Molecular characterization of a novel clade echovirus 3 isolated from patients with hand-foot-and-mouth disease in southwest China.

Echovirus 3 (E3) belongs to the species Enterovirus B. Currently, three nearly whole-genome sequences of E3 are available in GenBank in China. In this study, we determined the whole genomic sequences of six E3 strains isolated from the stools of patients with hand-foot-and-mouth disease in Southwest China in 2022. Their nucleotide and amino acid sequences shared 82.1%-86.4% and 96.6%-97.2% identity with the prototype Morrisey strain, respectively, and showed 87.1% and 97.2% mutual identity. The six E3 strains are not clustered with other Chinese strains and formed a novel subgenotype (C6) with the recent American and British strains. Recombination analyses revealed that intertype recombination had occurred in the 2 C and 3D regions of the six E3 strains with coxsackieviruses B5 and B4, respectively. This study augments the nearly whole-genome sequences of E3 in the GenBank database and extends the molecular characterization of this virus in China.