Weekly updates, Influenza Epidemiological Week 52 (30 December 2022)

North America: Influenza activity was moderate, although decreasing in the subregion, with the predominance of influenza A(H3N2) and co-circulation of A(H1N1)pdm09 and B/Victoria. The SARS-CoV-2 activity has increased, while RSV activity continued to decline. In Canada, influenza activity has decreased; most surveillance indicators were within expected levels. In Mexico, influenza activity continued above expected levels, with SARI cases at low-intensity levels. In the United States, influenza activity declined at low-intensity levels, with the percentage of deaths due to pneumonia, influenza, and COVID-19 above the average of previous seasons. RSV activity is high but continues to decrease.

Caribbean: Influenza activity was moderate in the subregion with A(H3N2) virus predominance and A(H1N1)pdm09 co-circulation. The Dominican Republic reported increased influenza activity with influenza A(H3N2) circulation. SARS-CoV-2 activity remained low overall; however, Haiti and Dominica have shown increased COVID-19 activity, while Jamaica registered increased RSV activity.

Central America: Influenza activity was at moderate levels, with the predominance of influenza A(H3N2) and the co-circulation of influenza B/Victoria (where lineage was determined). Increased influenza activity was reported in Honduras, with the circulation of influenza B (lineage undetermined). SARS-CoV-2 percent positivity decreased in the subregion overall, with an increased percent positive in Costa Rica, while in Guatemala, RSV activity was elevated.

Andean: Influenza activity was low, but increasing, with the predominance of influenza A(H3N2) and co-circulation of influenza A(H1N1)pdm09 and B/Victoria. Bolivia and Ecuador reported increased influenza activity at extraordinary and moderate-intensity levels, with increased SARI activity at low-intensity levels in both countries. In addition, SARS-CoV-2 percent positivity continued raised in Bolivia, Colombia, Ecuador, and Peru, but with a declining trend. In the subregion, RSV activity was low overall.

Brazil and Southern Cone: Influenza activity decreased to low levels, with influenza A(H3N2) predominance and co-circulation of influenza A(H1N1)pdm09 and influenza B/Victoria. Argentina reported decreasing influenza activity with influenza B (lineage undetermined). In Chile, influenza A(H3N2) predominated, showing a decreasing trend. In Paraguay, influenza activity was low, with A(H3N2) circulating. The SARS-CoV-2 activity was elevated across the subregion but with a decreasing trend. Increased RSV activity continued to be reported in Brazil and Chile.

Global: Influenza activity remained elevated due to activity in the northern hemisphere. Where subtyped, influenza A viruses predominated, with a slightly larger proportion of A(H3N2) viruses detected among the subtyped influenza A viruses. In Europe, overall influenza activity continued to increase, with influenza positivity from sentinel sites remaining above the epidemic threshold at the regional level. Influenza A viruses predominated with A(H3N2) viruses accounting for most subtyped influenza viruses from sentinel sites but with regional differences. Half of reporting countries signaled high or very high intensity. In central Asia, influenza activity increased with influenza A(H1N1)pdm09 viruses predominant, followed by influenza B viruses. In Northern Africa, influenza detections increased among reporting countries with all seasonal subtypes detected. In Western Asia, influenza activity decreased overall with all seasonal influenza subtypes detected, though increased activity was reported in some countries in the transmission zone. In East Asia, influenza activity of predominantly influenza A(H3N2) viruses remained low overall among reporting countries but with increases reported in Mongolia and the Republic of Korea. In tropical Africa, influenza activity remained low, with detections of all seasonal influenza subtypes reported. However, activity increased in some countries in Eastern Africa. In Southern Asia, influenza activity remained low, mainly due to decreased activity reported in Iran (Islamic Republic of). Influenza A(H1N1)pdm09 was the most frequently detected subtype in the subregion. In South-East Asia, detections of predominantly influenza B remained elevated due to continued detections reported in Malaysia.

COVID-19 positivity from sentinel surveillance continued to increase in the WHO Regions of the Americas (AMRO) and Western Pacific (WPRO). Activity increased to just over 30% in AMRO and 15% in WPRO and increased slightly in the European Region to 10%. Activity decreased and remained under 10% in the other regions. Globally, COVID-19 positivity from nonsentinel surveillance was around 10% or below, except in AMRO and WPRO, where activity maintained an increasing trend above 25%.