title: Phylogenetic analysis of dengue viruses isolated from imported dengue patients: possible aid for determining the countries where infections occurred.
abstract: BACKGROUND
  Molecular epidemiology of dengue viruses in endemic countries have been reported, but few were reported on the imported dengue cases among travelers. We analyzed dengue viruses isolated from imported dengue cases in Japan who were infected while traveling in endemic regions of the world.
  
  
  METHODS
  We sequenced the complete envelope (E) gene of 33 dengue virus strains isolated from patients returning from Asia, Oceania, South Pacific islands, and South America to Japan where no domestic dengue virus infection occurs. We then performed phylogenetic analysis to define the geographic origin of isolated viruses. Moreover, we compared the genomes of isolated dengue viruses with those of the strains already deposited in the GenBank database.
  
  
  RESULTS
  The isolates are clustered into expected genotypes, confirming that the viruses originated from the visited countries. When patients visited more than one country during a single trip, the countries where the infection occurred were also determined for four of the six patients. There were three isolates, which were different genotypes from those previously isolated in visited countries.
  
  
  CONCLUSIONS
  The study demonstrates that many dengue virus strains are introduced into Japan and that phylogenic analysis of isolated dengue viruses is a unique technique to determine the countries where infection occurred. Travelers carry viruses and provide important and unique information for clarifying dengue virus trait and its dissemination.
authors.affiliation: Department of Virology 1, National Institute of Infectious Disease, Tokyo, Japan.
authors.forename: Mikako
authors.initials: M
authors.lastname: Ito
authors.forename: Ken-Ichiro
authors.initials: K
authors.lastname: Yamada
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Takasaki
authors.forename: Basu
authors.initials: B
authors.lastname: Pandey
authors.forename: Reiko
authors.initials: R
authors.lastname: Nerome
authors.forename: Shigeru
authors.initials: S
authors.lastname: Tajima
authors.forename: Kouichi
authors.initials: K
authors.lastname: Morita
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kurane
mesh_terms: D001208:Asia; D018076:DNA, Complementary / Q000032:analysis; D003715:Dengue / Q000145:classification / Q000235:genetics* / Q000635:transmission*; D003716:Dengue Virus / Q000145:classification* / Q000235:genetics*; D018562:Disease Transmission, Infectious / Q000145:classification*; D005838:Genotype; D006801:Humans; D007564:Japan; D010802:Phylogeny; D012367:RNA, Viral / Q000032:analysis*; D013020:South America; D014195:Travel
chemical_list: D018076:DNA, Complementary; D012367:RNA, Viral