Influenza virus characterisation, March 2020
This is the fifth report for the 2019 2019–20 influenza season.
As of week 13/2020, 160 614 influenza detections across the WHO Europ ean Region ha have been reported; 73 % type A viruses, with A(H1N1 H1N1)pdm09 prevailing over A(H3N2) H3N2), and 27 % type B viruses, with 4 358 (98%) of 4 44 445 ascribed to a lineage being B/Victoria.
Since the February 20 2020 characterisation report report1, three shipments of influenza influenza-positive specimens from EU/EEA countries have been received at the London WHO CC, the Francis Crick Worldwide Influenza Centre (WIC). In total, 1 076 virus specimens, with collectio n dates after 31 August 2019 , have been received.
Of 86 A(H1N1)pdm09 test viruses from EU/EEA countries characterised antigenically since the last report, 78 (91 %) showed good reactivity with antiserum raised against the 20192019–20 va ccine virus, A/Brisbane/02/2018, with those viruses showing poor reactivity generally carrying amino acid substitutions (notably N156K) in the HA1 150 150-loop region. The 219 EU/EEA test viruses with collection dates from week 40/2019 genetically characterised at the WIC have fallen within subclades of clade 6B.1A: 191 6B.1A5A, 20 6B.1A5B, 1 6B.1A6 and 7 6B.1A7.
Since the last report, 55 A(H3N2) viruses have been characterised . T he majority of those viruse viruses showed reduced recognition by antiserum raised against the current vaccine virus, egg egg-propagated A/Kansas/14/2017 2017. Globally there have been approximately equal proportions of clade 3C.3a and subgroups 3C.2a1b+T131K and 3C.2a1b+T135K viruses detected. However, b ased on sequences available in GISAID from viruses detected since 1 February 2020 2020, subgroups 3c.2a1b+T135KA/B are prevalent in the USA while those of clade 3C.3a and subgroup 3C.2a1b+T131K dominate in Europe. In total, 295 viruses from EU/EEA countries have been characte characterised genetically at the WIC: 142 clade 3 C.3a, 106 3C.2a1b+T131K, 35 3C.2a1b+T135K T135K-A and 12 3C.2a1b+T135K T135K-B.
The great majority of the 62 B/Vi ctoriactoria-lineage viruses characterised in th is reporting period gave antigenic profiles characteris tic of subgroup 1A(Δ3)B viruses represented by B/Wa shington/02/2019 2019, the vaccine virus for the 2020 –21 northern hemisphere season. Viruses detected in EU/EEA countries during February and March 2020, based on sequences available in GISAID, have all fallen in the 1A(Δ3)B subgroup . In total, 172 EU/EEA viruses have been characterised genetically at the WIC: 159 subgroup 1A(Δ3)B and 13 subclade 1A(Δ2) Δ2).
Seasonal influenza is a preventable infectious disease with mostly respiratory symptoms. It is caused by influenza virus and is easily transmitted, predominantly via the droplet and contact routes and by indirect spread from respiratory secretions on hands etc.Read more
Flu News Europe: Weekly influenza updates
Weekly reports on influenza activity in Europe throughout the flu season are available as Flu News Europe reports and weekly infographic.Read more
Weekly threats reports (CDTR)
The ECDC Communicable disease threats reports are a weekly summary of all information gathered through epidemic intelligence activities regarding communicable diseases of concern to the EU. It also provides updates on the global situation and changes in the epidemiology of communicable diseases with potential to affect Europe. Diseases that are the focus of eradication efforts are also included.Read more