Genotyping and molecular tracing of dengue virus in Zhaoqing, Guangdong, 2014-2015

Objective To understand the origins and genotypes of dengue virus circulating in Zhaoqing in Guangdong province from 2014 to 2015. Methods Blood samples were collected from clinical dengue fever cases in Zhaoqing from 2014 to 2015 and detected by using real-time RT-PCR. The positive samples in PCR were used for virus isolation. The E genes from isolated strains were amplified and sequenced, the phylogenetic tree was constructed and homology analysis were performed with Mega 5.1 software. Results In 409 samples detected in real-time RT-PCR, 147 were positive, in which 139 of 144 were positive for DENV 1 in 2014 and 2 of 3 were positive for DENV 3 in 2015, respectively. A total of 22 strains of dengue virus were isolated and identified. Phylogenetic analysis showed that the 20 strains of DENV 1 isolated in 2014 belonged to genotype Ⅰ and Ⅲ, sharing 99.40%-100.00% and 99.20%-100.00% homology with the strains isolated in Guangzhou and Foshan during 2013-2014, respectively, but low homology with the strains isolated in Singapore, Thailand, Malaysia and Indonesia. The 2 DENV 3 strains isolated in 2015 were identified as genotype Ⅲ, sharing 98.20%-99.70% homology with the strains isolated in Singapore and Indonesia in recent years. Conclusion DENV 1 belonging to genotype Ⅰ and Ⅲ was the pathogen causing dengue fever outbreak in Zhaoqing in 2014, which might spread from Guangzhou and Foshan, while the DENV 3 detected in sporadic infections belonged to genotype Ⅲ, which might spread from Foshan in 2015. All the strains might originated from Southeast Asian countries, such as Singapore and Indonesia.