Epidemiological and molecular features of dengue virus type-1 in New Caledonia, South Pacific, 2001–2013
1 URE- Dengue et autres Arboviroses, Institut Pasteur de Nouvelle-Calédonie, Réseau International des Instituts Pasteur, 98800 Nouméa, Nouvelle-Calédonie
2 Institut Louis Malardé, 98713 Papeete Tahiti, Polynésie Française
3 Institut Pasteur de Nouvelle-Calédonie, Réseau International des Instituts Pasteur, 98800 Nouméa, Nouvelle-Calédonie
4 Queensland Health Forensic and Scientific Services, QLD 4108 Coopers Plains, Australia
5 Direction des Affaires Sanitaires et Sociales, 98800 Nouméa, Nouvelle-Calédonie
6 Pacific Technical Support Division, World Health Organization, PO BOX 113, Suva, Fiji
7 Queensland University of Technology, Brisbane QLD 4001, Australia
Virology Journal 2014, 11:61 doi:10.1186/1743-422X-11-61Published: 31 March 2014
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.
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.
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.