Complete Genome Sequence Analysis of a Dengue Case Co-Infected with Type I and Type II Imported into Jiaxing in 2023

In 2023, one case of coinfection with type I and type II dengue virus of imported origin was first reported in Jiaxing city. Therefore, we analysed the results of the molecular tracing analysis of this case. We collected serum samples for whole-genome amplification and sequencing and further analysed the whole-genome sequence for homology analysis, evolutionary tree analysis, and protein amino acid mutation site analysis. The results revealed that the JX202301 DENV-1 sequence had the highest homology with the epidemic strains in Guangdong (PP563909, PP563875, PP563840, and PP563879) in 2023, with nucleotide homology ranging from 99.5 to 99.8% and amino acid homology of 100%. The JX202301 DENV-2 sequence had the highest homology with the epidemic strains of 2019 Thailand (MZ636805, MZ636802, MZ636803, MW512454, and MW512419), with nucleotide homology ranging from 98.4 to 99.2% and amino acid homology of 99.7%. By analysing the amino acid mutation sites, we found that, compared with the corresponding reference strains and the epidemic strains in the same branch, there were 52 amino acid difference sites in the viral coding region of the DENV-1 sequence and 51 amino acid difference sites in the viral coding region of the DENV-2 sequence, which were mainly concentrated in the NS1 and NS5 region of the nonstructural proteins. In this study, we described for the first time the genome-wide sequence, genetic variation, and phylogenetic analysis of imported DENV-1 and DENV-2 mixed cases in Jiaxing city. These results provide a scientific basis for dengue fever outbreak surveillance, viral evolution studies, and prevention and control strategy development in Jiaxing city.