Phylogenetic tree of murine retroviral DNA sequences from CFS and healthy subjects. Results are displayed for one CFS Positive Control Subject (G018), five CFS Subjects (G026, G028, G035, G071 and G091) and two Healthy Subjects (G046 & G053). For these subjects, the first four letters/digits are subject anonymous identifier numbers while the last four letters/digits identifies replicates. Public MLV (blue text) and top mouse clone hits, which are also retroviral homologs (purple text), are included in the tree reconstruction. The position of the previously reported, PCR XMRV contaminant sequence (HM990971) is indicated . The tree was reconstructed by neighbor-joining (NJ) method using DNA distance matrices of core conserved nucleotides (see Methods). Asterisks (“*”) indicate those nodes supported 70% or greater in 1000 bootstrap replicate NJ trees and 0.95 Bayesian posterior probability while nodes with numbers had high NJ bootstrap values only. Scale bar represents 0.1 expected nucleotide substitutions per site.