Origins of Dengue Type 2 Viruses Associated with Increased Pathogenicity in the Americas

TLDR

The emergence of dengue hemorrhagic fever in the Americas has highlighted the need to identify virulent dengue virus strains, but limited in‑vitro models have made this difficult, so molecular epidemiology using E/NS1 gene sequences is used to trace evolutionary relationships and origins. The study recommends directing vaccination and control efforts toward reducing transmission of the identified virulent dengue type 2 genotypes. Phylogenetic analysis links the introduction of two Southeast Asian dengue type 2 genotypes to the rise of dengue hemorrhagic fever in the Americas, showing these strains displaced the native American genotype in at least four countries.

Abstract

The recent emergence and spread of dengue hemorrhagic fever in the Americas have been a major source of concern. Efforts to control this disease are dependent on understanding the pathogenicity of dengue viruses and their transmission dynamics. Pathogenicity studies have been hampered by the lack ofin vitroorin vivomodels of severe dengue disease. Alternatively, molecular epidemiologic studies which associate certain dengue virus genetic types with severe dengue outbreaks may point to strains with increased pathogenicity. The comparison of nucleotide sequences (240 bp) from the E/NS1 gene region of the dengue virus genome has been shown to reflect evolutionary relationships and geographic origins of dengue virus strains. This approach was used to demonstrate an association between the introduction of two distinct genotypes of dengue type 2 virus and the appearance of dengue hemorrhagic fever in the Americas. Phylogenetic analyses suggest that these genotypes originated in Southeast Asia and that they displaced the native, American genotype in at least four countries. Vaccination and other control efforts should therefore be directed at decreasing the transmission of these "virulent" genotypes.