Diversity of serotypes and genotypes and molecular tracing of dengue viruses isolated from dengue fever cases in Yunnan

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Objective To understand the serotypes, genotypes and transmission source of dengue viruses(DENV) isolated in Yunnan from 2013 to 2015. Methods Viral RNA was extracted from serum samples of dengue fever(DF) cases at the acute stage in Yunnan, then the gene fragments of envelope protein(E) region were amplified by RT-PCR. The homology and phylogenetic analysis was made on the nucleotide and deduced amino acid sequences by bioinformatics softwares including Clustal X, DNAStar and MEGA5. Results Viral nucleic acid detection and sequencing indicated that 40 E genes of DENV were obtained. The serotypes and genotypes of DENV were revealed by homology and phylogenetic analysis based on E genes of DENV. Fifteen virus strains belonged to DENV serotype 1(DENV-1), of these, 14(11 from Ruili, 1 from Lincang and 2 from Kunming) were genotype I(G-I), 1 from Kunming was G-V. Twenty-two virus strains belonged to DENV serotype 2(DENV-2), of these, 10 from Ruili were G-I and 12 from Xishuangbanna were G-IV. Two virus strains belonged to DENV serotype 3(DENV-3) and G-II. One virus strain belonged to DENV serotype 4(DENV-4) and G-I. All detected DENV genotypes were mainly predominant in Southeast Asia. All the 40 Yunnan DENV strains shared high homology with the DENV strains in Southeast Asia countries. Conclusions Four serotypes and multiple genotypes of DENV had been co-circulating in Yunnan from 2013 to 2015. The DENV transmitted from Southeast Asia countries was the main cause of DF in Yunnan. It is necessary to strengthen the surveillance and management on the imported cases of DF in Yunnan. Key words: Dengue virus; E gene; Serotype; Genotype; Phylogenetic analysis