Objective To understand the whole-genome sequence characteristics of the imported dengue virus serotype 1 (DENV-1) in Dali Bai autonomous prefecture (Dali), Yunnan province, in 2023.

Methods The serum samples of suspected dengue fever cases were collected for the detection of nucleic acid by real-time fluorescence quantitative PCR. The positive samples were subjected to whole genome capture, library construction and sequencing of dengue virus. The whole genome sequence and genotyping of the virus were obtained by using bioinformatics analysis software. The homology analysis, nucleotide and amino acid sequence identity analysis, amino acid site difference analysis on the whole genome sequence were further performed by the construction of a phylogenetic tree.

Results The whole genome sequences of 17 strains of dengue virus were obtained from the serum of dengue fever cases in Dali imported from Xishuangbanna and Lincang, all of which belonged to gene type I of DENV-1. Phylogenetic tree analysis indicated that the 17 strains had the closest genetic relationship with 2023 Guangzhou strain (PP563875.1) from Guangdong province, China, and 2023 Xishuangbanna strain (PV162554.1), and showed high homology with 2023 Thailand strain (PV344274.1). The average nucleotide and amino acid identity levels among the 17 strains were 99.89% - 99.95% and 99.72% - 99.91%, respectively, and the average nucleotide and amino acid identity levels with the reference sequences were 98.84% - 99.92% and 96.81% - 99.86%, respectively. Amino acid locus variations were observed in capsid protein, precursor membrane protein, envelope protein, non-structural protein 1, non-structural protein 2A, non-structural protein 4B, and non-structural protein 5. Notably, the amino acid sequence of Q0057W0149 strain was identical to that of 2023 Guangzhou strain (PP563875.1).

Conclusion The DENV-1 isolated from the imported dengue fever case in Dali in 2023 was homologous to the strains isolated from Guangzhou and Xishuangbanna, China during the same period, and it had relatively close genetic distance and relatively high identity with the strains isolated in Thailand in 2023, 2017 and 2015. The study results suggested that the imported dengue virus strains might belong to DENV-1 lineage originated from Thailand.