广西壮族自治区2014年登革热暴发疫情流行病学特征和病原溯源

Study of epidemiological characteristics and viral sources of dengue fever outbreak in Guangxi Zhuang Autonomous Region, 2014

目的 了解2014年广西壮族自治区（广西）登革热暴发疫情流行病学特征和病原来源。方法 描述疫情时间、人群和地区分布特征，应用ELISA方法检测血清标本中的登革病毒（DENV）NS1抗原，用RT-PCR方法对NS1抗原阳性标本进行DENV血清分型、E基因序列扩增和测定，分析E基因序列一致性和进化关系。结果 2014年9-12月广西暴发DENV-1和DENV-2引起的本地登革热疫情，报告登革热病例854例（实验室诊断病例712例，临床诊断病例142例），79.63%（680/854）病例集中在2014年9月22日至10月21日；所有病例均为典型登革热病例，无重症和死亡病例； 83.61%（714/854）病例年龄为15-59岁，46.60%（398/854）病例职业为干部和商业服务；疫情主要发生在南宁市和梧州市，E基因进化分析表明，中国南宁市本地病例分离株属DENV-1基因Ⅰ型，与新加坡分离毒株（SG EHI D1/529Y13）一致性为100.00%；梧州市本地病例分离株与广东省分离毒株（D14005）同源性最高，属DENV-2 Cosmopolitan基因型。结论 2014年广西登革热暴发疫情可能由输入性病例或媒介引起，中国南宁市本地暴发疫情病原为DENV-1，可能来源于新加坡；梧州市本地暴发疫情病原为DENV-2，可能从广东省输入。应加强输入性登革热病例监测和早期检测，做好蚊媒监测，提高疑似登革热病例诊断意识，以有效防控登革热疫情。

Objective To understand the epidemiological characteristics and viral sources of dengue fever outbreak in Guangxi Zhuang Autonomous Region （Guangxi） in 2014. Methods A combined analysis of epidemiological characteristics and genetic characteristics were performed in this study. The time, population and area distributions of the cases were analyzed. Serum samples were collected from dengue fever cases to detect NS1 antigen by using commercial ELISA kits according to the guideline of the manufacture. RT-PCR assay was conducted to detect dengue virus in NS1 positive samples. Phylogenetic tree based on E gene sequence of dengue virus were further analyzed. Results During September-December 2014, an outbreak of dengue fever caused by dengue virus type 1 and 2 occurred in Guangxi, a total of 854 cases were reported without death, including 712 laboratory confirmed cases and 142 clinical diagnosed cases, in which 79.63% （680/854） occurred during 22 September-21 October 2014. All the cases had typical dengue fever symptoms. Most cases occurred in Nanning and Wuzhou, in which 83.61% （714/854） were in age group 15-59 years; 46.60% （398/854） were staff or people engaged in commercial service. A total 526 serum samples were tested for dengue virus serotype by RT-PCR assay. Among 414 positive samples, 345 were positive for dengue virus type 1 （DENV-1） and 69 were positive for dengue virus type 2 （DENV-2）, no DENV-3 and DENV-4 were detected. The results of phylogenetic analysis of E gene sequence indicated that the sequences of 99.12%（113/114） of DENV-1 strains in Nanning in China shared 100.00% homology with the isolate （SG EHI D1/529Y13） from Singapore in 2013, which belonged to the genotypeⅠ; All the DENV-2 isolates from Wuzhou shared 99.80% homology with the isolate （D14005） from Guangdong province, which belonged to genotype Cosmopolitan. Conclusions The outbreak was caused by DENV-1 from Singapore and DENV-2 from Guangdong province in China. It is necessary to strengthen the surveillance and early warning for imported dengue fever, conduct vector control and improve the diagnosis of suspected dengue fever cases for the effective control of dengue fever outbreak.