Weekly updates, Influenza Epidemiological Week 6 (17 February 2023)

North America: Influenza activity was low overall in the subregion. Influenza A(H1N1)pdm09 continued predominating with the co- circulation of A(H3N2) and B/Victoria. The SARS-CoV-2 and RSV activity decreased. In Canada, influenza activity continues low, with A(H1N1)pdm09 predominance. In Mexico, influenza activity was low, while SARS-CoV-2 and RSV activity remained elevated. In the United States, influenza activity was low overall, with the percentage of deaths due to pneumonia, influenza, and COVID-19 above the average of previous seasons and declining.

Caribbean: Influenza activity decreased in the subregion with A(H1N1)pdm09 predominance, with A(H3N2) and B/Victoria co-circulation. French Guyana and Haiti reported increased influenza activity, and all seasonal subtypes co-circulated. SARS-CoV-2 activity was moderate in the subregion, while RSV activity remained at baseline levels.

Central America: Influenza activity was moderate, with influenza B/Victoria virus predominance and A(H3N2) co-circulation. Guatemala reported increased influenza activity with influenza B/Victoria circulation; SARI activity was low, with 35% of sampled cases positive for RSV. El Salvador and Honduras reported increased influenza activity at low-intensity levels. SARS-CoV-2 percent positivity decreased in the subregion except in Costa Rica and Panama. RSV activity remained elevated in Guatemala.

Andean: Influenza activity was low, predominating influenza A(H1N1)pdm09 viruses; influenza B/Victoria and A(H3N2) viruses co-circulated. In Bolivia and Ecuador, influenza activity was increased at a low-intensity level. SARS-CoV-2 activity was elevated in Ecuador and moderate in Colombia but decreasing. In the subregion, RSV activity was low overall.

Brazil and Southern Cone: Influenza activity was low, with influenza B viruses more frequently detected and co-circulated B/Victoria and A(H1N1)pdm09. Paraguay reported increased influenza B (lineage undetermined) activity at low-intensity levels. Severity indicators were low. SARS-CoV-2 activity was low, except in Brazil and Chile. RSV activity remains elevated in Brazil.

Global: Influenza activity decreased compared to 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 during this reporting period. In Europe, overall influenza detections remained stable, and influenza positivity from sentinel sites increased slightly and remained above the epidemic threshold at the regional level. Half countries reported high or moderate intensity and most reported widespread activity. Overall, influenza A viruses predominated with A(H1N1)pdm09, accounting for most subtyped influenza viruses from primary care sentinel sites but with regional differences. The proportion of influenza B viruses increased in recent weeks. In Central Asia, influenza activity decreased overall. In Northern Africa, activity remained elevated, with continued detections of all seasonal influenza subtypes reported in Morocco and Tunisia. In Western Asia, influenza activity decreased overall with all seasonal influenza subtypes detected, although increased activity continued to be registered in some countries. In East Asia, influenza activity remained low overall, although detections of all seasonal influenza subtypes increased in Mongolia in recent weeks. In tropical Africa, influenza activity was highest in eastern Africa but remained low overall, with detections of all seasonal influenza subtypes. In Southern Asia, influenza activity remained low, with all seasonal influenza subtypes detected. In South-East Asia, detections of predominantly influenza B viruses remained elevated due to continued detections reported in Malaysia. In the temperate zones of the southern hemisphere, influenza activity remained at inter-seasonal levels.

SARS-CoV-2 positivity from sentinel surveillance remained at 20% globally. The activity was reported below 30% in the WHO Region of the Americas, just above 20% in the Western Pacific Region, and remained under 10% in the other regions. SARS-CoV-2 positivity from non- sentinel surveillance was reported at around 25% globally.