Weekly updates, Influenza Epidemiological Week 4 (3 February 2023)

North America: Influenza activity was low overall in the subregion. Influenza A(H3N2) continued predominating with the co-circulation of A(H1N1)pdm09 and B/Victoria. The SARS-CoV-2 activity increased, while RSV activity decreased. In Canada, influenza activity continues to decrease. In Mexico, influenza activity was within expected levels for this time of year, with severity indicators at low levels. In the United States, influenza activity continued to decrease, with the percentage of deaths due to pneumonia, influenza, and COVID-19 above the average of previous seasons and declining. RSV activity was low overall.

Caribbean: Influenza activity increased in the subregion with A(H1N1)pdm09 predominance and B/Victoria co-circulation. In addition, influenza activity was elevated in Belize, French Guiana, and Haiti. The SARS-CoV-2 activity was moderate and increasing, while RSV activity was at baseline levels.

Central America: Influenza activity was moderate, with influenza A and B virus detections and A(H3N2) 5 predominance. Guatemala and Honduras reported increased influenza activity, with influenza A(H3N2) and A(H1N1)pdm09 predominance, respectively. Overall, SARS-CoV-2 percent positivity decreased in the subregion. RSV activity remained raised
in Guatemala.

Andean: Influenza activity was low, with the predominance of influenza B/Victoria and co-circulation of influenza A(H3N2) and A(H1N1)pdm09. In Bolivia, influenza activity was increased, while in Ecuador, influenza activity was low. SARS-CoV-2 activity was elevated in Colombia and Ecuador but decreasing. In the subregion, RSV activity was low overall.

Brazil and Southern Cone: Influenza activity was very low, with influenza B viruses more frequently detected and co-circulation of B/Victoria and A(H1N1)pdm09. SARS-CoV-2 activity was moderate in some countries and decreasing. However, Brazil and Chile reported increased RSV activity.

Global: Influenza activity decreased. Influenza A viruses predominated with a slightly larger proportion of A(H1N1)pdm09 viruses detected among the subtyped influenza A viruses. In Europe, overall influenza activity continued to decrease, but influenza positivity from sentinel sites remained above the epidemic threshold at the regional level. Influenza A viruses predominated with A(H1N1)pdm09, accounting for most subtyped influenza viruses from primary care sentinel sites but with regional differences. Many countries reported high or moderate intensity and most reported widespread activity. Other indicators of influenza activity decreased in most countries, while a few reported increases. In Central Asia, influenza activity decreased overall but remained somewhat elevated, with influenza A(H1N1)pdm09 viruses predominant. In Northern Africa, influenza activity continued to decline, with all seasonal influenza subtypes detected. In Western Asia, influenza activity decreased overall with all seasonal influenza subtypes detected, though increased activity was reported in some countries. In East Asia, influenza activity of predominantly influenza A(H3N2) viruses remained low overall though detections continued to be reported at elevated levels in Mongolia and the Republic of Korea. In tropical Africa, influenza activity was highest in eastern Africa but remained low overall, with detections of all seasonal influenza subtypes reported. In Southern Asia, influenza activity slightly, with all seasonal influenza subtypes detected in similar proportions. In South-East Asia, detections of predominantly influenza B remained elevated due to continued detections reported in Malaysia. In the temperate zones of the southern hemisphere, influenza activity remained at the inter-seasonal level.

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