Weekly influenza update, week 48, December 2017

Period: 27 Nov 2017 - 03 Dec 2017

ECDC and WHO/Europe publish weekly influenza surveillance data in the report Flu News Europe.


  • Influenza activity across Europe remained at low levels.
  • Of the individuals sampled, on presenting with ILI or ARI to sentinel primary healthcare sites, 8.8% tested positive for influenza viruses, a higher proportion than the previous week (7%).
  • Data from 16 countries or regions reporting to the EuroMOMO project indicated that all-cause excess mortality was within normal ranges for this time of year.

2017/18 season overview 

  • Since week 40/2017, a relatively low number of influenza viruses have been detected in sentinel and non-sentinel specimens.
  • From sentinel sources, a slightly higher proportion of type B viruses compared to type A viruses has been detected. Approximately equal proportions of A(H1N1)pdm09 and A(H3N2) viruses have been detected.
  • For type B viruses from both sentinel and non-sentinel sources, B/Yamagata lineage viruses have greatly outnumbered those of the B/Victoria lineage.
  • While low in number, of the A(H3N2) viruses genetically characterized 61% belonged to clade 3C.2a, the vaccine virus clade, as described in the WHO recommendations for vaccine composition for the northern hemisphere 2017–2018, and 39% to clade 3C.2a1 of which the viruses are antigenically similar to those of clade 3C.2a.