Weekly updates, Influenza Epidemiological Week 8 (3 March 2023)

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

Caribbean: Influenza activity remains elevated in the subregion, although presenting a decreasing trend, with A(H1N1)pdm09 predominance and A(H3N2) and B/Victoria co-circulation. Belize and Haiti reported increased influenza activity, and all seasonal subtypes co-circulated. SARS-CoV-2 activity was low in the subregion, except in Dominica and Suriname, where it was raised. RSV activity remained low in the subregion, except in Jamaica where increased RSV activity was reported. 

Central America: Influenza activity was moderate, with influenza B/Victoria virus predominance. Influenza A(H3N2) and A(H1N1)pdm09 co-circulated. Guatemala reported increased influenza activity with moderate levels of influenza B/Victoria circulation; SARI activity was low. Honduras reported increased influenza activity at moderate-intensity levels. SARS-CoV-2 percent positivity remains at moderate levels in the subregion, with high circulating levels in Costa Rica. RSV activity was low overall. 

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. SARS-CoV-2 activity was low overall. In the subregion, RSV activity was low. 

Brazil and Southern Cone: Influenza activity was at interseason levels; influenza A viruses were detected more frequently with co-circulation of B/Victoria and A(H1N1)pdm09. Paraguay reported increased influenza B (indeterminate lineage) activity at low-intensity levels with SARI and ILI low levels. SARS-CoV-2 activity was low, except in Brazil and Chile with moderate circulating levels. RSV activity remained low in the subregion except in in Brazil, where high levels were observed. 

Global: Globally, influenza activity decreased compared to the peak in late 2022. Influenza A viruses predominated with a slightly larger proportion of A(H1N1)pdm09. The proportion of influenza B virus detections increased during this reporting period. In Europe, influenza detections remained stable. Influenza positivity from sentinel sites increased in the most recent week, remaining above the epidemic threshold at the regional level. Out of 39 countries, 18 reported high or moderate intensity, and over half continued to report widespread activity. Influenza A and B viruses were detected similarly in both sentinel and non-sentinel surveillance. The proportion of influenza B viruses increased in recent weeks. Other indicators of influenza activity remained stable or decreased in most countries, while a few countries reported increases. In Central Asia, influenza activity decreased, while in Northern Africa, activity driven by all seasonal influenza subtypes was low and 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 was highest in eastern Africa but remained low overall, with detections of all seasonal influenza subtypes reported. 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, mainly due to continued detections 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 around 20% globally. The activity was about 25% in the WHO Region of the Americas, decreased to around 10% in the Western Pacific Region, and remained under 10% in the other regions. SARS-CoV-2 positivity from non-sentinel surveillance was reported at about 25% globally.