Weekly updates, Influenza. Epidemiological Weeks 50-51 (29 December 2022)

North America: Influenza activity was moderate, although increasing 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 above expected levels. In Mexico, influenza activity continued above expected levels, with SARI cases at low-intensity levels. Influenza activity seems to have reached a plateau at moderate-intensity levels in theUnited States, with influenza-associated cumulative hospitalization rates higher than the highest cumulative in-season hospitalization rate observed in week 51 (2010-21). Elevated RSV activity continued but with a decreasing trend.

Caribbean: Influenza activity was moderate across the subregion with A(H3N2) virus predominance and B/Victoria co-circulation. SARS-CoV-2 activity remained low overall.BelizeandHaitihave shown increased influenza activity at low-intensity levels, while Guadeloupe and Martinique registered increased RSV activity. 5

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

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

Brazil and Southern Cone: Influenza activity was moderate, 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) predominance. In Chile, influenza A(H3N2) predominated, showing a decreasing trend. 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.