Dengue fever, a
mosquito-borne
viral infection, causes significant
morbidity and has become endemic in the Indian subcontinent.
Virus strains currently circulating in many parts of the country are not well studied at the molecular level. In the present study, genetic characterization of
virus strains from a
dengue outbreak that occurred in and around a
tertiary care hospital in Ernakulam, Kerala in the year 2008 has been reported. By
reverse transcription polymerase chain reaction (RT-PCR), 37 out of 75 (49.3%) clinically suspected cases were positive for
dengue viral RNA. Among these, 21 (56.8%) samples showed concurrent
infection with multiple
serotypes of the
virus. Majority of the combined
infections were caused by
dengue serotype 2 and 3.
Co-infections with type 1 and 2 in two
patients, and type 1, 2 and 3 in one
patient were also observed. The core-pre-
Membrane (CprM) junction
nucleotide sequencing and
phylogenetic analysis revealed that the type 1
strains were related to the viral
strains reported from Delhi-2001 and Gwalior-2002
dengue outbreaks, while the type 2
strains were related to the
strains from Gwalior-2001
epidemic. Sequences of type 3
strains did not show clear relation to any of the previous Indian isolates, and in the
phylogenetic analysis, they formed a distinct lineage within the Indian type 3
strains. This study indicates hyperendemicity of
dengue in the region with the presence of multiple
serotypes and high rates of
co-infection, and local genomic evolution of the viral
strains involved in this outbreak.