Global Respiratory Virus Activity: Weekly Update No. 572

GLOBAL INFLUENZA SURVEILLANCE AND RESPONSE SYSTEM (GISRS) Co-circulationInfluenza SUMMARY Globally, influenza positivity was below 10% in week 13 2026. SARS-CoV-2 activity remained low overall. Influenza predominated and positivity wasbelow 10% in the northern hemisphere temperate and subtropical areas and in tropical areas. In the southern hemisphere temperate and subtropical areas, Globally, influenza detections continued to decline in week 13 and influenza B viruses were predominant among influenza detections. [Figure 2] In the northern hemisphere, influenza percent positivity was elevated (>10%) in single countries in North America, Northern and Eastern Africa andin countries in Northern and Eastern Europe, and Southern, Eastern and South-East Asia. Percent positivity was over 30% in countries in CentralAmerica and the Caribbean and in a single country in Western Africa. Small increases in activity were observed in single countries in Central America In the southern hemisphere, influenza activity remained low overall although elevated positivity (>10%) was reported in single countries in Temperateand Tropical South America, Southern Africa and South-East Asia. Percent positivity was over 30% in one country in Tropical South America. Small In the zones with elevated positivity, influenza A(H3N2) was predominant in Central America and the Caribbean, Tropical and Temperate SouthAmerica, Eastern Europe and Southern Asia. Influenza A(H1N1)pdm09 was predominant in Northern Europe and Southern Africa. Influenza B was qSARS-CoV-2Globally, SARS-CoV-2 positivity remained stable and low. A small increase was reported in one country in Central America and the Caribbean.[Figures 7 and 8] qRespiratory Syncytial Virus (RSV)Globally, RSV positivity remained stable and low, with a few countries reporting elevated positivity (>10%) in Tropical South America, Europe and asingle country in Northern Africa. Percent positivity was over 30% in a single country in Eastern Africa. Small increases in activity were reported in a qSeverity assessmentThe severity assessments here are reported from countries, areas and territories. Assessments for transmissibility can be reported based on syndromicparameters and/or influenza-specific parameters. In the northern hemisphere temperate and subtropical areas, influenza-specific transmissibility wasreported as low in a single country; transmissibility using syndromic data was reported as below seasonal threshold and moderate in single countries. Co-circulation of influenza and SARS-CoV-2 1b) Weekly numbers of influenza andSARS-CoV-2 virus specimens tested and 1d) Weekly numbers of influenza andSARS-CoV-2 virus specimens tested and Influenza SARS-CoV-2 Respiratory syncytial virus Severity assessment Additional information Data and methods The data presented in this report originates from virologic surveillance conducted by countries, areas, and territories (CATs) and submitted to WHO FluNet through participation orcollaboration with the Global Influenza Surveillance and Response System (GISRS). These CATs employ diverse methodologies to monitor respiratory virus activity, which may resultin variations between this report and other surveillance summaries published elsewhere. To assess trends, the proportion of specimens tested positive for influenza or SARS-CoV-2 was smoothed over a 3-weeks period. This analysis includes only countries that tested 10 ormore specimens in at least two of the three weeks. Weekly changes in the smoothed positivity rate for each virus were calculated as absolute differences from the previous week. These The influenza transmission zones map is based on data aggregated over a 3-weeks period, moving backward from the current week until a minimum threshold of 100 tested samples isreached within each influenza transmission zone. Pie charts are displayed on the map only if the total percent positivity in a influenza transmission zones map is 20% or higher. All trend analyses are based on ISO 8601 calendar week numbering. Activity summaries are organized by geographical groupings of CATs. These groupings are intended solely for geographic reference and do not imply uniformity in respiratory virustransmission patterns within each group. It is important to note that specimens tested for influenza, SARS-CoV-2, and RSV may not originate from the same sample sources within surveillance systems.Severity assessments:The severity assessments here are reported from countries, areas and territories.WHO’s Pandemic influenza severity assessment (PISA): a WHO guide to assess the severityof influenza in seasonal epidemics and pandemics, 2nd ed outlines the methods for which countries, areas and territories can derive these severity assessments. Assessments for Countries, areas and territories may not provide assessments year-round. The assessments may be revised over time if there is retrospective/delayed reporting or updating of previouslyreported data. Th