流感更新 第521期

Global Respiratory Virus Activity Weekly Update N°521 Summarizing data through Week 13, ending 30 March 2025 Summary Influenza •In the Northern hemisphere, influenza activity either continued to decline or remained stable in most countries. Slight increases were observed in a few countries in EasternAfrica, Southwest Europe, and Eastern Asia. Influenza positivity rates remained elevated (>10%) in North and Tropical South America (predominantly A viruses) andCentral America and the Caribbean (predominantly A(H1N1)pdm09), in Africa (predominantly A viruses with variations in subtypes across sub-regions), in Europe(predominantly A(H3N2) and B), in Western, Central and Southern Asia (predominantly A(H3N2) and B), South-East Asia (predominantly A(H1N1)pdm09 and B) andEastern Asia (predominantly A(H1N1)pdm09).•In the Southern hemisphere, influenza activity remained the same or decreased in all countries. Influenza positivity remained elevated in a few countries in Tropical SouthAmerica and Eastern Africa (predominantly A viruses), South-East Asia (predominantly A(H1N1)pdm09 and B viruses) and Oceania (predominantly A(H1N1)pdm09). SARS-CoV-2 •Globally, activity continued to be low across reporting countries except for a few countries in Temperate South America, Western Africa and Eastern Asia where positivityremained elevated (>10%). Influenza activity Additional information DataonrespiratoryvirussurveillanceareprovidedtoWHOthroughparticipa-tion or collaboration with the Global Influenza Surveillance and Response System (GISRS).Countries, areas, and territories (CATs) use a variety of approaches to monitor respiratoryvirus activity and data in this report may vary from surveillance reports posted elsewhere.Data in this report include virologic results from sentinel surveillance and other typesof systematically conducted virologic surveillance, depending on the CAT. Differencesin surveillance approaches limit comparison of percent positivity between CATs.Thesource of surveillance used in this report was determined in collaboration with WHORegional Offices and the reporting CAT. Analyses stratified by source of surveillance isavailable through RespiMart. Additional information on COVID-19 is reported on theWHO COVID-19 dashboard. TheproportionofspecimenstestingpositiveforinfluenzaorSARS-CoV-2wassmoothed over a 3-week period among CATs who reported testing at least 10 specimensfor 2 weeks of the 3-week period. The change in smoothed proportion of specimens testingpositive for each virus was calculated as the absolute difference from the smoothed valueduring the prior reporting week. ActivityissummarizedbygeographicalgroupingsofCATs.Thesegroupingswere used for their geographical description and do not imply similarity of respiratoryvirus transmission within each group. More information about the geographical groupingscan be found here. Specimens testing positive for influenza, by virus type and subtype Regional Reports Latest WHO regional surveillance reports: African | Americas | Eastern Mediterranean | European | South-East Asia | Western Pacific Summary was generated by the WHO Global Influenza Programme based on data last updated in RespiMart on April 06 2025 02:00:55 PM UTC