2014-2018年昆明市重症手足口病病原柯萨奇病毒A6型的流行与遗传变异特点

Epidemiology and genetic characteristics of Coxsackievirus A6 isolated from patients with severe hand,foot,and mouth disease between 2014 and 2018 in Kunming

目的了解2014-2018年昆明市重症手足口病患者感染的柯萨奇病毒A6(Coxsackievirus A6,CV-A6)型流行情况及其全长VP1区基因特征。方法收集2014-2018年昆明市重症手足口病病例资料及标本1064份,采用Real Time RT-PCR方法进行肠道病毒核酸检测,分析其流行特征。利用随机数表随机选取63例重症CV-A6阳性标本,对其进行完整VP1区基因序列测定,使用Mega6.0软件进行序列分析并构建系统进化树,并比较其核苷酸、氨基酸同源性及氨基酸变异情况。结果2014-2018年昆明市重症手足口病例中共检出肠道病毒阳性标本666份,其中CV-A6阳性195份。5年中重症手足口病例报告数呈下降趋势,但每年均有重症CV-A6病例报告,发病高峰期在4~7月,呈单峰模式,6月达最高峰。感染病例中男女性别比为2.55∶1,≤2岁儿童居多(73.33%),且重点集中在官渡和西山两区。63个CV-A6毒株均位于D3基因亚型D3a进化分支,与国内多地区CV-A6处于共循环状态。该分支分为3个进化小分支,D3a.1包含2014-2016年的所有毒株及少量2017年、2018年毒株;D3a.2包含绝大多数2017年及2018年毒株,D3a.3只有1株2014年昆明株。VP1区氨基酸在多个位点上与原型株存在特异突变,氨基酸变异已呈现年度间规律性。结论CV-A6是引起昆明市重症手足口病主要抗原之一,持续开展CV-A6分子流行病学检测,对昆明市手足口病的防控具有重要意义。

Objective To analyze the epidemiology and the characteristics the VP1 gene of Coxsackievirus A6(CV-A6) isolated from patients with severe hand, foot, and mouth disease(HFMD) between 2014 and 2018 in Kunming, China. Methods Data and specimens were collected from 1 064 patients who were diagnosed with severe HFMD in Kunming from 2014 to 2018. Enterovirus RNA was amplified using real time RT-PCR and analyzed using descriptive epidemiology. Sixty-three CV-A6-positive patients with severe HFMD were randomly selected via a random number table, and the whole VP1-coding region was sequenced. The homology of the VP1 gene was determined using MEGA 6.0 and a phylogenetic evolution tree was constructed. Results Six hundred and sixty-six specimens from patients with severe HFMD were positive for an Enterovirus, and 195 were positive for CV-A6. Severe HFMD due to CV-A6 was reported in Kunming each year from 2014 to 2018, though cases tended to decrease. The peak period of incidence was from April to July, and incidence peaked in June. The ratio of male to female patients was 2.55:1. Most patients(73.33%) were younger than 2 years of age. Cases were concentrated in the Guandu and Xishan districts. All 63 CV-A6 strains were the D3 subgenotype, cluster D3 a, with 3 lineages co-circulating in many areas in China. The D3 a.1 lineage contains all of the strains from 2014 to 2016 and a small number of the strains from 2017 and 2018. The D3 a.2 lineage circulated from 2017-2018, while the D3 a.3 lineage contained one Kunming strain. There were specific mutations in amino acids in theVP1 region compared to the original strain, and regular annual variation was evident. Conclusion CV-A6 has become one of the main pathogens causing severe HFMD in Kunming. Continuing to test for CV-A6 is crucial to HFMD prevention and control in Kunming.