Molecular epidemiology of dengue virus types 1 and 2 in Ruili, Yunnan, 2014

Objective To understand the serotype of dengue virus and molecular epidemiologic characteristics of an outbreak of dengue fever in Ruili, a city in Sino-Myanmar border area, in Yunnan province in 2014. Methods The incidence data of dengue fever in Ruili were collected. Serum samples from the dengue fever cases in acute phase were collect to detect the viral nucleic acid by using RT-PCR assay. The phylogenetic tree was constructed according to the nucleotide sequence of C/PreMgene fragments of dengue viruses. Results A total of 292 cases of dengue fever were laboratory confirmed in Ruili from June to December, 2014, in which 139 were indigenous cases(47.77%), 153 were imported cases (52.23%), i.e., 152 from Myanmar and 1 from Guangzhou of China. The local incidence of dengue fever was 77.69/lakh. The disease mainly occurred in urban area, Jiegao development zone and Mengmao town of Ruili. The results of viral nucleic acid detection and sequencing indicated that the nucleotide sequences of C/PreM region of 65 virus strains were obtained, including 40 local strains and 25 imported strains from Myanmar. The phylogenetic tree indicated that 53 strains belonged to serotype 1 (31 local strains and 22 imported strains from Myanmar), 11 strains belonged to serotype 2 (9 local strains and 2 imported strains from Myanmar) and 1 strain belonged to serotype 4 (from Myanmar). All the 65 strains shared high homology with the strains from Southeast Asia countries. Conclusion In the outbreak of dengue fever in Ruili in 2014, both indigenous cases and imported cases were detected. Dengue virus serotype 1 and 2 circulated in both Mujie of Myanmar and Ruili of China in 2014.The transmission of dengue fever from Mujie of Myanmar to Ruili of China was the main cause of local dengue fever epidemic.