Fig. 1.

Cluster analysis of monkeypox viruses based on relative synonymous codon usage (RSCU) bias. (A) Heat map of RSCU, excluding tryptophan codon UGG, start codon AUG, stop codons UAA, UGA and UAG. (1)–(20) are monkeypox viruses; (21) is a fowlpox virus, as an outgroup. (B) Phylogenetic tree constructed by using the Euclidean distance method with the Neighbor-Joining (NJ) model. Three distinct clusters are marked with red, blue and green respectively. Bar represents 0.10 Euclidean distance. (C) Geographical distribution of 20 monkeypox virus strains. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)