Week 12/2023 (20 March - 26 March 2023)

• The percentage of all sentinel primary care specimens from patients presenting with ILI or ARI symptoms that tested positive for an influenza virus decreased to 22% in week 12/2023 from 24% in the previous week and remaining above the epidemic threshold (10%). 
• 15 of 37 countries or areas reported medium intensity and 20 of 37 countries reported widespread activity indicating substantial seasonal influenza virus circulation across the Region.
• Of the 20 countries that reported sentinel primary care specimen influenza virus positivity above the 10% epidemic threshold, only Hungary reported activity above 40%.   
• Influenza type A and type B viruses were detected in sentinel and non-sentinel surveillance, with influenza type B predominating in both systems.  
• Hospitalized patients with confirmed influenza virus infection were reported from ICU (with higher proportions of type B viruses) and SARI surveillance (with higher proportions of type B viruses). Four countries or areas reported influenza virus positivity rates above 10% in SARI surveillance (Lithuania, Romania, Serbia and Ukraine).   

For week 12/2023, of 37 countries and areas reporting on intensity of influenza activity, 8 reported baseline-intensity (Azerbaijan, Belgium, Iceland, Netherlands, Republic of Moldova, United Kingdom (Northern Ireland), United Kingdom (Scotland) and Uzbekistan), 14 reported low-intensity (across the Region) and 15 reported medium-intensity (across the Region).

Of 37 countries and areas reporting on geographic spread of influenza viruses, 4 reported no activity (Azerbaijan, Kazakhstan, Kyrgyzstan and Uzbekistan), 5 reported sporadic spread (Belgium, Bulgaria, Israel, North Macedonia and United Kingdom (Northern Ireland)), 3 reported local spread (Belarus, Malta and Slovakia), 5 reported regional spread Lithuania, Republic of Moldova, Romania, Serbia and Kosovo (in accordance with UN Security Council Resolution 1244 (1999))) and 20 reported widespread activity (across the Region).

Please note: 

• Assessment of the intensity of activity indicator includes consideration of ILI or ARI rates. These ILI or ARI rates might be driven by respiratory infections other than influenza virus, including SARS-CoV-2, leading to observed increases in the absence of influenza virus detections.

• Assessment of intensity and geographic spread indicators includes consideration of sentinel and non-sentinel influenza virus detection data. Non-sentinel influenza virus detections, often higher, might translate into reporting of elevated geographic spread even in the absence of sentinel detections and/or low intensity of activity measured by ILI and ARI incidence.

* The administrative boundaries include spatial feature for Kosovo, this designation being without prejudice to position on status, and is in line with United Nations Security Council Resolution 1244 (1999) and the International Court of Justice Opinion on the Kosovo Declaration of Independence.