Epidemiological and genetic characteristics of EV71 strains circulating in Jiangsu Province from 2009 to 2018

Objective To analyze the molecular epidemiology, genetic variations and evolution of enterovirus 71 (EV71) strains isolated in Jiangsu Province from 2009 to 2018. Methods Statistical methods were used to analyze the data about epidemiological characteristics and results of pathogen detection in cases with EV71 infection in Jiangsu Province from 2009 to 2018. The complete VP1 sequences of 80 EV71 strains were amplified and sequenced for analysis of diversity and phylogenesis. Results A total of 41 858 enterovirus-positive hand, foot and mouth disease cases were reported in Jiangsu Province from 2009 to 2018. EV71 was the predominant pathogen, accounting for 36.52%, and responsible for most of the severe cases. However, the percentage of EV71 among all pathogens gradually decreased over time. EV71 infection reached the peak in April to June and mainly occurred in children aged six months to five years old with higher incidence in males than in females. In terms of regional distribution, EV71 infections were characterized by area clustering in Jiangsu Province, mainly detected in Nanjing, Suzhou, Wuxi and Lianyungang. The 80 EV71 isolates belonged to C4a genotype. Nucleotide differences between them and three vaccine strains (H07, FY23 and FY7VP5)were 0.6%-5.5%, 0.8%-5.7% and 1.9%-6.9% and amino acid difference were 0-1.4%, 0.3%-2.0% and 0.3%-2.0%, respectively. Amino acid mutations in the epitopes of the 80 EV71 strains did not marked by years or regions. Conclusions EV71 strains showed obvious epidemiological characteristics in time, population and regional distribution in Jiangsu Province from 2009 to 2018.All of the 80 EV71 isolates belonged to C4a subgenotype. The nucleotide sequences between them and the vaccine strains varied greatly, but the homology of amino acids was relatively high, indicating the existence of some synonymous mutations and no risk of antigenic drift. This study would provide reference for EV71 vaccination in Jiangsu Province. Key words: Hand, foot and mouth disease; Enterovirus 71; Epidemiology; Genetic characteristics