Coxsackievirus A16 Research Articles

Epidemiology of Hand, Foot, and Mouth Disease and Genetic Characterization of Coxsackievirus A16 in Shenyang, Liaoning Province, China, 2013–2023

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.

An Outbreak of Acute Hemorrhagic Conjunctivitis Caused by Coxsackievirus A24 in Eastern Uttar Pradesh, India 2023

Introduction: Acute hemorrhagic conjunctivitis (AHC) outbreaks are caused mostly by viruses. During July-August 2023, there was a sudden spike in acute hemorrhage conjunctivitis cases in Eastern Uttar Pradesh, India. To identify the etiological and gain molecular epidemiology of the agent, the study was conducted. Methodology: Conjunctival swabs were collected from patients (n = 128) with presumed acute hemorrhage conjunctivitis visiting two tertiary care hospitals. Results: Enteroviruses infection was identified in 96 (75%) patients. In these patients, coxsackievirus A24 (CV-A24) infection was further confirmed by targeting the genetic regions of 3C protease and VP1. Furthermore, the study established the outbreak was caused by the genotype IV of CV-A24 with the highest genetic similarity with CV-A24 reported from Northeast India, China, and Pakistan circulating during the same period. The comparison of our study sequences with earlier Indian outbreak strains (2007) revealed four amino acid substitutions at the 3C region (“S21N,” “V30I,” “S66I,” and “V75I”) and three non-synonymous mutations at the VP1 region (“L16I,” “P21S,” and “N301D”). Conclusion: The study findings revealed that the AHC outbreak was caused by genotype IV of CV-A24 in this region. Molecular identification accompanied by phylogenetic analysis will be useful in studying the enterovirus epidemiology associated with AHC outbreaks.

Onychomadesis and Beau’s Lines- Rare Complications of Handfoot- and-mouth Disease

Hand-foot-and-mouth disease (HFMD) is a common self-limiting viral infection in children caused by Coxsackievirus A16 and human enterovirus 71, presenting with fever, erythematous papulovesicular eruptions/ blisters on the palms, soles, knees, buttocks, and oral mucosa. Although rare, complications may arise in nails e. g. onychomadesis (nail separation) and Beau’s lines (transverse lines on the nails). These typically appear within four to eight weeks of HFMD and persist for around 5-6 weeks. No active treatment is required and these nail changes resolve spontaneously within few weeks as the nail bed remain intact. We present here a boy of 4 years who presented with such nail changes after around 5 weeks of HFM disease and diagnosed as onychomadesis and Beau’s lines after ruling out other possible causes of nail changes. BANGLADESH J CHILD HEALTH 2023; VOL 47 (1) : 47-50

Broadly therapeutic antibody provides cross-serotype protection against enteroviruses via Fc effector functions and by mimicking SCARB2.

Enteroviruses contain multiple serotypes and can cause severe neurological complications. The intricate life cycle of enteroviruses involving dynamic virus-receptor interaction hampers the development of broad therapeutics and vaccines. Here, using function-based screening, we identify a broadly therapeutic antibody h1A6.2 that potently protects mice in lethal models of infection with both enterovirus A71 and coxsackievirus A16 through multiple mechanisms, including inhibition of the virion-SCARB2 interactions and monocyte/macrophage-dependent Fc effector functions. h1A6.2 mitigates inflammation and improves intramuscular mechanics, which are associated with diminished innate immune signalling and preserved tissue repair. Moreover, cryogenic electron microscopy structures delineate an adaptive binding of h1A6.2 to the flexible and dynamic nature of the VP2 EF loop with a binding angle mimicking the SCARB2 receptor. The coordinated binding mode results in efficient binding of h1A6.2 to all viral particle types and facilitates broad neutralization of enterovirus, therefore informing a promising target for the structure-guided design of pan-enterovirus vaccine.

A Red Alert for Eye Conjunctivitis in Pakistan: A Call for Action and Awareness

For the recent upsurge in the cases of conjunctivitis particularly in Punjab, Pakistan has reached an alarming level. Till September 2023, almost 395,929 cases have been reported only in Punjab because of such an endemic condition schools have been temporarily closed. About 17000 cases were reported alone in Bahawalpur nearly doubling the figures from the previous month but currently, the epicenter of the break is Lahore as the recent outbreaks have also been seen worldwide like Malaysia, Taiwan, Japan, Brazil, and India. The primary cause of the epidemic is coxsackievirusA24 confirmed through genomic analysis. Coxsackievirus A24 is a non-enveloped, positive-stranded RNA virus which produces a polyprotein that forms a structural and non-structural component. This is responsible for acute hemorrhage conjunctivitis which is a viral disease and can spread rapidly as the virus belongs to a highly contagious genotype 4. Its symptoms are redness, pain, irritation discharge from the eye, and light sensitivity with an incubation period of 24 to 48 hours. Transmission can occur through hand-to-eye and eye-to-hand contact of the infected person as well as through contaminated surfaces. As the virus has the belated to evolved rapidly preventive measures are a necessity which include prevention from touching the eyes, practicing regular hand washing, cleaning contact lenses frequently, avoiding the sharing of personal items and using protective eyewear.

The antiviral effect and potential mechanism of Houttuynia cordata thunb. (HC) against coxsackievirus A4

Ethnopharmacological relevanceHand, foot, and mouth disease (HFMD) is mainly caused by various of enteroviruses such as enterovirus 71 (EVA71), coxsackievirus A16 (CVA16), CVA6, and CVA10 in infants and children under 5 years old. During the past 5 years, CVA4 has become the dominant pathogen resulting in HFMD in China. However, there are no effective vaccines and antiviral drugs available. Houttuynia cordata Thunb (HC). is a Chinese herbal medicine eaten as vegetables for treating viral infection diseases, but whether HC has anti-CVA4 effect remains unclear. Aim of the studyIn this study, we want to investigate the antiviral activity of HC against CVA4 in vitro and in vivo and elucidate the potential mechanism of HC against CVA4. Materials and methodsMTT assay were used to evaluate the cytotoxicity of HC. Virus titers assay, CPE assay, violet staining and immunofluorescence were used to investigate the antiviral effect of HC against CVA4. A 13-day-old suckling mice model was established to evaluate the therapeutic efficacy of HC against CVA4 infection. Western blot, qRT-PCR and time-of-drug addition assay were performed to elucidate the potential mechanism of HC against CVA4 infection. ResultsMTT assay indicated the cytotoxicity concentration of HC on Vero cells and RD cells were more than 1 mg/ml, suggesting that the low cytotoxicity of HC. In vitro antiviral assay revealed that HC could dose-dependently prevent the CPE, suppress the release of newborn virus, and inhibit the replication of CVA4 by decreasing viral RNA transcription and protein expression with IC50 of 88.96 μg/mL. A time-of-addition assay showed that HC mainly exerted anti-CVA4 effect by inhibiting virus replication at the post-entry stage. In vivo results further demonstrated that HC could effectively prevent the lethal infection of CVA4 by promoting survival, improving clinical symptoms, prolonging the survival time, inhibiting excessive inflammatory responses, and reducing pathological injury in vivo. Mechanistic studies revealed inhibition of p38 MAPK and JNK pathway over-activation may be the primary mechanism of HC against CVA4 infection. ConclusionIn summary, our results for the first time demonstrated that HC not only effectively inhibited CVA4 replication, but also partially protected the lethal infection of CVA4 in vivo. Furthermore, pharmacological mechanism studies revealed that the primary mechanism of HC against CVA4 infection may be associated with its effect of inhibiting over-activation of p38 MAPK and JNK signaling pathways caused by enteroviruses. Our finding indicated that HC might be a potential innovative medicine for treating HFMD.

Spectrum of respiratory viruses identified from SARS-CoV-2-negative human respiratory tract specimens in Watansoppeng, Indonesia.

Respiratory infections account for millions of hospital admissions worldwide. The aetiology of respiratory infections can be attributed to a diverse range of pathogens including viruses, bacteria and fungi. SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2)-negative specimens from Wattansoppeng city, South Sulawesi, were analysed to study the spectrum of respiratory viruses. Samples were screened for influenza virus, enterovirus, Paramyxoviridae, Nipah virus, Coronaviridae and Pneumoviridae. Of 210 specimens, 19 were positive for respiratory syncytial virus (RSV)-A, RSV-B, human parainfluenza virus type 1 (HPIV-1), HPIV-2, human rhinovirus (HRV)-A, HRV-B, HRV-C, human metapneumovirus (HMPV), influenza A virus (IAV) and coxsackievirus A6 (CV-A6). Influenza virus was of seasonal H3N2 subtype. The HMPVs were of genotypes B1 and A2a, while one RSV-A was of the ON-1 genotype. The viruses mostly affected children with unknown severity.

Genotyping and phylogeographic dynamics of coxsackievirus A16

Coxsackievirus A16 (CV-A16) is one of the major pathogens of Hand, Foot and Mouth disease. Here, we analyzed 287 full-length genome sequences of CV-A16 found worldwide from 1994 to 2019 to see the genomic evolution characteristics. Full-length genome-based phylogenetic tree divided the viruses into five different genotypes, G-a to G-e. The CV-A16 strains circulating in China dominate G-a and G-c, but can also be found in other genotypes including G-b and G-e. Phylogeographic analysis showed a high diversity of CV-A16 distribution. In addition, recombination was shown to drive the genomic evolution of CV-A16 during past decades. However, the structural proteins still remain relative conserved while there is extensive genomic recombination. This study updates the phylogenetic and phylogeographic information of CV-A16 and provides insights into the genetic characteristics of CV-A16.

Enhanced production of recombinant coxsackievirus A16 using a serum-free HEK293A suspension culture system for bivalent enterovirus vaccine development

Coxsackievirus A16 (CVA16) is one of the primary pathogens that causes hand, foot, and mouth disease (HFMD) in young children. In previous studies, CVA16 vaccine development has encountered several challenges, such as inefficient replication of the CVA16 virus in present culture systems, the induction of only mild neutralizing antibody titers, and neutralizing antibodies induced by certain vaccine candidates that are unable to protect against CVA16 viral challenge. In this study, we constructed a DNA-launched CVA16 infectious clone (CVA16ic) based on the genomic sequence of the CVA16 N5079 strain to minimize interference from viral quasispecies. The biochemical properties of this CVA16ic strain were similar to those of its parental strain. Serum-free HEK293A suspension cells, which produced higher virus titers than Vero cells, were demonstrated to improve CVA16 production yields. In addition, our study showed that inactivated EV-A71 antigens could enhance the immunogenicity of inactivated CVA16 mature/full particles (F-particles), suggesting that a bivalent CVA16 and EV-A71 vaccine may be an effective strategy for CVA16 vaccine development. These findings are expected to provide novel strategies and accelerate the development of bivalent HFMD vaccines.

SAR Analysis of Novel Coxsackie virus A9 Capsid Binders.

Enterovirus infections are common in humans, yet there are no approved antiviral treatments. In this study we concentrated on inhibition of one of the Enterovirus B (EV-B), namely Coxsackievirus A9 (CVA9), using a combination of medicinal chemistry, virus inhibition assays, structure determination from cryogenic electron microscopy and molecular modeling, to determine the structure activity relationships for a promising class of novel N-phenylbenzylamines. Of the new 29 compounds synthesized, 10 had half maximal effective concentration (EC50) values between 0.64-10.46 μM, and of these, 7 had 50% cytotoxicity concentration (CC50) values higher than 200 μM. In addition, this new series of compounds showed promising physicochemical properties and act through capsid stabilization, preventing capsid expansion and subsequent release of the genome.

Genomic surveillance reveals low-level circulation of two subtypes of genogroup C coxsackievirus A10 in Nanchang, Jiangxi Province, China, 2015-2023.

In recent years, coxsackievirus (CV) A10 has been associated with increasing sporadic hand, foot, and mouth disease (HFMD) cases and outbreaks globally. In addition to mild symptoms such as pharyngitis and herpangina, CVA10-related complications or even fatality can occur. Currently, systematic phylogenetic studies of CVA10 are limited. In this study, we first explored the epidemiological and genetic characteristics of CVA10 in Nanchang, an inland southeastern city of China, based on the HFMD surveillance network from 2015-2023. Among 3429 enterovirus-positive cases, 110 (3.04%) were associated with CVA10, with a male-to-female ratio of 1.62. The median age of the CVA10 patients was 2.3 years (interquartile range, IQR 1.0-4.0), with 94.55% (104/110) of the patients aged less than 5 years. Phylogenetic analyses using the full-length VP1, 5'UTR, P1, P2, P3 sequences and near full-length genomes indicated that CVA10 strains (n = 57) isolated in Nanchang belonged to genogroup C; two strains identified in 2017 belonged to C1 subtypes clustered with strains from Vietnam, Madagascar, France and Spain; and the others belonged to C2 subtypes interdigitating with CVA10 isolates from mainland China, the United States and Australia. Through extensive analysis, we identified a rare F168Y mutation in epitope 4 of VP1 in a Madagascar strain of genogroup F and a Chinese strain of genogroup C. Based on Bayesian evolutionary analyses, the average nucleotide substitution rate for the VP1 gene of CV10 strains was 3.07×10-3 substitutions/site/year. The most recent common ancestor (tMRCA) of genogroup C was dated 1990.84, and the tMRCA of CVA10 strains from Nanchang was dated approximately 2003.16, similar to strains circulating in other regions of China, suggesting that the viruses were likely introduced and cryptically circulated in China before the establishment of the HFMD surveillance network. Recombination analysis indicated intertypic recombination of the Nanchang strain with the genogroup G strain in the 3D region. Given the shifting dominance of viral genotypes and frequent recombination events, the existing surveillance system needs to be regulated to enhance genomic surveillance efforts on a more diverse spectrum of genotypes in the future.

Monitoring the Influence of Hand, Foot, and Mouth Disease: New Guidelines on Patient Care during the 2011-2012 Multiwaves and Multivariant Outbreak in Hai Phong City, Vietnam.

From 2011 to 2012, Northern Vietnam suffered its first large-scale hand, foot, and mouth disease (HFMD) epidemic. Two sets of official guidelines were issued during the outbreak to handle the HFMD crisis. The city of Hai Phong was used as a model to analyze the impact of the released guidelines. A total of 9621 HFMD cases were reported in Hai Phong city from April 2011 to December 2012. Three distinct waves of HFMD occurred. Enterovirus A71 and Coxsackievirus A16 were successively associated with the epidemics. Two periods, before and after the guidelines' release, could be distinguished and characterized by different patient patterns. The time to admission and severity changed notably. Guideline publications help the health system refocus on the 0.5-3 years age group with the highest incidence of the disease. The three waves showed different special distribution, but the main routes of infection were rivers and local secondary roads, most likely through local trade and occupational movements of people.

Evolving pathogen trends and spatial–temporal dynamics of hand, foot, and mouth disease in Fengxian District, Shanghai (2009–2022)

Hand, foot, and mouth disease (HFMD) is a prevalent acute infectious disease caused by enteroviruses, presenting substantial public health challenges in Shanghai, especially among children. The dynamic nature of HFMD’s etiology necessitates an ongoing evaluation of its epidemiological and virological trends to inform effective control strategies. This study aims to investigate the epidemiological patterns and viral evolution of HFMD in Fengxian District, Shanghai, China, with a focus on shifts in predominant viral strains over a 14-year period. We conducted a retrospective analysis of HFMD cases reported to the National Notifiable Disease Reporting System in Fengxian District from January 1, 2009 to December 31, 2022. Epidemiological trends, strain prevalence, and demographic impacts were assessed. A total of 27,272 HFMD cases were documented during the study period, with incidence showing pronounced seasonal fluctuations—peaking in spring and summer and a lesser peak in autumn. The disease incidence demonstrated significant positive correlations with several meteorological variables: daily average temperature (r = 0.30, P < 0.05), relative humidity (r = 0.20, P < 0.05), wind speed (r = 0.17, P < 0.05), and precipitation (r = 0.17, P < 0.05). Geographically, Nanqiao Town, Fengcheng Town, and Xidu Subdistrict reported the highest incidence rates. The demographic analysis revealed a male-to-female ratio of 1.60:1, predominantly affecting children aged 1–3 years. Prior to 2017, Enterovirus 71 (EV71) and Coxsackievirus A16 (CoxA16) were the primary detected strains; post-2017, Coxsackievirus A6 (CoxA6) emerged as the dominant strain. Statistical analysis confirmed significant year-to-year variations in virus detection rates, with decreasing trends for EV71 and other enteroviruses and an increasing trend for CoxA6. The findings indicate a distinct seasonal incidence of HFMD in Fengxian District. This study underscores the need for targeted public health education, enhanced surveillance, and proactive measures in childcare facilities to mitigate disease spread during peak seasons. Moreover, the evolving viral landscape warrants accelerated efforts in vaccine development against new strains to reduce HFMD incidence.

Characterization of cross-reactivity of coxsackievirus A2 VP1-specific polyclonal antibodies with enterovirus A71, coxsackievirus A16, and coxsackievirus A6

Coxsackievirus A2 (CVA2) is associated with multiple diseases in children. Currently, there is limited research on immunological detection methods for CVA2. Herein, the VP1 gene of CVA2 strain 201711, belonging to cluster 2 within genotype D, was analyzed. The structures of VP1 from CVA2 strains 201711, 7-1 and 12-1, enterovirus A71 (EV-A71) strain 201713, coxsackievirus A16 (CVA16) strain 201717, and coxsackievirus A6 (CVA6) strain JLS10 were compared. The Escherichia coli BL21(DE3)/pET vector system was employed to express the recombinant protein containing the entire VP1 of CVA2 strain 201711. Mice were immunized with the purified protein, and the sera were collected and used to specifically identify the VP1 in CVA2-infected RD cells by Western blot and immunofluorescence assay. There was no evident cross-reactivity of the sera with the VP1 of EV-A71, CVA16, and CVA6 strains mentioned above. Therefore, this study provided mouse-specific anti-CVA2 VP1 polyclonal antibodies for CVA2 detection.

Detection of hotspots and coldspots of the incidence of hand, foot and mouth diseases: A case study in Ho Chi Minh city, Vietnam

Background: Hand, foot, and mouth disease (HFMD) is a common pediatric illness mostly caused by Coxsackievirus A16 (CV-A16) and Human Enterovirus 71 (EV-A71). HFMD has grown significantly over the last 20 years, and it has drawn a lot of attention. To better understand of the epidemiology of HFMD, this study aims to investigate the use of Getis-Ord’s 𝐺𝑖 ∗ statistic in the identification of hotspots and coldspots of HFMD in Ho Chi Minh city, Vietnam. Methods: Getis-Ord’s 𝐺𝑖 ∗ statistic was first applied to identify hotspots and coldspots of HFMD incidence including highhigh, low-low spatial clusters. HFMD cases and infection rates collected in Ho Chi Minh were then used to explore the spatial clusters of HFMD Finally, the main findings will be discussed and summarised. Results: It was found that the large number of hand, foot and mouth disease cases were mainly concentrated in the western area of Ho Chi Minh City. A total of 04 hotspot clusters and 05 coldspots of HFMD infection rate were detected in the 29th week of 2024 in the west, center and north of Ho Chi Minh City, respectively. Whereas, 06 hotspots and 04 coldspots of HFMD infection rate were detected in the 30th week of 2024 in the west, south and center of Ho Chi Minh City, respectively. Conclusions: The results of this investigation confirm the value of Getis-Ord's 𝐺𝑖 ∗ statistic in the detection of hotspots and coldspots associated with confirmed cases of HFMD.

The early communication stages between serine proteases and enterovirus capsids in the race for viral disintegration

Serine proteases are important environmental contributors of enterovirus biocontrol. However, the structural features of molecular interaction accounting for the susceptibility of enteroviruses to proteases remains unexplained. Here, we describe the molecular mechanisms involved in the recruitment of serine proteases to viral capsids. Among the virus types used, coxsackievirus A9 (CVA9), but not CVB5 and echovirus 11 (E11), was inactivated by Subtilisin A in a host-independent manner, while Bovine Pancreatic Trypsin (BPT) only reduced CVA9 infectivity in a host-dependent manner. Predictive interaction models of each protease with capsid protomers indicate the main targets as internal disordered protein (IDP) segments exposed either on the 5-fold vertex (DE loop VP1) or at the 5/2-fold intersection (C-terminal end VP1) of viral capsids. We further show that a functional binding protease/capsid depends on both the strength and the evolution over time of protease-VP1 complexes, and lastly on the local adaptation of proteases on surrounding viral regions. Finally, we predicted three residues on CVA9 capsid that trigger cleavage by Subtilisin A, one of which may act as a sensor residue contributing to enzyme recognition on the DE loop. Overall, this study describes an important biological mechanism involved in enteroviruses biocontrol.

Phylodynamic and Epistatic Analysis of Coxsackievirus A24 and Its Variant.

Coxsackievirus A24 (CV-A24) is a human enterovirus that causes acute flaccid paralysis. However, a Coxsackievirus A24 variant (CV-A24v) is the most common cause of eye infections. The causes of these variable pathogenicity and tissue tropism remain unclear. To elucidate the phylodynamics of CV-A24 and CV-A24v, we analyzed a dataset of 66 strains using Bayesian phylodynamic approach, along with detailed sequence variation and epistatic analyses. Six CV-A24 strains available in GenBank and 60 CV-A24v strains, including 11 Taiwanese strains, were included in this study. The results revealed striking differences between CV-A24 and CV-A24v exhibiting long terminal branches in the phylogenetic tree, respectively. CV-A24v presented distinct ladder-like clustering, indicating immune escape mechanisms. Notably, 10 genetic recombination events in the 3D regions were identified. Furthermore, 11 missense mutation signatures were detected to differentiate CV-A24 and CV-A24v; among these mutations, the F810Y substitution may significantly affect the secondary structure of the GH loop of VP1 and subsequently affect the epitopes of the capsid proteins. In conclusion, this study provides critical insights into the evolutionary dynamics and epidemiological characteristics of CV-A24 and CV-A24v, and highlights the differences in viral evolution and tissue tropism.

Changing Epidemiology of Hand, Foot, and Mouth Disease Causative Agents and Contributing Factors.

Hand, foot, and mouth disease (HFMD) is a common viral infection primarily affecting children. It causes vesicles on the skin and inside the mouth. Although most cases get better on their own, severe cases can lead to complications such as brain stem encephalitis, meningoencephalitis, acute flaccid paralysis, and pulmonary edema. Hand, foot, and mouth disease is caused by various enteroviruses, with enterovirus A71 (EV-A71) and coxsackievirus A16 being the most common. However, recent studies have shown a shift in the molecular epidemiology of HFMD-causing pathogens, with coxsackievirus A6 and coxsackievirus A10 causing more infections. In addition, extensive recombination events have been identified among enterovirus strains, which may have a role in faster evolution and extinction of dominant enterovirus serotypes. Other strains of enterovirus can also cause severe complications, and there has been an increase in mortality associated with brain stem encephalitis in children under 3 years of age and teenagers. Currently, there are no effective antiviral therapies available to treat enterovirus infections. Vaccines against EV-A71 have been approved and are now used in mainland China. Studying the changing epidemiology of HFMD pathogens and the evolution patterns of its causative agents is crucial in developing effective prevention and control strategies. Increased interest in the molecular epidemiology of HFMD causative agents has led to a better understanding of the critical drivers of HFMD outbreaks, which can inform efforts to prevent and control the disease.

Molecular Evolutionary Dynamics of Coxsackievirus A6 Causing Hand, Foot, and Mouth Disease From 2021 to 2023 in China: Genomic Epidemiology Study.

Hand, foot, and mouth disease (HFMD) is a global public health concern, notably within the Asia-Pacific region. Recently, the primary pathogen causing HFMD outbreaks across numerous countries, including China, is coxsackievirus (CV) A6, one of the most prevalent enteroviruses in the world. It is a new variant that has undergone genetic recombination and evolution, which might not only induce modifications in the clinical manifestations of HFMD but also heighten its pathogenicity because of nucleotide mutation accumulation. The study assessed the epidemiological characteristics of HFMD in China and characterized the molecular epidemiology of the major pathogen (CV-A6) causing HFMD. We attempted to establish the association between disease progression and viral genetic evolution through a molecular epidemiological study. Surveillance data from the Chinese Center for Disease Control and Prevention from 2021 to 2023 were used to analyze the epidemiological seasons and peaks of HFMD in Henan, China, and capture the results of HFMD pathogen typing. We analyzed the evolutionary characteristics of all full-length CV-A6 sequences in the NCBI database and the isolated sequences in Henan. To characterize the molecular evolution of CV-A6, time-scaled tree and historical population dynamics regarding CV-A6 sequences were estimated. Additionally, we analyzed the isolated strains for mutated or missing amino acid sites compared to the prototype CV-A6 strain. The 2021-2023 epidemic seasons for HFMD in Henan usually lasted from June to August, with peaks around June and July. The monthly case reporting rate during the peak period ranged from 20.7% (4854/23,440) to 35% (12,135/34,706) of the total annual number of cases. Analysis of the pathogen composition of 2850 laboratory-confirmed cases identified 8 enterovirus serotypes, among which CV-A6 accounted for the highest proportion (652/2850, 22.88%). CV-A6 emerged as the major pathogen for HFMD in 2022 (203/732, 27.73%) and 2023 (262/708, 37.01%). We analyzed all CV-A6 full-length sequences in the NCBI database and the evolutionary features of viruses isolated in Henan. In China, the D3 subtype gradually appeared from 2011, and by 2019, all CV-A6 virus strains belonged to the D3 subtype. The VP1 sequences analyzed in Henan showed that its subtypes were consistent with the national subtypes. Furthermore, we analyzed the molecular evolutionary features of CV-A6 using Bayesian phylogeny and found that the most recent common ancestor of CV-A6 D3 dates back to 2006 in China, earlier than the 2011 HFMD outbreak. Moreover, the strains isolated in 2023 had mutations at several amino acid sites compared to the original strain. The CV-A6 virus may have been introduced and circulating covertly within China prior to the large-scale HFMD outbreak. Our laboratory testing data confirmed the fluctuation and periodic patterns of CV-A6 prevalence. Our study provides valuable insights into understanding the evolutionary dynamics of CV-A6.

Molecular characteristics of the structure protein VP1 in Coxsackievirus A10 Isolates from China.

Coxsackievirus A10 (CVA10) is a non-enveloped, positive-sense single-stranded RNA virus classified within the Enterovirus genus in the Picornaviridae family. It is among the pathogens that can cause hand, foot and mouth disease. This study aimed to analyze the temporal and spatial distribution of CVA10 in China to understand its epidemiological characteristics of CVA10. We collected the VP1 sequences of CVA10 from January 1, 2004, to December 31, 2019, from the GenBank database and created the global map using MapChart. We selected 56 known CVA10 genotype sequences. Then, MEGA6.06 was used to construct a phylogenetic tree with the collected gene sequences and the known reference sequences for comparative analysis to assess the distribution of CVA10 genotypes in different countries between 2004 and 2019. CVA10 has been widely detected or reported globally. In China, the prevalent genotype of CVA10 was mainly genotype B before 2008 and genotype C after 2009. In other countries, the prevalence of genotype D was dominant, followed by genotypes C and F, and the prevalence of CVA10 varied from continent to continent. Monitoring CVA10 genotypes or evolutionary branches should be strengthened, and the study of epidemic genotype characteristics should be enhanced. This will serve as a basis for further research and development of monovalent CVA10 or polyvalent vaccines designed for effective disease prevention.