title: Emergence of an independent lineage of dengue virus type 1 (DENV-1) and its co-circulation with predominant DENV-3 during the 2006 dengue fever outbreak in Delhi.
abstract: OBJECTIVE
  The sudden emergence of dengue virus type 1 (DENV-1) and its co-circulation with predominant DENV-3 was the hallmark of the 2006 dengue fever outbreak in Delhi. Viruses that circulated between 1996 and 2005 in the City have been well characterized, but the genomic diversity in 2006 strains is not known. The present study was undertaken to reveal the emerging molecular genotype(s) and evolutionary trend of the viruses responsible for the dengue fever outbreak in Delhi during 2006.
  
  
  METHODS
  The CprM gene junction of the DENV isolates from the 2006 Delhi dengue fever outbreak were subjected to nucleotide sequencing. Comparative phylogenetic analysis was done using DENV-1 and DENV-3 sequences retrieved from the global database.
  
  
  RESULTS
  Multiple sequence alignment revealed only substitutions, with no insertions or deletions. A dendrogram indicated emergence of a distinct lineage of DENV-1 (having similarity with the Comoros/Singapore 1993 and Delhi 1982 strains, but quite different from the Delhi 2005 lineage) and microevolution of the pre-circulating DENV-3. These findings point towards the circulation of two independent lineages of DENV-1 in Delhi during 2005 and 2006.
  
  
  CONCLUSIONS
  It is feared that the introduction of an independent lineage of the outbreak-associated strain of DENV-1 and its co-circulation with the deeply-rooted strain of DENV-3 in Delhi may result in yet another, possibly more severe outbreak in the near future.
authors.affiliation: Division of Biochemistry and Biotechnology, National Institute of Communicable Diseases (NICD), 22 Shamnath Marg, Delhi - 110054, India.
authors.forename: Himani
authors.initials: H
authors.lastname: Kukreti
authors.forename: Artee
authors.initials: A
authors.lastname: Chaudhary
authors.forename: R S
authors.initials: RS
authors.lastname: Rautela
authors.forename: Ranjana
authors.initials: R
authors.lastname: Anand
authors.forename: Veena
authors.initials: V
authors.lastname: Mittal
authors.forename: Mala
authors.initials: M
authors.lastname: Chhabra
authors.forename: D
authors.initials: D
authors.lastname: Bhattacharya
authors.forename: Shiv
authors.initials: S
authors.lastname: Lal
authors.forename: Arvind
authors.initials: A
authors.lastname: Rai
mesh_terms: D001483:Base Sequence; D021821:Communicable Diseases, Emerging; D003715:Dengue / Q000145:classification / Q000453:epidemiology* / Q000821:virology*; D003716:Dengue Virus / Q000145:classification / Q000235:genetics*; D004196:Disease Outbreaks; D005838:Genotype; D006801:Humans; D007194:India / Q000453:epidemiology; D010802:Phylogeny