Figure 2.

Maximum-likelihood phylogenetic tree of 4467 DENV-1 envelope (E) gene sequences (1485 nucleotides). The midpoint rooted phylogenetic tree, which includes 12 new sequences from viremic travelers returning from PNG to Australia, was inferred using FastTree and the generalized time-reversible (GTR) nucleotide substitution model.³⁸ Percentage Shimodaira-Hasegawa-like local support values are shown for key nodes estimated from 1000 resamples. To emphasize positions of sequences from PNG and accommodate the very large sample size, PNG sequences are colored red among collapsed phylogenetic clusters and geographical locations of closely related sequences are shown. The inset phylogenetic tree within genotype IV depicts the established, endemic PNG lineage. A closely related lineage containing DENV-1 2002–2003 sequences from the Pacific is shown colored blue. Horizontal branch lengths are proportional to the bar representing the number of nucleotide substitutions/site.