Phylogenetic tree from the Bayesian MCMC (MrBayes) analysis.

The 50% majority rule consensus was constructed and posterior probabilities are indicated by asterisks in nodes (black * upper 0.85 and red * upper 0.95). MRCA including the vast of majority sequences analyzed (black ♦) and MRCA from the cluster viruses (red ♦) are marked. Branch lengths represent the mean value observed for that branch among the post-burning sampled trees. The branch colors identified nucleotide sequences origin: black correspond to ancient sequences from North-America (before 1991) and from Europe (before 1995), blue are Spanish sequences (from 1989 and 2005) and red Spanish cluster sequences (from 2004–2005, except As7 which was from 1989). Green sequences are from elite suppressors [54] and yellow sequences from elite controller patients [54]. Gray lines are D subtype sequences used as outgroup in the bottom of the tree.