Figure 1: Genetic characterization of viruses collected in season 2019-2020 (log2 HI titre reciprocal = HIU, hemagglutination inhibiting units log2). (A) A(H1N1)pdm09 viruses, (B) A/(H3N2) viruses); (C) B/Victoria viruses; (D) B/Yamagata viruses. Hemagglutination inhibition was performed using ferret antisera against A/Brisbane/02/2018 [ A(H1N1)pdm09 ], A/Kansas/14/2017 [ A/(H3N2) ], B/Colorado/6/2017 (B/Victoria) and B/Phuket/3073/2013 (B/Yamagata). Note that there was a good coverages of vaccine viruses in the influenza season 2019-2020 with the exception of N156K viruses.
Each rhombus represents a virus. Dark blue column, variation of the positive control (vaccine virus) = 1 log2; light blue column, accepted tolerance in antigenic variation against vaccine viruses = 2 log2; dark red column, viruses with N156K substitution in HA.