The epidemic of Dengue virus type-2 Cosmopolitan genotype on Reunion Island relates to its active circulation in the Southwestern Indian Ocean neighboring islands

Abstract

Reunion Island is currently experiencing an epidemic caused by Dengue virus type-2 (DENV-2) resulting in over 6,763 cases from austral summer 2017 to winter 2018. Phylogenetic analyses on two non-imported cases of dengue infection from Reunion Island highlight a regional circulation of DENV-2 Cosmopolitan lineage 1 virus on both Reunion Island and the Seychelles.

Keywords: Virology.

Fig. 1

Phylogenetic analysis of the envelope E-gene sequence of DENV-2 from Reunion Island, March–May 2018. Bayesian inference computation was performed with a set of 110 corresponding sequences retrieved from GenBank, all being representative of the different sub-genotypes reported for the DENV-2. Two DENV-1 E-gene sequences were included as outgroup. A red star indicates the topological location in the tree for the sequences from Reunion Island. Posterior probabilities are depicted in an orange square at the node level. The branches of the tree are colored according their genotyping origin.

Fig. 2

Phylodynamic history of the DENV-2 sequences to estimate the introduction dates for the regional circulation – Maximum clade credibility tree of Dengue-2 E-gene sequences. The phylogenetic relationships and temporal evolutionary history have been estimated based on molecular clock analysis. Branch lengths are temporally scaled, and the x-axis presents a time scale (years before present - y.b.p). In the left panel zoom of the main tree, date estimates at the node level are depicted in a green square given in year by past (y.b.p.). The red squares numbered 1, 2 and 3 represent, respectively, the t_MRCA of the putative introduction of DENV-2 on the Seychelles, on the Seychelles-Reunion Island, and at the regional level.