Full-genome analysis of emerging Coxsackievirus B4 genotype D strains associated with herpangina in eastern China

In 2024 herpangina surveillance in Yuhuan City, China, two Coxsackievirus B4 strains (Z168, Z296) were identified. Full-length genome sequencing revealed that both strains belonged to genotype D that was first documented in eastern China. The two strains showed the highest nucleotide similarity to Coxsackievirus B4 strains isolated in the UK (2017). In the recombination events, both major parental strains were identified as Coxsackievirus B4 strains isolated in France (2015 and 2017). Echovirus 11 and Coxsackievirus B5 were detected as minor parental strains, indicating intertypic recombination. Phylogenetically, Z168 and Z296 clustered closely with European genotype D strains (2013-2024) but were distant from previously reported Chinese genotype D strains (Yunnan 2013-2016; Tianjin 2019). Bayesian phylogeographic reconstruction suggested a complex global transmission history of Coxsackievirus B4 with increasing cross-border transmission in recent decades, including genotypes A, D and E transmitting among North America, Europe and Asia. Both strains possessed a unique amino acid substitution within a putative neutralizing epitope, suggesting potential antigenic evolution. These findings indicate that the Z168 and Z296 strains likely represent a recent European introduction, forming a lineage distinct from earlier Chinese genotype D isolates. This highlights the need for molecular surveillance to track Coxsackievirus B4 emergence and evolution.