Objective　This study aimed to investigate the epidemiological characteristics, recombination patterns, and mutation variations of Coxsackievirus A6 (CV-A6) based on whole-genome sequences of CV-A6 collected from Anhui Province from 2022 to 2023, to understand the relationship between recombination and evolution in CV-A6. Methods　CV-A6-positive samples collected from different regions of Anhui Province during 2022-2023 were subjected to whole-genome sequencing. Genome sequence alignment, phylogenetic analysis, and similarity analysis were conducted using software tools such as MEGA11, SimPlot, and DNAstar. Amino acid mutation sites in the P1-P3 coding regions were also analyzed. Results　A total of 10 CV-A6 isolates were sequenced in this study. The nucleotide and amino acid sequence similarity among the 10 isolates ranged from 94.0% to 99.7% and 98.3% to 99.9%, respectively. Compared with the prototype strain, their nucleotide and amino acid sequence similarity ranged from 79.6% to 80.1% and 94.8% to 95.1%, respectively. The VP1 phylogenetic tree revealed that all 10 isolates belonged to the D3a subtype, consistent with the genotypic trends observed in recent years in China. Recombination analysis showed that the P1 coding region was relatively conserved, whereas certain levels of recombination events occurred between CV-A6 and other enteroviruses in the P2 and P3 coding regions. Recombination evolution analysis of the 3D region indicated that the CV-A6 strains were divided into two recombinant branches, RF-A and RF-K, with 4 isolates classified as RF-A and 6 as RF-K. Amino acid mutation site analysis showed varying degrees of mutations in the P1-P3 regions. Specifically, in the 3D region, RF-A and RF-K recombinant branches displayed different mutation patterns, with 13 unique amino acid mutations observed in the RF-A branch and 6 unique mutations in the RF-K branch. Conclusions　The D3a subtype is the predominant epidemic genotype of CV-A6 in Anhui Province during 2022-2023, and no evidence of emergent new sub-genotypes was observed. However, some mutations may have occurred in the 3D region, indicating potential genetic changes.

Objective:To understand the genome-wide sequence variation and molecular evolution of coxsackievirus A4 (CV-A4) strain in Anhui province, so as to provide a theoretical basis for the pathogenic monitoring and scientific prevention and treatment of hand, foot and mouth disease in the future.Methods:Five CVA4 isolates of 2020 were sequenced by first-generation sequencing method. MEGA11.0 was used to construct a phylogenetic tree based on VP1 region for 5 CV-A4 isolates, 32 CV-A4 strains and Enterovirus A71(EV-A71) prototype strain BrCr, and the isolates and enterovirus A (EV-A) prototype strains based on P1, P2 and P3 regions respectively, and DNAStar was used for amino acid sequence comparison in VP1 region. BioEdit7.2 was used for amino acid displacement entropy analysis and amino acid site entropy mapping. SimPlot3.5 and RDP4 were used for recombination analysis of CV-A4 isolate and EV-A prototype representative strains, and DnaSP6 software was used for selection pressure analysis of isolates and reference representative strains.Results:The phylogenetic tree showed that the isolates belonged to the C2 subtype, which belonged to the same clade as the CV-A4 strain circulating in Chinese mainland, and the amino acid sequence homology of the C2 subtype branch was 97.3%-100%, and the isolates had 6 amino acid variation sites compared with the prototype. The selection pressure analysis showed that the CV-A4 strain of the C2 subtype was affected by negative selection pressure, and there were 25 mutagenic sites in the amino acid sequence in the coding region of the displacement entropy analysis, accounting for 1.14%, and the evolution of the strain mainly depended on recombination. Recombination analysis showed that the isolates recombined with a variety of EV-A prototype strains in the P2 and P3 regions, and the recombination section with the CV-A5 prototype strain was longer, especially in the 3A-3C section, and P1 was a relatively conserved region.Conclusions:CV-A4 has frequent recombination events with other EV-A prototype strains in P2 and P3, and the molecular evolution of CV-A4 in Anhui should continue to be closely monitored.