Dengue virus (DENV) is endemo-epidemic to hyper-endemic in French Guiana (FG). Several epidemics have occurred over the last 20 years, with co-circulation of different serotypes. FG has been experiencing since 2023 an unprecedented dengue epidemic, with co-circulation of the main DENV-2 and DENV-3 serotypes. We therefore studied retrospectively the DENV strains circulating in FG from 2000 until 2023-2024.

To achieve this goal, DENV samples from the collection of the National Research Center for Arboviruses French Guiana (NRCA-FG) were selected and sequenced using NGS (next generation sequencing) based on Oxford Nanopore Technologies (ONT).

Phylogenetic analysis showed i) DENV-3 FG sequences obtained all belonged to genotype III (GIII) with distinct lineages resulting from multiple Introductions ii) DENV-2 sequences in FG over the last 20 years showed that they belonged to two distinct DENV-2 genotypes, Asian American and Cosmopolitan with a succession of different lineages.

This study shows extinctions and reIntroductions of strains from globally circulating strains, rather than re-emergence of previously circulating strains. It also highlights the multiple Introductions driving to an important genetic diversity. Such diversity raises questions about the potential impact on patient immunity and long-term protection as well as the potential consequences on vaccine efficacy.