For week 6/2017, of the 15 countries that conduct sentinel surveillance on severe acute respiratory infection (SARI), 13 reported data and 6 of the 9 countries that conduct surveillance on hospitalized laboratory-confirmed influenza cases reported data.
Of 1 374 SARI cases reported, 218 were tested for influenza virus and 52 (24%) were positive: two A unsubtyped, three A(H1N1)pdm09, 31 A(H3N2) and 16 type B viruses. Since week 40/2016, 23 903 SARI cases have been reported from 15 countries with 6 373 tested for influenza virus, of which 2 353 (37%) were positive: 1 992 (85%) were type A and 361 15%) type B viruses. Of the influenza A viruses, 1 872 (94%) were A(H3N2), 4 (<1%) were A(H1N1)pdm09 and 116 (6%) were not subtyped.
For week 6/2017, of nine countries that conduct surveillance on hospitalized laboratory-confirmed influenza cases in intensive care units (ICU) or other wards, the Czech Republic, France, Ireland, Romania, Spain, Sweden and the United Kingdom reported a total of 221 cases, 141 in ICU and 80 in other wards. Of 141 patients admitted to ICU in week 6/2017, a decrease from 54 cases in the previous week, 99 were infected with unsubtyped A viruses, 40 with A(H3N2), and two with type B viruses. From other wards, 80 cases were reported in week 6/2017 (a decrease of 37 cases compared to previous week) by the Czech Republic, Ireland, Romania and Spain. Of these, 46 were infected with unsubtyped A viruses and 34 with A(H3N2) viruses.
Since week 40/2016, the Czech Republic, Ireland, Romania, Slovakia and Spain have reported 3 070 laboratory-confirmed influenza cases admitted to non-ICU wards; 1 772 infected with unsubtyped A viruses, 1 278 with A(H3N2), four with A(H1N1)pdm09, and 16 with type B influenza viruses. In total, 2 929 cases have been admitted to ICU; 1 789 infected with unsubtyped influenza A viruses, 983 with A(H3N2), 111 with A(H1N1)pdm09, and 46 with type B influenza viruses.
Since the start of the season, most of the hospitalized laboratory-confirmed influenza cases reported have occurred in people aged 65 years or older (Fig. 4). Information on patient age and influenza virus (sub)type was available for 2 096 cases admitted to ICU; the majority (65%) of cases (n=1 362) were aged ≥65 years, 635 (30%) were aged 15–64 years and 99 (5%) were aged under 15 years. A(H3N2) viruses predominated and accounted for 721 cases, 97% of the subtyped influenza A viruses in cases admitted to ICUs. 635 deaths have been reported, 359 from ICUs and 276 from other wards (338 infected with unsubtyped A viruses, 289 with A(H3N2), three with A(H1N1)pdm09 and five with type B viruses) with 515 (81%) cases among patients aged ≥65 years.
Figure. Distribution of virus (sub)type in influenza-confirmed cases admitted to ICU by age-group, cumulatively
Data from 19 countries or regions reporting to the EuroMOMO project were received for week 6/2017 and included in the pooled analyses of excess all-cause mortality. The majority of reporting countries across the European region continue to see a marked increase in all-cause excess mortality among the elderly aged 65 years or older. In addition, a substantial increase has been observed in the 15–64 years age group. This is probably due to the dominance of influenza A(H3N2) virus circulation.