Figure 1
From: Long-term adaptation of the influenza A virus by escaping cytotoxic T-cell recognition
CTL epitope evolution in the influenza A virus.
Antigenic map of 295 representative influenza A viruses spanning the period 1932–2015 (□H1N1, △H2N2, ○H3N2, 
pH1N1) based on 134 CTL epitopes. The H3N2 subtype has evolved extensively over the period 1968–2015, while the H2N2 and H3N2 viruses circulating in the late 1960s are antigenically close. Recent avian viruses are superimposed independently onto the antigenic map (
H5N1, 
H7N9 and 
H9N2), using the 134 CTL epitopes of human IAV origin. The map is constructed using multi-dimensional scaling (MDS) based on Jaccard distances, explaining 93% of the antigenic distances (Methods). Scale bar denotes expected differences in the number of epitopes; colours indicate collection year of the virus.
