A subset of countries and areas monitor severe disease related to influenza virus infection by surveillance of

1) hospitalized laboratory-confirmed influenza cases in ICUs or other wards, or

2) severe acute respiratory infections (SARI).

1.1) Hospitalized laboratory-confirmed influenza cases – ICUs  

For week 10/2023, 18 laboratory-confirmed influenza cases were reported from ICU wards (in Czechia (n=1), France (n=6) and Sweden (n=11)). Both influenza type B (n=67%) and type A viruses (n=33%) were detected. No viruses were ascribed to a subtype or lineage.

Since week 40/2022, more influenza type A (n=2 647, 91%) than type B (n=246, 9%) viruses were detected (in Czechia (5%), France (30%), Ireland (5%), Sweden (8%) and United Kingdom (England) (52%)). Of 482 subtyped influenza A viruses, 53% were A(H3) and 47% were A(H1)pdm09. No influenza B viruses were ascribed to a lineage. Of 1 380 cases with known age, 643 were 15-64 years old, 572 were 65 years and older, 102 were 0-4 years old and 63 were 5-14 years old.

1.2) Hospitalized laboratory-confirmed influenza cases – other wards

For week 10/2023, 7 laboratory-confirmed influenza A cases without subtype were reported from other wards (in Czechia). Of these cases, 6 were caused by type A viruses and 1 by a type B virus. Three influenza type A viruses were subtyped, 2 were A(H3) and 1 was A(H1)pdm09.

Since week 40/2022, 3 804 influenza type A viruses and 176 influenza type B viruses were detected (in Czechia (4%) and Ireland (96%)). Of 396 subtyped influenza A viruses, 63% (n=251) were A(H1)pdm09 and 37% (n=145) A(H3). The 3 980 cases with known age fell in 4 age groups: 1 708 were 65 years and older, 1 372 were 15-64 years old, 499 were 0-4 years old and 401 were 5-14 years old.