Parts of the phylogenetic tree inferred for subtype B sequences sampled across Europe. Monophyletic groups of sequences sampled from A. Austria (purple), B. Portugal (cyan), C. Luxembourg (orange) and D. Poland (green). E. Part of the tree showing the geographical dispersal of HIV-1 subtype B sequences. Branches are shown in different colours by country of origin as described in the legend. Branches are not drawn to scale.