Severity

The 11 countries that reported data on sentinel surveillance of severe acute respiratory infections (SARI) reported a total of 423 SARI cases for week 19/2017. Among these cases 88 respiratory specimens were collected, 6 (7%) of which, from Armenia (n=2), Kosovo (n=1) and the Russian Federation (n=3), tested positive for influenza viruses.

Since week 40/2016, 16 countries have reported 39 272 SARI cases. Of these 10 700 were tested for influenza viruses, 3 566 (33%) of which were positive: 2 706 (76%) were type A and 860 (24%) type B viruses. Of the influenza A viruses, 2 493 (92%) were A(H3N2), 7 (<1%) were A(H1N1)pdm09 and 206 (8%) were not subtyped.

For week 19/2017, of 9 countries that conduct surveillance of hospitalized laboratory-confirmed influenza cases, 2 countries each reported one ICU case.

Since week 40/2016, the 9 countries reported 3 708 cases that have been admitted to ICU; 3 585 (97%) were infected with influenza type A viruses (2 136 unsubtyped, 1 320 A(H3N2) and 129 A(H1N1)pdm09) and 123 with type B viruses.

Since week 40/2016, 5 countries have reported 3 776 laboratory-confirmed influenza cases admitted to non-ICU wards; 3 703 (98%) were infected with influenza type A viruses (2 059 unsubtyped, 1 636 A(H3N2), 8 A(H1N1)pdm09), and 73 were infected with type B influenza viruses.

Since the start of the season, information on patient age and influenza virus (sub)types was available for 2 604 cases admitted to ICU; the majority of cases (64%; n=1 667) were aged ≥65 years, 795 (31%) were aged 15–64 years and 142 (5%) were aged under 15 years (Fig).

In total, 939 deaths among hospitalized laboratory-confirmed influenza cases have been reported, 536 from ICUs and 403 from non-ICU wards, with 765 (81%) of all deaths occurring in patients aged 65 years or older. Of all fatal cases, 930 (99%) were due to influenza A with 457 (99%) of those subtyped being A(H3N2) viruses.

Fig. Distribution of virus (sub)type in influenza-confirmed cases admitted to ICU by age-group, cumulatively

Mortality Monitoring

Data from 20 countries or regions reporting to the Euromomo project were received for week 19/2017 and included in the pooled analyses of excess all-cause mortality.  

The majority of participating European countries experienced a marked excess in all-cause mortality between the beginning of January 2017 and the end of February 2017, in particular among the elderly (those aged 65 years and above). Mortality levels have since decreased to expected levels. This season’s excess mortality coincided with circulation of influenza A(H3N2) viruses, which usually leads to increased mortality among the elderly.