深圳市2014年登革热流行病学和病原学特征研究

Epidemiological and etiological characteristics of dengue fever in Shenzhen in 2014

目的研究深圳市2014年登革热疫情的流行病学特征，分析流行毒株的分子进化特征，为今后登革热的防控提供科学指导。方法采用描述性流行病学方法分析2014年深圳市登革热疫情，分别采用胶体金免疫层析法和荧光PCR检测疑似登革热患者血清中的特异性IgM、IgG抗体和病毒核酸，并用C6/36细胞对急性期血清进行病毒分离，采用荧光PCR方法对其进行型别鉴定。同时扩增病毒E基因后进行序列测定，并与不同国家和地区的登革热毒株进行同源性比较和进化树分析。结果2014年深圳市累计报告登革热病例454例，以本地病例为主（占76.21%），输入病例以东南亚国家及周边城市为主（占23.79%）。发病高峰为9—11月（占97.14%）。发病人群以20～50岁青壮年人群为主，占病例总数的76.73%，男女比为1.43∶1。对332份病毒核酸阳性标本进行分型检测，共检出270例，型别以1型登革病毒（DENV-1）为主（占87.41%），其次为DENV-2（占8.89%）。进化分析发现深圳地区流行的DENV-1分布在两个分支上，其一为基因Ⅰ亚型，与深圳市2010年首次本地暴发疫情流行株同源性较高；其二为基因Ⅴ亚型，为深圳市首次报道。DENV-2核苷酸序列的差异相对较小，均为基因Ⅳ亚型。结论2014年深圳市报告登革热病例达到历年高峰，其流行具有输入病例与本地传播并存特点，主要是DENV-1流行，同时今年新出现DENV-2型病例明显增多，推测主要流行株由东南亚国家及周边城市输入，是否具有地方性登革热流行趋势还需进一步研究。

Objective To investigate the epidemiological characteristics of dengue fever in Shenzhen city in 2014 and to analyze the evolutional characteristics of the epidemic dengue virus （DENV） strains in order to provide scientific guidelines for the prevention and control of dengue fever. Methods Descriptive epidemiological analysis was used to analyze the prevalence of dengue fever in Shenzhen city in 2014. Immunochromatography and real-time PCR were performed to detect the specific antibodies （ IgM and IgG） and DENV nucleic acids in serum samples collected from suspected cases of dengue fever. Serum samples collected from the patients at early stage of dengue fever were used to infect the C6/36 cell line for further isolation of DENV strains. The types of isolated DENV strains were determined by using real-time PCR. E genes of the isolated DENV strains were amplified by RT-PCR and then sequenced. DNAStar and Clustslx （1.83） softwares were used to analyze the homology between DENV strains isolated in Shenzhen and other areas. A phylogenetic tree based on the sequences of E genes of Shenzhen strains and other sequences of DENV reference strains downloaded from GenBank was constructed for further analysis. Results A total of 454 cases of dengue fever were reported in Shenzhen in 2014 with a male to female ratio of 1.43 ： 1. Local patients accounted for 76.21% and the rest 23.79% were imported cases mainly from Southeast Asian and surrounding cities. There were 441 cases reported from September to November, accounting for 97.14% of all reported cases. Most of the infected subjects were aged 20 to 50, accounting for 76.73%. Of the 270 samples positive for DENV nucleic acids, strains of DENV-1, DENV-2, DENV-3 and DENV-4 accounted for 87.41% , 8. 89% , 0.37% and 2.22% , respectively. The phylogenetie tree analysis revealed that the DENV-1 strains belonged to two genotypes, which were genotype Ⅰ and genotype Ⅴ. The DENV strains of genotype Ⅰ were highly similar to the epidemic strain isolated in Shenzhen in 2010 and the genotype Ⅴ strains were first reported in Shenzhen. The homology analysis of the nucleotides of E genes showed that minor differences in the nucleotide sequences were found between DENV-2 strains. All of the DENV-2 strains belonged to the genotype Ⅳ as indicated by the phylogenic tree. Conclusion There were 454 cases of dengue fever （including both local and imported cases） reported in Shenzhen city in 2014, reaching an all-time high. DENV-1 was the predominant pathogen in combination with an increased infection of DENV-2. This study indicated that the prevalent DENV strains might be imported from Southeast countries and neighboring cities. Further researches should be conducted to analyze whether dengue fever is endemic in Shenzhen City.