Coxsackievirus B3 (CV-B3) is usually associated with aseptic meningitis and myocarditis; however, the association between CV-B3 and hand, foot, and mouth disease (HFMD) has not been clearly demonstrated, and the phylogenetic dynamics and transmission history of CV-B3 have not been well summarized. Two HFMD outbreaks caused by CV-B3 were described in Hebei Province in 2012 and in Shandong Province in 2016 in China. To analyze the epidemiological features of two CV-B3 outbreaks, a retrospective analysis was conducted. All clinical specimens from CV-B3 outbreaks were collected and disposed according to the standard procedures supported by the WHO Global Poliovirus Specialized Laboratory. EV genotyping and phylogenetic analysis were performed to illustrate the genetic characteristics of CV-B3 in China and worldwide. Two transmissible lineages (lineage 2 and 3) were observed in Northern China, which acted as an important “reservoir” for the transmission of CV-B3. Sporadic exporting and importing of cases were observed in almost all regions. In addition, the global sequences of CV-B3 showed a tendency of geographic-specific clustering, indicating that geographic-driven adaptation plays a major role in the diversification and evolution of CV-B3. Overall, our study indicated that CV-B3 is a causative agent of HFMD outbreak and revealed the phylogenetic dynamics of CV-B3 worldwide, as well as provided an insight on CV-B3 outbreaks for effective intervention and countermeasures.

Background: Hand, foot, and mouth disease (HFMD) is an acute infectious disease caused by human enteroviruses (EVs). EVs are most prevalent in children under five years of age and have the potential to result in herpangina, HFMD, and severe complications, including encephalitis and death. Since the first outbreak was reported in 2008 in Finland, coxsackievirus A6 (CVA6) has spread rapidly and frequently undergone recombination events worldwide, posing a threat to the health of pediatric population around the globe.Aim of review: The dearth of vaccines and anti-CVA6 drugs hinders the efficient prevention and control of CVA6. However, over the course of the last decade, researchers have endeavored to develop potential vaccine candidates for CVA6 using various pathways. In this study, we present a systematic review of research progress pertaining to the CVA6 vaccines, with a particular emphasis on the most recent advancements in CVA6 vaccine development and evaluation. The objective of this review is to establish a theoretical foundation for the formulation of preventive and control strategies, as well as the development of vaccines against not only CVA6 but also other key serotypes in the future.Key scientific concepts of review: The review comprehensively addresses the diverse array of CVA6 vaccine development, encompassing a range of modalities such as inactivated, virus-like particle, and subunit vaccines, among others. A systematic analysis was conducted on animal-based assessments of various CVA6 vaccines, encompassing immunogenicity, protection rate, and cross-immunization as critical evaluation parameters. In light of the recurrent recombination of CVA6 and the evolution of pathogen profiles, the recommendation is made for the future development of multivalent and mRNA vaccines, which hold significant potential in the prevention and control of CVA6 and other major dominant serotypes.

Nineteen CVA9 isolates were obtained between 2010 and 2019 from six provinces of mainland China, using the HFMD surveillance network established in China. Nucleotide sequencing revealed that the full-length VP1 of 19 CVA9 isolates was 906 bases encoding 302 amino acids. The combination of the thresholds of the phylogenetic tree and nucleotide divergence of different genotypes within the same serotype led to a value of 15–25%, and enabled CVA9 worldwide to be categorized into ten genotypes: A–J. The phylogenetic tree showed that the prototype strain was included in genotype A, and that the B, C, D, E, H, and J genotypes disappeared during virus evolution, whereas the F, I, and G genotypes showed co-circulation. Lineage G was the dominant genotype of CVA9 and included most of the strains from nine countries in Asia, North America, Oceania, and Europe. Most Chinese strains belonged to the G genotype, suggesting that the molecular epidemiology of China is consistent with that observed worldwide. The 165 partial VP1 strains (723 nt) showed a mean substitution rate of 3.27 × 10⁻³ substitution/site/year (95% HPD range 2.93–3.6 × 10⁻³), dating the tMRCA of CVA9 back to approximately 1922 (1911–1932). The spatiotemporal dynamics of CVA9 showed the spread of CVA9 obviously increased in recent years. Most CVA9 isolates originated in USA, but the epidemic areas of CVA9 are now concentrated in the Asia–Pacific region, European countries, and North America. Recombination analysis within the enterovirus B specie (59 serotypes) revealed eight recombination patterns in China at present, CVB4, CVB5, E30, CVB2, E11, HEV106, HEV85, and HEV75. E14, and E6 may act as recombinant donors in multiple regions. Comparison of temperature sensitivity revealed that temperature-insensitive strains have more amino acid substitutions in the RGD motif of the VP1 region, and the sites T283S, V284M, and R288K in the VP1 region may be related to the temperature tolerance of CVA9.

The aim of this study was to determine the global genetic diversity and transmission dynamics of coxsackievirus B4 (CVB4) and to propose future directions for disease surveillance. Next-generation sequencing was performed to obtain the complete genome sequence of CVB4, and the genetic diversity and transmission dynamics of CVB4 worldwide were analyzed using bioinformatics methods such as phylogenetic analysis, evolutionary dynamics, and phylogeographic analysis. Forty complete genomes of CVB4 were identified from asymptomatic infected individuals and hand, foot, and mouth disease (HFMD) patients. Frequent recombination between CVB4 and EV-B multiple serotypes in the 3D^pol region was found and formed 12 recombinant patterns (A-L). Among these, the CVB4 isolated from asymptomatic infected persons and HFMD patients belonged to lineages H and I, respectively. Transmission dynamics analysis based on the VP1 region revealed that CVB4 epidemics in countries outside China were dominated by the D genotype, whereas the E genotype was dominant in China, and both genotypes evolved at a rate of > 6.50 × 10⁻³ substitutions/site/year. CVB4 spreads through the population unseen, with the risk of disease outbreaks persisting as susceptible individuals accumulate. Our findings add to publicly available CVB4 genomic sequence data and deepen our understanding of CVB4 molecular epidemiology.

Hand, foot, and mouth disease (HFMD), a common childhood infection caused by enterovirus, poses a serious public health concern in China. We collected and analyzed epidemiological data on 62,133 HFMD cases in Shenyang City, Liaoning Province, from 2013 to 2023. The average annual incidence was 76.12 per 100,000 person-years; 99.45% of cases were mild, while 0.55% were severe. Only one patient died. HFMD infections peaked annually in July. Children in kindergartens and scattered children accounted for 44.6% and 42.2% of cases, respectively. Real-time RT-PCR detection of enteroviruses in 5534 patient samples revealed 3780 positives, of which 25.1% were CVA16-positive. Positives were randomly sampled, yielding 240 VP1 sequences of CVA16. Phylogenetic tree results showed that all VP1 sequences belonged to the B1 sub-genogroup. However, the sub-genogroup prevalence varied over time: from 2013 to 2014 and 2019 to 2021, the predominant sub-genogroup was B1a, while it was B1b from 2015 to 2018. Further phylogenetic analyses showed substantial divergence between B1a branches in CVA16, suggesting possible turnover of the B1a sub-genogroup in CVA16 due to evolution. This study provides epidemiological data on HFMD in Shenyang, and provides a phylogenetic analysis of CVA16, offering a theoretical basis for preventing and controlling HFMD in Shenyang City.

Coxsackievirus B5 (CVB5) is an important enterovirus B species (EV-Bs) type. We used the full-length genomic sequences of 53 viral sequences from the national hand, foot, and mouth disease surveillance network in the Chinese mainland (2001–2021). Among them, 69 entire VP1 coding region nucleotide sequences were used for CVB5 genotyping and genetic evolution analysis. Phylogenetic analysis based on a data set of 448 complete VP1 sequences showed that CVB5 could be divided into four genotypes (A-D) worldwide. Sequences from this study belonged to genotypes B and D, which dominated transmission in the Chinese mainland. Two transmission lineages of CVB5 have been discovered in the Chinese mainland, lineage 2 was predominant. Markov chain Monte Carlo analysis indicated that the tMRCA of CVB5 in the Chinese mainland could be traced to 1955, while the global trend could be traced to 1862, 93 years earlier than China. The evolution rate of CVB5 was higher in the Chinese mainland than worldwide. The spatiotemporal dynamics analysis of CVB5 assessed that virus transportation events were relatively active in Central, Northeast, North and Northwest China. Recombination analysis revealed frequent intertypic recombination in the non-structural region of CVB5 genotypes B and D with the other EV-Bs, revealing eight recombination lineages. Our study showed the molecular evolution and phylogeography of CVB5 that could provide valuable information for disease prevention.