ORIGINAL RESEARCH article
Front. Cell. Infect. Microbiol.
Sec. Clinical Infectious Diseases
This article is part of the Research TopicMolecular and Phylogenetic Insights for Diagnostics and Vaccine DevelopmentView all articles
Genetic Characterization of Human Enterovirus A71 genotypes C4 and B5 Circulating in Qingdao City, Shandong Province, China, from 2023 to 2024
Provisionally accepted
Jinling Gong1
Sitong Liu1
Song Liu1Rui Sun1Siying Xiao1Zhilei Su1Xin Jiang1Qiuge Zhang2Xiaoyan Shi1*Xianming Liu3*
Wang Zhaoguo1*- 1Qingdao Municipal Center for Disease Control and Prevention, Qingdao, China
- 2Qingdao University, Qingdao, China
- 3Qingdao Municipal Hospital Group, Qingdao, China
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EV-A71 is a major etiological agent of hand, foot, and mouth disease (HFMD), primarily affecting children under 5 years of age. EV-A71 comprises seven distinct genotypes, with the C4 genotype being endemic in China and the B5 genotype circulating widely in Southeast Asia. This study aimed to characterize EV-A71 from HFMD cases in Qingdao between 2023 and 2024. Among 2,083 samples, 27 were EV-A71-positive, and 19 isolates were successfully cultured. Whole-genome analysis revealed co-circulation of EV-A71 C4 genotype (5 strains) and B5genotype (14 strains). The C4 strains formed a distinct clade closely related to a strain isolated in China in 2019 and exhibited six lineage-specific mutations across structural (VP1, VP3) and non-structural (2A, 2B, 3B, 3D) protein regions. Regarding the EV-A71 B5 strains, they segregated into two lineages: Lineage I (12 strains) clustered with viruses from Vietnam's 2023 outbreak, comprising ten typical strains and two recombinants containing Coxsackievirus A4 (CV-A4)-derived sequences. Recombination occurred within 2C region in one strain and 2C-3C region in the other. The Lineage II strains contained two novel recombinants with Coxsackievirus A2 (CV-A2) sequences integrated into the 3A-3D region. Analysis of the VP1 region amino acid sequences revealed that the 17th residue remained S in all Qingdao strains, whereas nearly all strains from the 2023 hand-foot-mouth disease outbreak in Vietnam exhibited an S→G substitution at this position. Importance: This study provides the first confirmed evidence of EV-A71 B5 establishment in Qingdao since surveillance began in 2007. The concurrent transmission of multiple EV-A71 genotypes and lineages, exhibiting distinct evolutionary pathways and recombination events, highlights the critical need for continuous genomic surveillance to guide HFMD control and vaccine strategies in the region.
Keywords: hand foot and mouth disease, Enterovirus A71, phylogenetics, variation, recombination
Received: 12 Aug 2025; Accepted: 27 Nov 2025.
Copyright: © 2025 Gong, Liu, Liu, Sun, Xiao, Su, Jiang, Zhang, Shi, Liu and Zhaoguo. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Xiaoyan Shi
Xianming Liu
Wang Zhaoguo
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