Partial nucleotide sequencing and molecular evolution of epidemic causing dengue 2 strains

To study the genetic variability and to detect evolutionary changes and mov ement of dengue 2 (DEN-2) strains, nucleotide sequencing of the envelope pr otein gene and the nonstructural protein 1 gene junction was performed for 9 isolates from the 1996 Delhi epidemic and 1 isolate from the 1967 Delhi e pidemic. The epidemic strains had a divergence of 10%-11% from the 1967 str ains, but were quite similar to DEN-2 isolates from Seychelles, Somalia, an d Torres Strait, In addition, the sequence data were compared to the protot ype DEN-2 strain, New Guinea C, and other published DEN-2 sequences from di fferent parts of the world. The phylogenetic analysis by the Molecular Evol utionary Genetics Analysis program suggests that the 1996 Delhi isolates of DEN-2 were genotype IV. The 1967 isolate was similar to a 1957 isolate of DEN-2, P9-122, from India, and was classified as genotype V. This study ind icates that earlier DEN-2 strains of genotype V have been replaced by genot ype IV.