Severity

Of the 12 countries that conduct sentinel surveillance of severe acute respiratory infection (SARI) for week 15/2017, 9 countries reported 1,728 SARI cases. Among these cases, 197 respiratory specimens were collected, 44 (22%) of which tested positive for influenza viruses in 7 countries (Armenia, Belarus, Georgia, Kazakhstan, Republic of Moldova, Russian Federation and Ukraine).

Since week 40/2016, a total of 16 countries have reported 36 815 SARI cases. Of these 10 162 were tested for influenza viruses, 3 505 (34%) of which were positive: 2 704 (77%) were type A and 801 (23%) type B viruses. Of the influenza A viruses, 2 491 (92%) were A(H3N2), 6 (<1%) were A(H1N1)pdm09 and 207 (8%) were not subtyped.

For week 15/2017, of 9 countries that conduct surveillance of hospitalized laboratory-confirmed influenza cases, 2 countries (Czech Republic and Sweden) reported 3 cases, 2 in intensive care units (ICU) and 1 in other wards. Of the patients admitted to ICU, 1 was infected with influenza type A virus and 1 with influenza B. The other ward case was infected with A(H3N2).

Since week 40/2016, 9 countries reported a total of 3 641 cases that have been admitted to ICU; 3 550 (98%) were infected with influenza type A viruses (2 112 - unsubtyped, 1 311 - A(H3N2) and 127 - A(H1N1)pdm09) and 91 with type B viruses.

Since week 40/2016, 5 countries have reported 3 736 laboratory-confirmed influenza cases admitted to non-ICU wards; 3 691 (99%) were infected with influenza type A viruses (2 062 - unsubtyped, 1 622 - A(H3N2), 7 - A(H1N1)pdm09), and 45 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 2 585 cases admitted to ICU; the majority of cases (64%; n=1 654) were aged ≥65 years, 791 (31%) were aged 15–64 years and 140 (5%) were aged under 15 years (Fig). In total, 921 deaths have been reported, 523 from ICUs and 398 from other wards, with 749 (81%) of the patients aged 65 years or older. Of all fatal cases, 912 (99%) were due to influenza A with 449 (>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 15/2017 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 December 2016 and 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), which usually leads to increased mortality among the elderly.