A subset of Member States monitor severe disease related to influenza virus infection by surveillance of 1) hospitalized laboratory-confirmed influenza cases in ICUs (n=12), or other wards (n=8), or 2) severe acute respiratory infections (SARI; n=16).
The majority of severe cases reported during the 2017–2018 season have been due to influenza type B and have occurred in persons above the age of 15 years. In laboratory-confirmed influenza cases in ICU, numbers of influenza type A infections were slightly higher than type B infections.
In laboratory-confirmed influenza cases reported in wards other than ICUs, influenza type B viruses were detected more frequently than influenza type A viruses, and more cases occurred among those older than 64 years compared with patients in the 15–64 years age group.
1.1) Hospitalized laboratory-confirmed influenza cases – Intensive care units (ICU)
Numbers of reported hospitalized laboratory-confirmed influenza cases in ICUs remained low during weeks 21–25/2018, with only the Czech Republic and Sweden reporting single cases.
For weeks 40/2017–20/2018, 12 countries reported laboratory-confirmed influenza cases admitted to either all ICUs in the country or a set of sentinel ICUs. Type A influenza viruses were detected in 53% and type B in 47% of cases in ICUs. Of 1 920 subtyped influenza A viruses, 58% were A(H1N1)pdm09 and 42% A(H3N2). Of 5 802 cases with known age, 44% were 15–64 years old and 48% were aged 65 years and older.
1.2) Hospitalized laboratory-confirmed influenza cases – other wards
For weeks 21–25/2018, the Czech Republic and Spain reported sporadic cases from other wards.
For weeks 40/2017–20/2018, 8 countries reported laboratory-confirmed hospitalized influenza cases in other wards. Influenza type B infections accounted for 61% of these cases and 57% of all cases were in patients aged 65 years and older.
2. SARI surveillance
For weeks 21–25/2018, 2 094 SARI cases were reported by 7 countries, most (43%) by Kazakhstan. 10 (3%) of the 350 specimens tested were positive for influenza viruses.
Sixteen countries, the majority being located in the eastern part of the Region, reported on SARI cases for weeks 40/2017–20/2018. Of SARI cases testing positive for influenza viruses over this period, 62% were infected with type B viruses. Of the 1 082 influenza type A infected cases for which subtyping was performed, 66% were infected by A(H1N1)pdm09 viruses.
For week 25/2018, the EuroMOMO project received data from 22 EU/EEA Member States or regions that were included in pooled analyses. Levels of all-cause mortality were at normal expected levels in all the participating countries.