 2023)

North America: Influenza virus activity decreased throughout the sub-region, with the predominance of influenza A(H1N1)pdm09. Influenza A(H3N2)pdm09 and B/Victoria co-circulated. SARS-CoV-2 circulates at moderate levels, while RSV activity remains low. In Canada, influenza activity was low, with influenza B virus predominance. In Mexico, influenza activity was low, with elevated SARS-CoV-2 and RSV activity. In the United States, influenza and RSV activity were low, while SARS-CoV-2 activity remained elevated. 

Caribbean: Influenza activity decreased, with influenza A and B viruses equally detected. Influenza A(H1N1)pdm09 and B/Victoria co-circulated. Belize reported increased influenza activity. Overall, SARS-CoV-2 activity was low in the subregion, except in Dominica and Jamaica, where it was moderate. RSV was moderate in Jamaica; elsewhere in the subregion, RSV activity was low. 

Central America: Influenza activity was moderate overall, with influenza B/Victoria virus predominance. Influenza A(H3N2) and A(H1N1)pdm09 co-circulated. Honduras reported increased influenza activity, while Guatemala and Panama had moderate activity. SARS-CoV-2 percent positivity dropped in the subregion, except in Costa Rica. RSV activity was low overall. 

Andean: Influenza activity was low, predominating influenza B/Victoria viruses; influenza A(H1N1)pdm09 and A(H3N2) viruses co-circulated. Bolivia, Ecuador, and Venezuela reported increased influenza activity. In Bolivia, SARI cases / 100 hospitalizations were moderate, and 14% tested positive for influenza. SARS-CoV-2 and RSV activity were low overall. 

Brazil and Southern Cone: Influenza activity was at interseason levels; influenza B viruses were detected more frequently, with B/Victoria and A(H1N1)pdm09 co-circulation. Increased SARS-CoV-2 activity was reported in Brazil and Chile, while RSV was elevated in Brazil. 

Global: Influenza activity continued to decrease following the peak in late 2022. Influenza A viruses predominated, with a slightly larger proportion of A(H1N1)pdm09 viruses detected among the subtyped influenza A viruses. The proportion of influenza B virus detections increased recently. In Europe, overall influenza detections decreased slightly, and influenza positivity from sentinel sites decreased, although remaining above the epidemic threshold at the regional level. Out of 39 countries, 17 reported high or moderate intensity, and over half continued to report widespread activity. Overall, influenza B viruses were predominated in both sentinel, and non-sentinel surveillance as all subregions experienced a wave of influenza B activity after an initial influenza A wave. Influenza detections decreased or were stable in most countries except Belarus, Croatia, Hungary, Luxembourg, and Montenegro, where increases were reported. In Central Asia, influenza activity decreased overall. In Northern Africa, detections of influenza A and B viruses continued to decline in Morocco and Tunisia. In Western Asia, influenza activity continued to be reported in some countries with detections of all seasonal influenza subtypes. In East Asia, influenza activity of predominantly A(H1N1)pdm09 steeply increased in China but decreased in the other reporting countries. In tropical Africa, influenza activity increased in some countries of Western Africa, while detections were low across reporting countries in Middle and Eastern Africa. In Southern Asia, influenza activity remained low, with influenza A(H3N2) and B/Victoria lineage viruses mainly detected. In South-East Asia, influenza activity remained elevated, with influenza B mainly detected in Malaysia and A(H3N2) in Singapore and Thailand. In the temperate zones of the Southern Hemisphere, influenza activity remained at the inter-seasonal level. RSV activity was generally low or decreasing globally, except in South Africa, where activity remained high. 

SARS-CoV-2 positivity from sentinel surveillance remained around 20% globally. Activity remained at about 25% in the WHO Region of the Americas and increased to 15% in the Eastern Mediterranean and Western Pacific Regions. Activity remained below 10% in the other regions. SARS-CoV-2 positivity from non-sentinel surveillance was reported at around 30% globally. 

Avian Influenza: A summary of the avian influenza situation in the region, case management and recommendations are available at Epidemiological alerts and updates | PAHO/WHO | Pan American Health Organization (paho.org)