Weekly influenza update, week 47, November 2017

Summary

• Influenza activity across Europe remained at low levels.
• Of the individuals sampled on presenting with ILI or ARI to sentinel primary healthcare sites, 6.3% tested positive for influenza viruses, which is higher than the previous week (3.7%).
• Data from 21 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, the proportion of B virus is slightly more important compared to A viruses.
• For type B viruses from both sources, B/Yamagata lineage viruses have greatly outnumbered those of the B/Victoria lineage.
• While low in number (n=35), over 59% of the A(H3N2) viruses genetically characterized belonged to clade 3C.2a, the vaccine virus clade, as described in the WHO recommendations for vaccine composition for the northern hemisphere 2017–18.