深圳市3例由输入性病例引发的本地登革热病例溯源调查

Molecular tracing of pathogen of three local dengue fever cases originated from imported case in Shenzhen in 2017

目的对深圳市2017年本地感染登革热病例进行病原溯源研究。方法对3例本地感染登革热病例开展流行病学调查,采集患者血清进行登革病毒IgM与IgG抗体、NS1抗原和核酸检测。用C6/36细胞进行病毒分离,用荧光RT-PCR方法对其进行型别鉴定。采用RT-PCR方法扩增病毒E基因后,进行序列测定构建进化树。结果实验室检测3例本地病例登革病毒核酸及NS1抗原均为阳性。分离到的2株登革毒株与1株马来西亚输入病例分离株E基因序列同源性为100%,为登革病毒2型Ⅳ亚型,与马来西亚2014年流行株TM280亲缘关系最近,核苷酸和氨基酸同源性分别为99.7%和99.8%,病毒株来源于马来西亚的可能性较大。结论现场流行病学资料和实验室分子遗传学分析均提示,深圳市2017年3例本地感染登革热病例可能是由马来西亚旅游归国的输入性病例引发的继发病例。

Objective To trace the origin of pathogens of three local dengue fever cases in Shenzhen in 2017. Methods The epidemiological surveys were conducted and the serum samples were collected from suspected dengue fever patients to detect IgM and IgG against dengue virus, NS1 antigens and nucleic acids. Dengue fever virus was isolated with C6/36 cell line and typing of virus was performed by real-time RT-PCR. The E genes of the virus strains were sequenced after amplification by RT-PCR for the construction of phylogenetic tree. Results The serum samples of three local patients were positive for dengue virus nucleic acids and NS1 antigens. Two dengue virus strains from local cases and one strain from an imported case from Malaysia showed 100% similarity in E gene sequences. The isolated virus strains were confirmed to be dengue virus type-2 (subtype Ⅳ). The stains were the closest to the predominant strain TM280 in 2014 in Malaysia and the similarities of nucleotide sequences and amino acid sequences were 99.7% and 99.8%, respectively, indicating that virus strains might originated from Malaysia. Conclusions Both on-site epidemiological data and laboratory molecular genetic analysis suggested that three local dengue fever cases in Shenzhen in 2017 may be the secondary cases caused by the imported case returned from travelling in Malaysia.