Fig. 2

Phylogenetic tree of available genomic sequences of the DENV-2 and DENV-1 E genes, for which clinical samples were collected in Taiwan during the DF outbreak in 2015. a An original phylogenetic tree of 82 genomic sequences of the DENV-2 E gene obtained from GenBank. Two DENV-1 sequences were used as an outgroup. The DENV-2 sequences from which the clinical samples were collected from autochthonous cases were phylogenetically close to the sequences from the clinical samples that were collected from Indonesia. A virus with the abbreviation TN in its name was isolated from clinical samples collected in Tainan city. A virus with the abbreviation KH was isolated from clinical samples collected in Kaohsiung city. The two letters “Tw” at the end of the virus name mean that the sequence was imported into Taiwan from the country in the name. The phylogenetic analysis was inferred by using the maximum likelihood and fits of 484 different nucleotide substitution models, and the results suggested that TIM2 + F + I + G4 was the best-fitting model with the lowest Bayesian information criterion (BIC) scores of 14,173.117 among the 484 models tested. The tree topology was automatically computed to estimate maximum-likelihood values. The optimal log-likelihood for this computation was –6,612.703. There was a total of 1377 positions in the final dataset. Blue squares indicate cases from Indonesia whose evolutionary relationship is close to autochthonous Taiwanese DF cases. The box around a grouping of sequences highlights the autochthonous cases without travel history, except for the two cases from Indonesia with a small blue square on the left. b An original phylogenetic tree of 159 genomic sequences of the DENV-1 E gene obtained from GenBank. Four DENV-2 sequences were used as an outgroup. The phylogenetic analysis was inferred by using the maximum likelihood and fits of 484 different nucleotide substitution models, and the results suggested TN + F + I + I + R2 as the best-fitting model with the lowest BIC scores of 20,599.992 among the 484 models tested. The tree topology was automatically computed to estimate the maximum-likelihood values. The optimal log-likelihood for this computation was –9,229.897. There was a total of 1,485 positions in the final dataset. Blue squares indicate cases from Indonesia whose evolutionary relationship is close to autochthonous Taiwanese DF cases