title: Epidemiological and molecular features of dengue virus type-1 in New Caledonia, South Pacific, 2001-2013.
abstract: BACKGROUND
  The epidemiology of dengue in the South Pacific has been characterized by transmission of a single dominant serotype for 3-5 years, with subsequent replacement by another serotype. From 2001 to 2008 only DENV-1 was reported in the Pacific. In 2008, DENV-4 emerged and quickly displaced DENV-1 in the Pacific, except in New Caledonia (NC) where DENV-1 and DENV-4 co-circulated in 2008-2009. During 2012-2013, another DENV-1 outbreak occurred in NC, the third DENV-1 outbreak in a decade. Given that dengue is a serotype-specific immunizing infection, the recurrent outbreaks of a single serotype within a 10-year period was unexpected.
  
  
  RESULTS
  This study aimed to inform this phenomenon by examining the phylogenetic characteristics of the DENV-1 viruses in NC and other Pacific islands between 2001 and 2013. As a result, we have demonstrated that NC experienced introductions of viruses from both the Pacific (genotype IV) and South-east Asia (genotype I). Moreover, whereas genotype IV and I were co-circulating at the beginning of 2012, we observed that from the second half of 2012, i.e. during the major DENV-1 outbreak, all analyzed viruses were genotype I suggesting that a genotype switch occurred.
  
  
  CONCLUSIONS
  Repeated outbreaks of the same dengue serotype, as observed in NC, is uncommon in the Pacific islands. Why the earlier DENV-1 outbreaks did not induce sufficient herd immunity is unclear, and likely multifactorial, but the robust vector control program may have played a role by limiting transmission and thus maintaining a large susceptible pool in the population.
authors.affiliation: URE- Dengue et autres Arboviroses, Institut Pasteur de Nouvelle-Calédonie, Réseau International des Instituts Pasteur, 98800 Nouméa, Nouvelle-Calédonie. mdupont@pasteur.nc.
authors.forename: Myrielle
authors.initials: M
authors.lastname: Dupont-Rouzeyrol
authors.forename: Maïté
authors.initials: M
authors.lastname: Aubry
authors.forename: Olivia
authors.initials: O
authors.lastname: O'Connor
authors.forename: Claudine
authors.initials: C
authors.lastname: Roche
authors.forename: Ann-Claire
authors.initials: AC
authors.lastname: Gourinat
authors.forename: Aurélie
authors.initials: A
authors.lastname: Guigon
authors.forename: Alyssa
authors.initials: A
authors.lastname: Pyke
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Grangeon
authors.forename: Eric
authors.initials: E
authors.lastname: Nilles
authors.forename: Suzanne
authors.initials: S
authors.lastname: Chanteau
authors.forename: John
authors.initials: J
authors.lastname: Aaskov
authors.forename: Van-Mai
authors.initials: VM
authors.lastname: Cao-Lormeau
mesh_terms: D016000:Cluster Analysis; D003715:Dengue / Q000453:epidemiology* / Q000821:virology*; D003716:Dengue Virus / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D009510:New Caledonia / Q000453:epidemiology; D010802:Phylogeny; D012367:RNA, Viral / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D012367:RNA, Viral