Objective To investigate the genetic characteristics of the VP1 region of Coxsackievirus A10 (CVA10) in Yunnan Province. Methods Fecal samples of suspected hand, foot and mouth disease (HFMD) were subjected to real-time fluorescent quantitative PCR for detection of enterovirus CVA10. Positive samples were subjected to VP1 gene sequence amplification and Sanger sequencing. Sequence splicing was performed with DNAstar7.1 Seqman software, and nucleotide sequence and amino acid site analysis were performed using Mega 6.0 software. Results The sequencing of VP1 gene of CVA10 obtained a sequence of 894 nucleotides, encoding 298 amino acids. Compared with the original strain, there were mainly three active amino acid mutation regions, 13-33, 141-142, and 283-285. The nucleotide difference rate between the Yunnan isolates and the reference strain ranged from 16.92% to 30.90%, and the amino acid difference rate ranged from 2.58% to 4.00%. C1 and C2 group nucleotide difference was 10.58%, and the amino acid difference rate was 1.80%. The VP1 150-176 region exhibited highly conserved characteristics. Six CVA10 strains and Sichuan strain MW178898 belonged to the C1 group of the C genotype. The other 14 CVA10 strains belonged to the C2 group. Conclusion VP1 gene mutation is active and CVA10 is an important pathogen of HFMD in Yunnan. C2 genotype of CVA10 is dominant in this study, and C1 and C2 have co-circulated in Yunnan. It is necessary to strengthen monitoring and develop multivalent vaccines containing CVA10 epidemic genotype.

Objective:To investigate the predominant types of enteroviruses and the characteristics of the VP1 gene of coxsackievirus A4 (CVA4) causing hand, foot and mouth disease (HFMD) in Yunnan Province from 2018 to 2020.Methods:Throat swab and stool samples were collected from HFMD cases and tested by real-time quantitative PCR for nucleic acid detection. The samples positive for enterovirus nucleic acids were used for viral isolation and sent to the National Center for Disease Control and Prevention. The VP1 gene of the isolated strains was sequenced and analyzed.Results:From 2018 to 2020, a total of 21 757 HFMD samples were collected, 16 457 (75.64%) of which were positive for enteroviruses. Altogether 533 strains were isolated from 4 114 positive samples that were selected for viral isolation, including 89 strains of enterovirus 71 (EVA71, 16.70%), 180 strains of coxsackievirus A16 (CVA16, 33.77%), 76 strains of CVA10 (14.26%), 118 strains of CVA6 (22.14%), 26 strains of CVA4 (4.88%) and 44 strains of other types (8.26%). HFMD occurred mainly in children under five years old with higher incidence in males than in females (1.35∶1). The incidence of HFMD reached the peak in the second and third quarters. In Yunnan Province, CVA4 mainly circulated in Qujing and Kunming, and was sporadically detected in Wenshan and Honghe. The VP1 gene was 915 bp in length. Twenty-six CVA4 strains belonged to C2 subtype, which were genetically far from the prototype strain AY421762-HighPoint. Mutations in the VP1 gene were found at multiple sites including 18, 23, 34, 102, 148, 164, 200, 262, 174, 275, 285 and 303. These strains showed 80.4%-99.0% homology in nucleotide sequence and 95.6%-99.0% in amino acid sequence. Nucleotide mutations were mostly synonymous mutations.Conclusions:CVA16, CVA6, EVA71 and CVA10 were the predominant enteroviruses causing HFMD in Yunnan Province from 2018 to 2020. The prevalence of CVA4 was also worthy of attention. CVA4 isolates in Yunnan Province belonged to C2 subtype, mainly circulating in the east and southeast of Yunnan Province and gradually becoming a cocirculating predominant strain. Long-term dynamic monitoring would be of great public health significance for improving the sensitivity of HFMD early warning.