Emergence of dengue virus type 4 genotype IIA in Malaysia

This study reports the emergence of a new dengue virus type 4 (DENV-4) subgenotype IIA in Malaysia. Researchers isolated five DENV-4 viruses from dengue fever patients in Kuala Lumpur during 2001, a period when DENV-4 had been rarely detected for nearly a decade. By sequencing the envelope gene and performing phylogenetic analyses, the team identified that four isolates formed a distinct cluster with the Indonesian DENV-4 strain from 1973, suggesting a common ancestor. One isolate showed evidence of recombination between DENV-4 genotypes from different geographical origins and time periods. The remaining four isolates demonstrated recombination events involving both the ancestral Indonesian 1973 strain and one of the recently isolated viruses. These findings suggest that genetic recombination between different DENV-4 lineages contributed to the emergence of this new subgenotype. The authors conclude that recombination among dengue virus serotypes in natural populations can generate novel genotypes, particularly when multiple viral strains co-circulate in the same region.

Key findings

• A new DENV-4 subgenotype IIA emerged in Malaysia in 2001 after near-absence for 5 years, descended from Indonesian DENV-4 strain ID73 isolated in 1973
• Phylogenetic analysis of the envelope gene revealed one isolate had recombination signatures from DENV-4 genotypes I and II from different geographic origins
• Four other Malaysian isolates showed evidence of recent intra-serotypic recombination involving both the Indonesian 1973 strain and an independently isolated Malaysian virus
• Genetic recombination between different DENV-4 lineages contributed to the emergence of genotype IIA in Malaysia
• The study demonstrates that dengue virus recombination occurs naturally in populations with co-circulating multiple strains, generating novel genotypes