Phylogenetic tree of DENV-1 and DENV-2. The phylogenetic tree was constructed by the maximum likelihood method with a Kimura 2 parameter model using MEGA 5.0 software. Bootstrap values were set for 1000 repetitions. The black dots denote strains from the local population, and the black triangles denote strains from foreign travelers. The sequences of reference strains were derived from GenBank (www.ncbi.nlm.nih.gov).