Molecular characterization of the envelope gene of dengue virus type 3 newly isolated in Guangzhou, China, during 2009-2010.

BACKGROUND

After an absence of 29 years, dengue virus type 3 (DENV-3) re-emerged in Guangzhou in 2009 and again in 2010. However, the geographical route by which the virus entered the city, and how it has changed genetically, remain unclear. Therefore, we carried out a comprehensive investigation into the molecular characteristics of the DENV-3 involved.

METHODS

The envelope (E) genes of viruses isolated from dengue patients during the 2009-2010 epidemics were sequenced and compared with previously published E gene sequences of global representative DENV-3 strains available in GenBank, including isolates circulating in other provinces of China.

RESULTS

A total of 13 isolates (seven from 2009 and six from 2010) were obtained from human serum samples. Phylogenetic analysis revealed that the isolates were grouped into three genotypes (I, III, and V) and then two clades within genotype III (genotype I from Indonesia, genotype III clade A from Côte d'Ivoire, genotype III clade B from Tanzania, and genotype V from Philippines). In addition, there were 1.3-9.0% and 0.5-3.9% differences in the nucleic and deduced amino acid sequences between the 2009 and 2010 strains, respectively.

CONCLUSIONS

The DENV-3 viruses from the period 2009-2010 were not from the continuous spread of an epidemic strain or the re-emergence of the 2009 strains in the 2-year period. The introduction of different DENV-3 genotypes following more than one geographical route was an important contributing factor to the 2009-2010 dengue epidemics in Guangzhou.