Etiological surveillance of HFMD and the phylogenetic analysis of coxsackievirus A6 in Wenshan prefecture of Yunnan province, China, 2014 to 2018 / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To analyze the etiology of hand, foot and mouth disease (HFMD) cases collected from Wenshan prefecture from 2014 to 2018 and the molecular epidemiology of coxsackievirus A6(CV-A6).Methods:Viruses were isolated by RD cells and Hep-2 cells from stool samples collected from HFMD patients in Wenshan prefecture from 2014 to 2018. Virus RNA was extracted and virus VP4/VP2 junction region sequence was firstly amplified and sequenced by MD91 and OL68-1 primer pairs, then the virus serotype was determined. Virus entire VP1 gene sequences were determined by relative primer pairs according to the references. The reference sequences of CV-A6 virus entire VP1 gene were downloaded from the GenBank and the phylogenetic tree was constructed and the genetic characteristics and molecular epidemiology were analyzed.Results:During five years of study period, a total of 581 strains of enteroviruses (EVs) was isolated with an isolation rate of 20.40% (581/2 848). Among 581 strains, 74 strains were CV-A6, accounting for 12.74% (74/581); 124 were CV-A16, accounting for 21.34% (124/581); 374 were EV-A71, accounting for 64.37% (374/581); nine were other EVs, accounting for 1.55% (9/581). The entire VP1 sequences of 74 CV-A6 strains were filtered by constructing a phylogenetic tree and the completely same strains were excluded from analysis. We finally analyzed the phylogenetic characteristics of 22 strains isolated in this study with 52 reference strains. The results showed that all 22 Wenshan strains belonged to D3a sub-genotype, of which 21 strains belonged to cluster 1, and only one strain belonged to cluster 2.Conclusions:From 2014 to 2018, the outbreaks of HFMD in Wenshan prefecture were mainly caused by EV-A71, CV-A16 and CV-A6, accounting for 64.37%, 21.34% and 12.74% respectively. Phylogenetic analysis showed, similar to the situation in China, the sub-genotype D3a of CV-A6 was the predominant virus and the cluster 1 was the main sub-genotype in this outbreak.