Influenza in Europe, summary of the season 2017–18
Influenza activity started in week 47/2017 and returned to baseline levels in week 18/2018. In northern and south-western Europe (EU/EEA) , the activity started to increase between mid-December and early January, similar to the timing of the 2016–2017 season but earlier than in the previous five seasons.
The peak in activity was in early January in south-western Europe and in mid-February 2018 in northern Europe (EU/EEA). In some countries in Eastern Europe, influenza activity did not peak until mid- to late March.
The majority of influenza viruses detected were of type B, representing a higher level of circulation of influenza B viruses compared to recent seasons. Of all subtyped influenza B viruses detected in sentinel samples, 97% were B/Yamagata and 3% were B/Victoria viruses. Both influenza A subtypes, A(H3N2) and A(H1N1)pdm09 co-circulated in the region. Of all subtyped A viruses detected in sentinel samples, 38% were A(H3N2) viruses and 62% were A(H1N1)pdm09 viruses.
Influenza viruses circulated at high levels between weeks 51/2017 and 13/2018. This is longer than in recent seasons and may have contributed to the high severity of the 2017/18 season. Especially influenza B activity was detected for a longer period of the season and at a greater magnitude than in the previous seasons. Severe cases were observed in hospital settings due to B virus, but also due to A(H3N2) and A(H1N1)pdm09 viruses. Overall, the majority of severe cases were due to influenza virus type B infection and mostly were persons 40 years of age or older. Patients in intensive care units were mostly infected by influenza type A virus.
Overall, excess mortality from all causes was reported by the majority of 21 reporting countries during the influenza season and was mainly observed in people aged 65 years or older.
ECDC key updates
The main surveillance and virological outputs as well as articles on the vaccine vaccine effectiveness for the season is listed below.
All updates from ECDC and key partners on surveillance data and other developments for the influenza 2017-2018 season is also available via a Twitter moment. To reach the list of all updates, please go to Twitter or to the end of the page where we list all the key tweets for the season.
Seasonal influenza - Annual Epidemiological Report for 2017 - 2018
22 Oct 2018 - During the 2017–2018 season, 41 315 specimens from sentinel primary care providers were tested for influenza, 22% more than in the previous season; 49% of the specimens were positive for influenza virus (previous season: 40%).
Risk assessment for seasonal influenza, EU/EEA, 2017–2018
20 Dec 2017 - First detections indicated circulation of A(H3N2) and B/Yamagata viruses. As the former subtype dominated last season, a high proportion of the population should be protected. However, the emergence of variant strains cannot be excluded and this would increase the likelihood of severe outcomes in the elderly
Influenza Virus Characterisation reports, season 2017/18
The report provides an overview of the technical details of the circulating influenza viruses, such as antigenic and genetic properties, with a reference to the current vaccine strains. It also summaries the developments of the viruses since the last report, as well as the main developments for the ongoing season. Here you find the reports for the 2017/18 season.Read more
Dominant influenza A(H3N2) and B/Yamagata virus circulation in EU/EEA, 2016/17 and 2017/18 seasons, respectively
We use surveillance data to describe influenza A and B virus circulation over two consecutive seasons with excess all-cause mortality in Europe, especially in people aged 60 years and older. Influenza A(H3N2) virus dominated in 2016/17 and B/Yamagata in 2017/18. The latter season was prolonged with positivity rates above 50% among sentinel detections for at least 12 weeks. With a current west–east geographical spread, high influenza activity might still be expected in eastern Europe.Go to the article (Eurosurveillance 29 March 2018)
Interim 2017/18 influenza seasonal vaccine effectiveness: combined results from five European studies
Between September 2017 and February 2018, influenza A(H1N1)pdm09, A(H3N2) and B viruses (mainly B/Yamagata, not included in 2017/18 trivalent vaccines) co-circulated in Europe. Interim results from five European studies indicate that, in all age groups, 2017/18 influenza vaccine effectiveness was 25 to 52% against any influenza, 55 to 68% against influenza A(H1N1)pdm09, −42 to 7% against influenza A(H3N2) and 36 to 54% against influenza B.Go to the article (Eurosurveillance 1 March 2018)
Interim effectiveness of trivalent influenza vaccine in a season dominated by lineage mismatched influenza B, northern Spain, 2017/18
The 2017/18 interim estimate of trivalent influenza vaccine effectiveness (VE) was 39% (95% confidence interval: 20–54) in Navarre. Compared with individuals unvaccinated in the current and five previous seasons, VE against influenza B was 41% for current and any prior doses, 67% for current vaccination only, and 22% for any prior doses, and 43%, 51% and 54%, respectively against influenza A(H3N2). This suggests moderate VE despite predominance of lineage mismatched influenza B.Go to the article (Eurosurveillance 15 Feb 2018)
Early season co-circulation of influenza A(H3N2) and B(Yamagata): interim estimates of 2017/18 vaccine effectiveness, Canada, January 2018
Using a test-negative design, we assessed interim vaccine effectiveness (VE) for the 2017/18 epidemic of co-circulating influenza A(H3N2) and B(Yamagata) viruses. Adjusted VE for influenza A(H3N2), driven by a predominant subgroup of clade 3C.2a viruses with T131K + R142K + R261Q substitutions, was low at 17% (95% confidence interval (CI): −14 to 40). Adjusted VE for influenza B was higher at 55% (95% CI: 38 to 68) despite prominent use of trivalent vaccine containing lineage-mismatched influenza B(Victoria) antigen, suggesting cross-lineage protection.Go to the article (1 Feb 2018)