Abstract
BackgroundInfection by dengue virus (DENV) is a major public health concern in hundreds of tropical and subtropical countries. French Polynesia (FP) regularly experiences epidemics that initiate, or are consecutive to, DENV circulation in other South Pacific Island Countries (SPICs). In January 2009, after a decade of serotype 1 (DENV-1) circulation, the first cases of DENV-4 infection were reported in FP. Two months later a new epidemic emerged, occurring about 20 years after the previous circulation of DENV-4 in FP. In this study, we investigated the epidemiological and molecular characteristics of the introduction, spread and genetic microevolution of DENV-4 in FP.Methodology/Principal FindingsEpidemiological data suggested that recent transmission of DENV-4 in FP started in the Leeward Islands and this serotype quickly displaced DENV-1 throughout FP. Phylogenetic analyses of the nucleotide sequences of the envelope (E) gene of 64 DENV-4 strains collected in FP in the 1980s and in 2009–2010, and some additional strains from other SPICs showed that DENV-4 strains from the SPICs were distributed into genotypes IIa and IIb. Recent FP strains were distributed into two clusters, each comprising viruses from other but distinct SPICs, suggesting that emergence of DENV-4 in FP in 2009 resulted from multiple introductions. Otherwise, we observed that almost all strains collected in the SPICs in the 1980s exhibit an amino acid (aa) substitution V287I within domain I of the E protein, and all recent South Pacific strains exhibit a T365I substitution within domain III.Conclusions/SignificanceThis study confirmed the cyclic re-emergence and displacement of DENV serotypes in FP. Otherwise, our results showed that specific aa substitutions on the E protein were present on all DENV-4 strains circulating in SPICs. These substitutions probably acquired and subsequently conserved could reflect a founder effect to be associated with epidemiological, geographical, eco-biological and social specificities in SPICs.
Highlights
Almost all tropical and subtropical regions of the world are concerned by the risk of dengue
Our results showed that specific aa substitutions on the E protein were present on all dengue virus (DENV)-4 strains circulating in South Pacific Island Countries (SPICs)
The patients were members from the same family recently returned from New Caledonia (NC) where a DENV-4 outbreak had recently commenced concomitantly with DENV-1 transmission
Summary
Almost all tropical and subtropical regions of the world are concerned by the risk of dengue. Dengue virus (DENV) causes more than 50 million infections, 500 000 hospitalizations and 12 500 deaths, mostly children [1]. Based on the sequence of the envelope gene (E), each serotype may be divided into distinct phylogenetic clusters or genotypes [4]. Both epidemiological observations and in vitro studies suggest that some genotypes may have different epidemic potential [5,6,7]. Infection by dengue virus (DENV) is a major public health concern in hundreds of tropical and subtropical countries. Two months later a new epidemic emerged, occurring about 20 years after the previous circulation of DENV-4 in FP. We investigated the epidemiological and molecular characteristics of the introduction, spread and genetic microevolution of DENV-4 in FP
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