Continued persistence of a single genotype of dengue virus type-3 (DENV-3) in Delhi, India since its re-emergence over the last decade.

BACKGROUND/PURPOSE: The re-emergence of an epidemic strain of dengue virus type-3 (DENV-3) in Delhi in 2003 and its persistence in subsequent years marked a changing trend in dengue virus circulation in this part of India. Its evolving phylogeny over the past decade has not been studied in detail as yet. METHODS: Reverse transcription polymerase chain reaction and sequencing of the CprM gene junction of DENV-3 from different outbreaks since 2003 was carried out. Thirty CprM DENV-3 sequences from this study were compared with 46 other previously reported CprM DENV-3 sequences from India and other countries. Multiple sequence alignment and phylogenetic trees were constructed to determine the extent of genetic heterogeneity and trace the phylogeny of DENV-3. RESULTS: Thirty CprM DENV-3 sequences (Accession numbers AY706096–99, DQ645945–52, EU181201–14, and EU846234–36) were submitted to GenBank. The CprM junction was found to be AT rich (approximately 53%). Nucleotide sequence alignment revealed only nucleotide substitutions. Phylogenetic analysis indicated sustained evolution of a distinct Indian lineage of DENV-3 genotype III in Delhi. CONCLUSION: Active circulation of DENV-3 genotype III over the last decade in Delhi was evident and worrying. This genotype has been implicated in several outbreaks in South-East Asia and other parts of the world.