Abstract: Objective To analyze the epidemiological and etiological characteristics of imported dengue fever cases in Kunming City in 2019 for evidences in planning prevention and control measures for this infection. Methods The epidemiological information was collected from the imported dengue fever cases in Kunming City in 2019 according to the National Dengue Surveillance Program in China. Serum samples were obtained from part of the imported dengue fever cases reported between January and June of 2019, and subjected to serotyping of the dengue virus (DENV) by RT-PCR. In addition, E gene sequence of the virus was amplified for phylogenetic analysis. Results A total of 400 imported cases were reported in Kunming in 2019, in which 297 (74.25%) were imported from foreign countries such as Cambodia (187 cases), Myanmar (38 cases) and Laos (28 cases). Ninety-nine cases (24.75%) were from mainland China, and most of them (93 cases) were from Xishuangbanna of Yunnan Province. The cases were reported all year round, and peaked from May to October of the year. The male to female ratio was 2.01∶1. The cases were distributed in every age group, yet most were young adults aged from 20 to 50 years (84.25%). The occupation of the reported cases was associated with house-workers and currently unemployed (19.5%), traders (14%), government staffs (13%), famers (11.5%) and workers (10.75%). Between January and June of 2019, a total of 60 aliquots of serum samples were collected from the imported dengue fever cases that were from Cambodia (n=49), Laos (n=1), Myanmar (n=3), Vietnam (n=3), Thailand (n=1) and African countries (n=3). Of the 60 samples, 29 and 5 were respectively positive for DENV-1 and DENV-2. The cases imported from Cambodia were involved in DENV-1 (n=28) and DENV-2 (n=4), and DENV-2 and DENV-1 were seen in one case from Vietnam and another one from Thailand. Eight E gene sequences of DENV were amplified from 34 samples, 6 of which were DENV-1 from Cambodia, and 2 of which were DENV-2 from and Thailand. Phylogenetic tree analysis showed that 6 strains of DENV-1 belonged to genotype Ⅰ, and nucleotide sequence identities among the 6 sequences were 96.63% -100.00%. Of six sequences, one (imported from Thailand) was highly homologous with the epidemic strained identified in 2019 in Thailand, and the other 5 sequences (imported from Cambodia) had the highest homology with the strain reported in Guangdong (imported from Cambodia in 2019) and in Nanchang in 2019 (imported from Cambodia and Laos). DENV-2 sequences amplified from two strains of the cases imported from Cambodia belonged to Asian Ⅰ genotype, with a nucleotide sequence identity being 99.73%. Both strains were in high homology with those reported in Guangdong imported from Cambodia in 2019. Conclusion In 2019, most dengue cases in Kunming City were imported from Southeast Asian countries, and the imported dengue virus strains were highly homologous with the strains epidemic in and imported from Southeast Asian countries. The results suggest that it is necessary to improve early detection and report of the imported cases in order to prevent local outbreaks caused by imported cases. 

Key words: Dengue fever, Imported cases, Epidemiological characteristics, E gene, Phylogenetic analysis, Kunming City