Etiology of Multiple Non-EV71 and Non-CVA16 Enteroviruses Associated with Hand, Foot and Mouth Disease in Jinan, China, 2009-June 2013

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.

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

Introduction

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.

Methods

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.

Results

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.

Discussion

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.

Progress in research and development of preventive vaccines for children in China

The infant and child stage is an important stage for the continuation and development of human society. The initial years of life have a lasting impact on a child's future. Children under the age of 5 have an immature immune system, especially infants and young children under 6 months of age. At this stage, the population has a low immunity to pathogen infections, making them vulnerable to bacteria and viruses. Vaccination can enhance the immunity of infants and children to specific diseases, reduce the transmission rate of infectious diseases, and promote the development of global public health. This article summarizes the current application status of Rotavirus (RV) vaccine, Hand-foot -mouth disease (HFMD) vaccine, and Pneumococcal Conjugate Vaccine (PCV) in China, as well as the research progress of clinical trial vaccine, laying a foundation for subsequent vaccine development.

Global landscape of coxsackieviruses in human health

Coxsackieviruses-induced infections, particularly in infants and young children, are one of the most important public health issues in low- and middle-income countries, where the surveillance system varies substantially, and these manifestations have been disregarded. They are widespread throughout the world and are responsible for a broad spectrum of human diseases, from mildly symptomatic conditions to severe acute and chronic disorders. Coxsackieviruses (CV) have been found to have 27 identified genotypes, with overlaps in clinical phenotypes between genotypes. In this review, we present a concise overview of the most recent studies and findings of coxsackieviruses-associated disorders, along with epidemiological data that provides comprehensive details on the distribution, variability, and clinical manifestations of different CV types. We also highlight the significant roles that CV infections play in the emergence of neurodegenerative illnesses and their effects on neurocognition. The current role of CVs in oncolytic virotherapy is also mentioned. This review provides readers with a better understanding of coxsackieviruses-associated disorders and pointing the impact that CV infections can have on different organs with variable pathogenicity. A deeper knowledge of these infections could have implications in designing current surveillance and prevention strategies related to severe CVs-caused infections, as well as encourage studies to identify the emergence of more pathogenic types and the etiology of the most common and most severe disorders associated with coxsackievirus infection.

Genomic epidemiology of CVA10 in Guangdong, China, 2013-2021

Hand, Foot and Mouth Disease (HFMD) is a highly contagious viral illness primarily affecting children globally. A significant epidemiological transition has been noted in mainland China, characterized by a substantial increase in HFMD cases caused by non-Enterovirus A71 (EV-A71) and non-Coxsackievirus A16 (CVA16) enteroviruses (EVs). Our study conducts a retrospective examination of 36,461 EV-positive specimens collected from Guangdong, China, from 2013 to 2021. Epidemiological trends suggest that, following 2013, Coxsackievirus A6 (CVA6) and Coxsackievirus A10 (CVA10) have emerged as the primary etiological agents for HFMD. In stark contrast, the incidence of EV-A71 has sharply declined, nearing extinction after 2018. Notably, cases of CVA10 infection were considerably younger, with a median age of 1.8 years, compared to 2.3 years for those with EV-A71 infections, possibly indicating accumulated EV-A71-specific herd immunity among young children. Through extensive genomic sequencing and analysis, we identified the N136D mutation in the 2 A protein, contributing to a predominant subcluster within genogroup C of CVA10 circulating in Guangdong since 2017. Additionally, a high frequency of recombination events was observed in genogroup F of CVA10, suggesting that the prevalence of this lineage might be underrecognized. The dynamic landscape of EV genotypes, along with their potential to cause outbreaks, underscores the need to broaden surveillance efforts to include a more diverse spectrum of EV genotypes. Moreover, given the shifting dominance of EV genotypes, it may be prudent to re-evaluate and optimize existing vaccination strategies, which are currently focused primarily target EV-A71.

Structure-based virtual screening and fragment replacement to design novel inhibitors of Coxsackievirus A16 (CVA16)

Numerous studies have shown that hand, foot and mouth disease (HFMD) pathogen Coxsackievirus A16 (CVA16) can also cause severe neurological complications and even death. Currently, there is no effective drugs and vaccines for CVA16. Therefore, developing a drug against CVA16 has become critical. In this study, we conducted two strategies-virtual screening (VS) and fragment replacement to obtain better candidates than the known drug GPP3. Through VS, 37 candidate drugs were screened (exhibiting a lower binding energy than GPP3). After toxicity evaluations, we obtained five candidates, analysed their binding modes and found that four candidates could enter the binding pocket of the GPP3. In another strategy, we analysed the four positions in GPP3 structures by the FragRep webserver and obtained a large number of candidates after replacing different functional groups, we obtained eight candidates (that target the four positions above) with the combined binding score and synthetic accessibility evaluations. AMDock software was uniformly utilized to perform molecular docking evaluation of the candidates with binding activity superior to that of GPP3. Finally, the selected top three molecules (Lapatinib, B001 and C001) and its interaction with CAV16 were validated by molecular dynamics (MD) simulation. The results indicated that all three molecules retain inside the pocket of CAV16 receptor throughout the simulation process, and he binding energy calculated from the MD simulation trajectories also support the strong affinity of the top three molecules towards the CVA16. These results will provide new ideas and technical guidance for designing and applying CVA16 therapeutics.Communicated by Ramaswamy H. Sarma.

Screening of a new candidate coxsackievirus B1 vaccine strain based on its biological characteristics

Coxsackievirus B1 (CVB1) is one of the significant pathogens causing viral myocarditis, hand, foot, and mouth disease (HFMD), and aseptic meningitis, and it has been associated with type 1 diabetes (T1DM). No effective antiviral drugs against CVB1 infection or preventive vaccines are available. Due to the success of two inactivated vaccines against enterovirus 71 and poliovirus, an inactivated Vero cell-based CVB1 vaccine could be developed. In this study, we isolated a high-growth CVB1 virus strain KM7 in Vero cells and developed a Vero-adapted vaccine candidate strain KM7-X29 via three rounds of plaque purification and serial passages. The KM7-X29 strain was grouped into the GII sub-genotype, which belonged to the Chinese epidemic strain and grew to a titer of more than 10⁷ CCID50/ml in Vero cells. The inactivated CVB1 vaccine produced by the KM7-X29 strain induced an effective neutralizing antibody response in BALB/c mice, and maternal antibodies were able to provide a 100% protective effect against lethal challenges with a CVB1 strain in suckling BALB/c mice. Thus, the KM7-X29 strain might be used as a new candidate coxsackievirus B1 vaccine strain. The neonatal murine model of CVB1 infection will contribute to the development of the CVB1 vaccine.

Immune Efficacy of the EV71 Vaccine in Fujian Province, China: A Real-World Analysis of HFMD

EV71 vaccine immunization mainly protects the human population against severe and fatal HFMD and has a positive effect on reducing the overall incidence rates of HFMD and of hospitalized cases. In the analysis of data collected over 4 years, we compared HFMD's incidence rate, severity, and etiological changes in a target population before and after vaccine intervention. The incidence rate of HFMD decreased from 39.02‱ in 2014 to 11.02‱ in 2021, with a decrease rate of 71.7%, and the decrease was statistically significant (p < 0.001). The number of hospitalized cases decreased by 68.88%, the number of severe cases dropped by 95.60% and the number of deaths dropped to 0. The proportion of cases caused by the EV71 virus in different populations decreased significantly after the intervention, specifically, by 68.41% among individuals 0-4 years of age, by 74.32% among kindergarten children, by 86.07% in severe cases and by 100% with respect to the number of deaths.

Genetic characterization and molecular epidemiology of Coxsackievirus A12 from mainland China during 2010-2019

Coxsackievirus A12 (CVA12) is an enterovirus that has been isolated in many countries in recent years. However, studies on CVA12 are limited, and its effective population size, evolutionary dynamics and recombination patterns have not been clarified now. In this study, we described the phylogenetic characteristics of 16 CVA12 strains isolated from pediatric HFMD patients in mainland China from 2010 to 2019. Comparison of the nucleotide sequences and amino acid sequences with the CVA12 prototype strain revealed that the 16 CVA12 strains are identical in 78.8-79% and 94-94.2%, respectively. A phylodynamic analysis based on the 16 full-length VP1 sequences from this study and 21 sequences obtained from GenBank revealed a mean substitution rate of 6.61 × 10^-3 substitutions/site/year (95% HPD: 5.16-8.20 × 10^-3), dating the time to most recent common ancestor (tMRCA) of CVA12 back to 1946 (95% HPD: 1942-1947). The Bayesian skyline plot showed that the effective population size has experienced twice dynamic fluctuations since 2007. Phylogeographic analysis identified two significant migration pathways, indicating the existence of cross-provincial transmission of CVA12 in mainland China. Recombination analysis revealed two recombination patterns between 16 CVA12 strains and other EV-A, suggesting that there may be extensive genetic exchange between CVA12 and other enteroviruses. In summary, a total of 16 full-length CVA12 strains were reported in this study, providing valuable references for further studies of CVA12 worldwide.

Molecular characteristics of a coxsackievirus A12 strain in Zhejiang of China, 2019

Background

Enterovirus A (EV-A), such as enterovirus A71 (EV-A71), generally causes hand, foot, and mouth disease (HFMD). However, limited studies focused on uncommon enterovirus serotypes such as coxsackievirus A12 (CV-A12). This study aimed to provide evidence to determine the molecular characteristics of a CV-A12 strain isolated in Zhejiang province, China.

Methods

In routine surveillance of HFMD, we identified a child case with CV-A12 infection in 2019 in Zhejiang province, China. Enterovirus was examined by using real-time reverse transcription-PCR (qRT-PCR). A partial VP1 sequence was amplified to determine the serotype, and then a full-length CV-A12 genome was sequenced. Nucleotide and amino acid similarity was calculated with those CV-A12 strains available in GenBank. Recombination was detected using RDP 4 and SimPlot. Furthermore, phylogenetic analysis was conducted by using BEAST 1.10, and protein modeling was performed with I-TASSER webserver.

Results

A full-length CV-A12 genome PJ201984 was isolated in a Chinese child with HFMD. The similarities with complete coding sequences of the CV-A12 strains in GenBank ranged between 79.3–100% (nucleotide) and 94.4–100% (amino acid), whereas it was 88.7–100.0% (nucleotide) and 97.2–100% (amino acid) when excluding the CV-A12 prototype strain Texas-12. In PJ201984, amino acid variations were more divergent in P2 and P3 regions than those in P1; the majority of those variations in VP1 (13/15) and VP4 (7/8) were similar to those documented in recently isolated CV-A12 strains in China. Furthermore, recombination was identified in P2 region, which involved a CV-A5 strain collected in China. Phylogenetic analysis revealed that PJ201984 clustered together with multiple CV-A12 strains isolated in China and the Netherlands during 2013–2018, as compared to another cluster consisting of CV-A12 strains in China and France during 2009–2015. Additionally, protein models of VP1 and VP4 in PJ201984 were well predicted to be similar to VP1 protein of EV-A71 and VP4 protein of coxsackievirus A21, respectively.

Conclusions

The full-length CV-A12 genome was characterized to have common recombination in P2 region and be phylogenetically related to those CV-A12 strains isolated in recent years, suggesting a continual spread in China. It warrants strengthening the routine surveillance for uncommon enterovirus serotypes, particularly on possible recombination and variation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-022-01892-1.

Optimizing laboratory-based surveillance networks for monitoring multi-genotype or multi-serotype infections

With the aid of laboratory typing techniques, infectious disease surveillance networks have the opportunity to obtain powerful information on the emergence, circulation, and evolution of multiple genotypes, serotypes or other subtypes of pathogens, informing understanding of transmission dynamics and strategies for prevention and control. The volume of typing performed on clinical isolates is typically limited by its ability to inform clinical care, cost and logistical constraints, especially in comparison with the capacity to monitor clinical reports of disease occurrence, which remains the most widespread form of public health surveillance. Viewing clinical disease reports as arising from a latent mixture of pathogen subtypes, laboratory typing of a subset of clinical cases can provide inference on the proportion of clinical cases attributable to each subtype (i.e., the mixture components). Optimizing protocols for the selection of isolates for typing by weighting specific subpopulations, locations, time periods, or case characteristics (e.g., disease severity), may improve inference of the frequency and distribution of pathogen subtypes within and between populations. Here, we apply the Disease Surveillance Informatics Optimization and Simulation (DIOS) framework to simulate and optimize hand foot and mouth disease (HFMD) surveillance in a high-burden region of western China. We identify laboratory surveillance designs that significantly outperform the existing network: the optimal network reduced mean absolute error in estimated serotype-specific incidence rates by 14.1%; similarly, the optimal network for monitoring severe cases reduced mean absolute error in serotype-specific incidence rates by 13.3%. In both cases, the optimal network designs achieved improved inference without increasing subtyping effort. We demonstrate how the DIOS framework can be used to optimize surveillance networks by augmenting clinical diagnostic data with limited laboratory typing resources, while adapting to specific, local surveillance objectives and constraints.

Co-infection and enterovirus B: post EV-A71 mass vaccination scenario in China

BACKGROUND

Hand, foot, and mouth disease (HFMD) is a common child infectious disease caused by more than 20 enterovirus (EV) serotypes. In recent years, enterovirus A71 (EV-A71) has been replaced by Coxsackievirus A6 (CV-A6) to become the predominant serotype. Multiple EV serotypes co-circulate in HFMD epidemics, and this study aimed to investigate the etiological epidemic characteristics of an HFMD outbreak in Kunming, China in 2019.

METHODS

The clinical samples of 459 EV-associated HFMD patients in 2019 were used to amplify the VP1 gene region by the three sets of primers and identify serotypes using the molecular biology method. Phylogenetic analyses were performed based on the VP1 gene.

RESULTS

Three hundred and forty-eight cases out of 459 HFMD patients were confirmed as EV infection. Of these 191 (41.61%) were single EV infections and 34.20% had co-infections. The EVs were assigned to 18 EV serotypes, of which CV-A6 was predominant (11.33%), followed by CV-B1 (8.93%), CV-A4 (5.23%), CV-A9 (4.58%), CV-A 16 (3.49%) and CV-A10 and CVA5 both 1.96%. Co-infection of CV-A6 with other EVs was present in 15.25% of these cases, followed by co-infection with CV-A16 and other EVs. The VP1 sequences used in the phylogenetic analyses showed that the CV-A6, CV-B1 and CV-A4 sequences belonged to the sub-genogroup D3 and genogroups F and E, respectively.

CONCLUSION

Co-circulation and co-infection of multiple serotypes were the etiological characteristic of the HFMD epidemic in Kunming China in 2019 with CV-A-6, CV-B1 and CV-A4 as the predominant serotypes. This is the first report of CV-B1 as a predominant serotype in China and may provide valuable information for the diagnosis, prevention and control of HFMD.

National Surveillance of Acute Flaccid Paralysis Cases in Senegal during 2017 Uncovers the Circulation of Enterovirus Species A, B and C

Polioviruses have been eliminated in many countries; however, the number of acute flaccid paralysis cases has not decreased. Non-polio enteroviruses are passively monitored as part of the polio surveillance program. Previous studies have shown that some enteroviruses do not grow in conventional cell lines used for the isolation of poliovirus according to the WHO guidelines. In order to evaluate the presence of enteroviruses, real-time RT-PCR was performed on Human Rhabdomyosarcoma (RD)-positive and RD-negative stool samples. A total of 310 stool samples, collected from children under the age of 15 years with acute flaccid paralysis in Senegal in 2017, were screened using cell culture and real-time RT-PCR methods. The selected isolates were further characterized using Sanger sequencing and a phylogenetic tree was inferred based on VP1 sequences. Out of the 310 stool samples tested, 89 were positive in real-time RT-PCR. A total of 40 partial VP1 sequences were obtained and the classification analysis showed that 3 (13%), 19 (82.6%), and 1 (4.4%) sequences from 23 RD-positive non-polio enterovirus isolates and 3 (17.6%), 7 (41.1%), and 7 (41.1%) sequences from 17 RD-negative stool samples belonged to the species EV-A, B, and C, respectively. Interestingly, the EV-B sequences from RD-negative stool samples were grouped into three separate phylogenetic clusters. Our data exhibited also a high prevalence of the EV-C species in RD-negative stool samples. An active country-wide surveillance program of non-polio enteroviruses based on direct RT-PCR coupled with sequencing could be important not only for the rapid identification of the involved emergence or re-emergence enteroviruses, but also for the assessment of AFP’s severity associated with non-polio enteroviruses detected in Senegal.

Analysis of miRNAs Involved in Mouse Heart Injury Upon Coxsackievirus A2 Infection

Coxsackievirus A2 (CVA2) has recently been constantly detected, and is associated with viral myocarditis in children. Our previous study demonstrated that CVA2 led to heart damage in a neonatal murine model. However, the molecular mechanism of heart injury caused by CVA2 remains largely unknown. Emerging evidence suggests the significant functions of miRNAs in Coxsackievirus infection. To investigate potential miRNAs involved in heart injury caused by CVA2, our study, for the first time, conducted a RNA-seq in vivo employing infected mice hearts. In total, 87, 101 and 76 differentially expressed miRNAs were identified at 3 days post infection (dpi), 7 dpi and 7 dpi vs 3 dpi. Importantly, above 3 comparison strategies shared 34 differentially expressed miRNAs. These results were confirmed by quantitative PCR (qPCR). Next, we did GO, KEGG, and miRNA-mRNA integrated analysis of differential miRNAs. The dual-luciferase reporter assay confirmed the miRNA-mRNA pairs. To further confirm the above enriched pathways and processes, we did Western blotting and immunofluorescence staining. Our results suggest that inflammatory responses, T cell activation, apoptosis, autophagy, antiviral immunity, NK cell infiltration, and the disruption of tight junctions are involved in the pathogenesis of heart injury caused by CVA2. The dysregulated miRNAs and pathways recognized in the current study can improve the understanding of the intricate interactions between CVA2 and the heart injury, opening a novel avenue for the future study of CVA2 pathogenesis.

Genomic surveillance of coxsackievirus A10 reveals genetic features and recent appearance of genogroup D in Shanghai, China, 2016–2020

Coxsackievirus A10 (CVA10) is one of the major causative agents of hand, foot and mouth disease (HFMD). To investigate the epidemiological characteristics as well as genetic features of CVA10 currently circulating in Shanghai, China, we collected a total of 9,952 sporadic HFMD cases from January 2016 to December 2020. In the past five years, CVA10 was the fourth prevalent causatives associated with HFMD in Shanghai and the overall positive rate was 2.78%. The annual distribution experienced significant fluctuations over the past five years. In addition to entire VP1 sequencing, complete genome sequencing and recombination analysis of CVA10 isolates in Shanghai were further performed. A total of 64 near complete genomes and 11 entire VP1 sequences in this study combined with reference sequences publicly available were integrated into phylogenetic analysis. The CVA10 sequences in this study mainly belonged to genogroup C and presented 91%–100% nucleotide identity with other Chinese isolates based on VP1 region. For the first time, our study reported the appearance of CVA10 genogroup D in Chinese mainland, which had led to large-scale outbreaks in Europe previously. The recombination analysis showed the recombination break point located between 5,100 nt and 6,700 nt, which suggesting intertypic recombination with CVA16 genogroup D. To conclusion, CVA10 genogroup C was the predominant genogroup in Shanghai during 2016–2020. CVA10 recombinant genogroup D was firstly reported in circulating in Chinese mainland. Continuous surveillance is needed to better understand the evolution relationships and transmission pathways of CVA10 to help to guide disease control and prevention.

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Systematic profiles of genetic features of CVA10 near complete genome.

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First report of the appearance of CVA10 genogroup D in Chinese mainland.

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Genomic comparisons indicate the potential recombinant origin of CVA10 genogroup D.

Emergence of a novel recombinant of CV-A5 in HFMD epidemics in Xiangyang, China

Background

Hand, foot and mouth disease (HFMD) is caused by a variety of enterovirus serotypes and the etiological spectrum worldwide has changed since a large scale of outbreaks occurred in 1997.

Methods

A large number of clinical specimens of HFMD patients were collected in Xiangyang and genotyping was performed by qRT-PCR, conventional PCR amplification and sequencing. Among the 146 CV-A5 detected cases, the complete genome sequences of representative strains were determined for genotyping and for recombination analysis.

Results

It was found that CV-A5 was one of the six major serotypes that caused the epidemic from October 2016 to December 2017. Phylogenetic analyses based on the VP1 sequences showed that these CV-A5 belonged to the genotype D which dominantly circulated in China. Recombination occurred between the CV-A5 and CV-A2 strains with a breakpoint in the 2A region at the nucleotide 3791.

Conclusions

The result may explain the emergence of CV-A5 as one of the major pathogens of HFMD. A multivalent vaccine against HFMD is urgently needed to control the disease and to prevent emerging and spreading of new recombinants.

Epidemiological and molecular characteristics of circulating CVA16, CVA6 strains and genotype distribution in hand, foot and mouth disease cases in 2017 to 2018 from Western India

Hand, Foot, and Mouth disease (HFMD) is a mild exanthematous and febrile disease occurs in children aged ≤10 years old. The present study highlights clinical, epidemiological characteristics, distribution of enterovirus (EV) types, and sub genotypes in HFMD cases reported during 2017 to 2018 in Western India. A total of 93 clinical samples collected from 68 HFMD cases were included. The presence of EV-RNA was determined by 5'UTR based nested reverse transcription polymerase chain reaction followed by molecular typing, sub genotyping by VP1/2A junction or VP1, full VP1 gene amplification, and phylogenetic analysis. The study reports 80.64% (75/93) EV positivity and 94.66% (71/75) typing rate, with a predominant circulation of CVA16 and CVA6 strains. Sequence analysis revealed the presence of coxsackievirus (CV)A16 (57.7%), CVA6 (40.8%), and Echo1 (1.4%) strains. EV infections were predominantly observed in children aged 1 to 3 years old (43.9%). Although cases were reported throughout the year, peaked in July (15.8%) and August (24.6%) months and persisted till September (19.3%). All the CVA16 and CVA6 positive strains were genotyped using full VP1 gene amplification. All CVA16 Indian strains (n = 41) were clustered with rarely reported B1c sub genotype and CVA6 strains (n = 29) with E2 sub-lineage. The study highlights the genetic characteristics of circulating CVA16, CVA6, and Echo1 strains in HFMD cases from Western India. The emergence of CVA16 B1c genotype and sub-lineage E2 of CVA6 strains and their constant circulation further demands systemic surveillance studies on HFMD from different parts of India to facilitate the rapid diagnosis of CVA16 and CVA6 strains using the molecular and serological based approach and for intervention strategies.

Epidemical and etiological study on hand, foot and mouth disease following EV-A71 vaccination in Xiangyang, China

Coxsackievirus A6 (CV-A6) and Coxsackievirus A10 (CV-A10) have been emerging as the prevailing serotypes and overtaking Enterovirus A71 (EV-A71) and Coxsackievirus A16 (CV-A16) in most areas as main pathogens of hand, foot and mouth disease (HFMD) in China since 2013. To investigate whole etiological spectrum following EV-A71 vaccination of approximate 40,000 infants and young children in Xiangyang, enteroviruses were serotyped in 4415 HFMD cases from October 2016 to December 2017 using Real Time and conventional PCR and cell cultures. Of the typeable 3201 specimen, CV-A6 was the predominant serotype followed by CV-A16, CV-A10, CV-A5, CV-A2 and EV-A71 with proportions of 59.54%, 15.31%, 11.56%, 4.56%, 3.78% and 3.03%, respectively. Other 12 minor serotypes were also detected. The results demonstrated that six major serotypes of enteroviruses were co-circulating, including newly emerged CV-A2 and CV-A5. A dramatic decrease of EV-A71 cases was observed, whereas the total cases remained high. Multivalent vaccines against major serotypes are urgently needed for control of HFMD.

A neonatal murine model of coxsackievirus A4 infection for evaluation of vaccines and antiviral drugs

Coxsackievirus A4 (CVA4) infection can cause hand, foot and mouth disease (HFMD), an epidemic illness affecting neonatal and paediatric cohorts, which can develop to severe neurological disease with high mortality. In this study, we established the first ICR mouse model of CVA4 infection for the evaluation of inactivated vaccines and antiviral drug screening. The CVA4 YT226R strain was selected to infect the neonatal mice and three infectious factors were optimized to establish the infection model. The 3-day-old neonatal mice exhibited clinical symptoms such as hind limb paralysis and death. The severe inflammatory reactions were closely related to the abnormal expression of the acute phase response proinflammatory cytokine IL-6 and an imbalance in the IFN-γ/IL-4 ratio. Importantly, the inactivated CVA4 whole-virus vaccine induced humoral immune responses in adult females and the maternal antibodies afforded mice complete protection against lethal dose challenges of homologous or heterologous CVA4 strains. Both IFN-α2a and antiserum inhibited the replication of CVA4 and increased the survival rates of neonatal mice during the early stages of infection. This neonatal murine model of CVA4 infection will be useful for the development of prophylactic and therapeutic vaccines and for screening of antiviral drugs targeting CVA4 to decrease morbidity and mortality.

Genetic characterization of VP1 of coxsackieviruses A2, A4, and A10 associated with hand, foot, and mouth disease in Vietnam in 2012-2017: endemic circulation and emergence of new HFMD-causing lineages

While conducting sentinel surveillance of hand, foot, and mouth disease (HFMD) in Vietnam, we found a sudden increase in the prevalence of coxsackievirus A10 (CV-A10) in 2016 and CV-A2 and CV-A4 in 2017, the emergence of which has been reported recently to be associated with various clinical manifestations in other countries. However, there have been only a limited number of molecular studies on those serotypes, with none being conducted in Vietnam. Therefore, we sequenced the entire VP1 genes of CV-A10, CV-A4, and CV-A2 strains associated with HFMD in Vietnam between 2012 and 2017. Phylogenetic analysis revealed a trend of endemic circulation of Vietnamese CV-A10, CV-A4, and CV-A2 strains and the emergence of thus-far undescribed HFMD-causing lineages of CV-A4 and CV-A2. The Vietnamese CV-A10 strains belonged to a genotype comprising isolates from patients with HFMD from several other countries; however, most of the Vietnamese strains were grouped into a local lineage. Recently, emerging CV-A4 strains in Vietnam were grouped into a unique lineage within a genotype comprising strains isolated from patients with acute flaccid paralysis from various countries. New substitutions were detected in the putative BC and HI loops in the Vietnamese CV-A4 strains. Except for one strain, Vietnamese CV-A2 isolates were grouped into a unique lineage of a genotype that includes strains from various countries that are associated with other clinical manifestations. Enhanced surveillance is required to monitor their spread and to specify their roles as etiological agents of HFMD or "HFMD-like" diseases, especially for CV-A4 and CV-A2. Further studies including whole-genome sequencing should be conducted to fully understand the evolutionary changes occurring in these newly emerging strains.

National Epidemiology and Evolutionary History of Four Hand, Foot and Mouth Disease-Related Enteroviruses in China from 2008 to 2016

Hand, foot and mouth disease (HFMD) is a major public health concern in China. The most predominant enteroviruses that cause HFMD have traditionally been attributed to enterovirus A71 (EVA71) and coxsackievirus A16 (CVA16). Since its first large outbreak in 2008, the dominant HFMD pathogens are constantly changing. In 2013 and 2015, CVA6 exceeded both EVA71 and CVA16 to become the leading cause of HFMD in some provinces. However, there still lacks a comprehensive overview on the molecular epidemiology and evolution of HFMD-related enteroviruses at the national level. In this study, we performed systematic epidemiological analyses of HFMD-related enteroviruses using the data of 64 published papers that met the inclusion criteria, and conducted phylogenetic analyses based on 12,080 partial VP1 sequences identified in China before 31st June 2018. We found that EVA71 prevalence has decreased sharply but other enteroviruses have increased rapidly from 2008 to 2016 and that one subtype of each enterovirus is represented during the epidemic. In addition, four genotypes EVA71_C4, CVA16_B1, CVA6_D and CVA10_C are the most predominant enterovirus strains and collectively they cause over 90% of all HFMD cases in China according to the phylogenetic trees using representative partial VP1 sequences. These four major enterovirus genotypes have different geographical distributions, and they may co-circulate with other genotypes and serotypes. These results suggest that more molecular epidemiological studies should be performed on several enteroviruses simultaneously, and such information should have implications for virological surveillance, disease management, vaccine development and policy-making on the prevention and control of HFMD.

Construction and characterization of an infectious cDNA clone of coxsackievirus A 10

Background

Coxsackievirus A10 (CA10) constitutes one of the four major pathogens causing hand, foot and mouth disease in infants. Infectious clones are of great importance for studying viral gene functions and pathogenic mechanism. However, there is no report on the construction of CA10 infectious clones.

Methods

The whole genome of CA10 derived from a clinical isolate was amplified into two fragments and ligated into a linearized plasmid vector in one step by In-Fusion Cloning. The obtained CA10 cDNA clones and plasmids encoding T7 RNA polymerase were co-transfected into 293 T cells to rescue CA10 virus. The rescued virus was identified by SDS-PAGE, Western blotting and transmission electron microscopic. One-day-old ICR mice were intracerebrally inoculated with the CA10 virus and clinical symptoms were observed. Multiple tissues of moribund mice were harvested for analysis of pathogenic changes and viral distribution by using H&E staining, real-time PCR and immunohistochemical staining.

Results

CA10 viruses were rescued from the constructed cDNA clone and reached a maximum titer of 10^8.125TCID₅₀/mL after one generation in RD cells. The virus exhibited similar physical and chemical properties to those of the parental virus. It also showed high virulence and the ability to induce death of neonatal ICR mice. Severe necrotizing myositis, intestinal villus interstitial edema and severe alveolar shrinkage were observed in infected mice. The viral antigen and the maximum amount of viral RNA were detected in limb skeletal muscles, which suggested that the limb skeletal muscles were the most likely site of viral replication.

Conclusion

Infectious clones of CA10 were successfully constructed for the first time, which will facilitate the establishment of standardized neonatal mouse models infected with CA10 for the evaluation of vaccines and antiviral drugs, as well as preservation and sharing of model strains.

Hand, foot, and mouth disease associated with coxsackievirus A10: more serious than it seems

INTRODUCTION

Hand, foot, and mouth disease (HFMD) is a common viral childhood illness, that has been a severe public health concern worldwide, particularly in the Asia-Pacific region. According to epidemiological data of HFMD during the past decade, the most prevalent causal viruses were enterovirus (EV)-A71, coxsackievirus (CV)-A16, CV-A6, and CV-A10. The public health burden of CV-A10-related diseases has been underestimated as their incidence was lower than that of EV-A71 and CV-A16 in most HFMD outbreaks. However, cases of CV-A10 infection are more severe, and its genome is more variable, which has alerted the research community worldwide. Areas covered: In this paper, studies on the epidemiology, laboratory diagnosis, clinical manifestations, molecular epidemiology, seroepidemiology, animal models of CV-A10, and vaccines and antiviral strategies against this genotype are reviewed. In addition, the genetic evolution of circulating strains was analyzed. Expert opinion: Multivalent vaccines against EV-A71, CV-A16, CV-A6, and CV-A10 should be a next-step HFMD vaccine strategy.

Profiles of Human Enteroviruses Associated with Hand, Foot, and Mouth Disease in Nanjing, China

OBJECTIVE

Hand, foot, and mouth disease (HFMD) is a common infectious disease caused by a group of viruses. The causative viruses have changed over time, and there is a need for a more effective protective vaccine. In this study, we investigated the profiles of human enteroviruses that caused HFMD outbreaks in Nanjing in 2015, with the goal of guiding the future prevention and treatment of HFMD.

METHODS

Specimens were collected from 1097 patients admitted to our hospital and diagnosed with HFMD. Enteroviruses in the specimens were identified by real-time polymerase chain reaction and epidemiological patterns were analyzed with the clinical data.

RESULTS

Among the 1097 clinically diagnosed HFMD cases, 916 cases were confirmed by laboratory tests. The results showed that the main infectious virus was coxsackievirus A6 (CVA6) (41.75%), followed by enterovirus 71 (EV71) (27.48%), coxsackievirus A16 (7.43%), coxsackievirus A10 (6.84%), and others (16.51%). Further investigation indicated that CVA6 caused mild cases of HFMD, while EV71 caused severe cases. More enterovirus positive cases were reported from rural areas than from urban areas.

CONCLUSIONS

CA6 and EV71 were the chief pathogenic viruses of HFMD cases in the present study. Schools, childcare centers, and families from rural areas should be the major targets for prevention and awareness of HFMD. This study will provide information useful in the prevention and management of HFMD and the development of relevant vaccines for HFMD in the future. (Disaster Med Public Health Preparedness. 2019;13:740-744).

Surveillance for severe hand, foot, and mouth disease from 2009 to 2015 in Jiangsu province: epidemiology, etiology, and disease burden

Background

Severe hand, foot, and mouth disease (HFMD) is a common childhood illness caused by various enteroviruses. The disease has imposed increased burden on children younger than 5 years old. We aimed to determine the epidemiology, CNS complication, and etiology among severe HFMD patients, in Jiangsu, China.

Methods

Epidemiological, clinical, and laboratory data of severe HFMD cases were extracted from 2009 to 2015. The CNS complication, annually severe illness rates, mortality rates, severity-PICU admission rates, severity-hospitalization rates, and so on were analyzed to assess the disease burden of severe HFMD. All analyses were stratified by time, region, population, CNS involvement and serotypes. The VP1 gene from EV-A71, CV-A16, CV-A6, CV-A10 and other enteroviruses isolates was amplified. Phylogenetic analysis was performed using MEGA5.0.

Results

Seven thousand nine hundred ninety-four severe HFMD cases were reported, of them, 7224 cases were inpatients, 611 were PICU inpatients, and 68 were fatal. The average severe illness rate, mortality rate, severity−fatality rate, severity-PICU admission rate, and severity-hospitalization rate were 14.54, 0.12,8506, 76,430, and 903,700 per 1 million, respectively. The severe illness rate was the highest in the 12–23 months age group, and the greatest mortality rate was in the 6–11 months age group. Geographical difference in severe illness rate and mortality were found. Patients infected with EV-A71 were at a higher proportion in different CNS involvement even death. EV-A71, CV-A16 and other enteroviruses accounted for 79.14, 6.49, and 14.47%, respectively. A total of 14 non-EV-A71/ CV-A16 genotypes including CV-A2, CV-A4, CV-A 6, CV-A9, CV-A10, CV-B1, CV-B2, CV-B3, CV-B4, CV-B5, E-6, E-7, E-18, and EV-C96 were identified. Phylogentic analyses demonstrated that EV-A71 strains belonged to subgenotype C4a, while CV-A16 strains belonged to sub-genotype B1a and sub-genotype B1b of genotype B1. CV-A6 strains were assigned to genogroup F, and CV-A10 strains belonged to genogroup D.

Conclusions

Future mitigation policies should take into account the age, region heterogeneities, CNS conditions and serotype of disease. Additional a more rigorous study between the mild and severe HFMD should be warranted to elucidate the difference epidemiology, pathogen spectrum and immunity patterns and to optimize interventions in the following study.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3659-7) contains supplementary material, which is available to authorized users.

The emerging sub-genotype C2 of CoxsackievirusA10 Associated with Hand, Foot and Mouth Disease extensively circulating in mainland of China

Coxsackievirus A10 (CV-A10) associated with Hand, foot, and mouth disease (HFMD) cases emerged increasingly in recent years. In this study, the samples from nation-wide HFMD surveillance, including 27 out of 31 provinces in China were investigated, and the continuous and extensive virological surveillance, covered 13 years, were conducted to provide a comprehensive molecular characterization analysis of CV-A10. 855 CV-A10 viruses (33 severe cases included), were isolated from HFMD children patients during 2009 to 2016 in China. 164 representative sequences from these viruses, together with 117 CV-A10 sequences downloaded from GenBank based on entire VP1 were recruited in this study. Two new genotypes (F and G) and two sub-genotypes (C1 and C2) were identified. Among 264 Chinese sequences, 9 of them were genotype B, 8 of them were C1, and the other (247) were C2, the predominant sub-genotype in China since 2012. Chinese C2 viruses showed obvious temporal characteristics and can be divided into 3 clusters (cluster 1~3). Cluster 3 viruses was circulating extensively during 2014 and 2016 with more severe cases. It is very necessary and important to continuously conduct the extensive virological surveillance for CV-A10, and further evolutionary studies will provide more evidence on its evolution and virulence.

Molecular characteristics of hand, foot, and mouth disease for hospitalized pediatric patients in Yunnan, China

Hand, foot, and mouth disease (HFMD) is a common infectious disease caused by multiple enteroviruses (EVs) in China. To better define the etiologic agents and clinical characteristics of HFMD, we conducted this study in Yunnan, China.In this study, 1280 stool specimens were collected from pediatric patients hospitalized for treatment of HFMD in 2010. EV was detected with nested reverse transcription polymerase chain reaction and directly genotyped by gene sequencing of the viral protein 1 (VP1) region. Phylogenetic analysis was performed based on the VP1 partial gene and the clinical characteristics were analyzed using SPSS Software.Of 1280 specimens, 1115 (87.1%) tested positive for EV. Seventeen different EV serotypes were detected. Coxsackievirus A16 (CA16) was the most frequently detected serotype (615/1115 cases, 55.1%), followed by enterovirus 71 (EV71; 392/1115, 35.2%), CA10 (45/1115, 4.0%), and CA4 (23/1115, 2.1%). Among the 709 severe cases, CA16, EV71, CA10, and CA4 accounted for 48.0%, 42.0%, 3.5%, and 2.3%, respectively. Of the 26 critical cases, 13 were caused by EV71, 9 by CA16, 2 by CA4, and 1 each were the result of CA10 and E9, respectively. All EV71, CA16, CA10, and CA4 isolates were highly homologous to the strains isolated from mainland China, and belonged to the C4a, B1a, G, and C genotypes, respectively.Our study showed that EV71 and CA16 were the main causative agents for severe and critical HFMD, but other serotypes can also cause severe and critical cases.

Enterovirus B74 associated with hand, foot and mouth disease

Enterovirus 74 (EV-B74) has been associated with cases of acute flaccid paralysis (AFP) but it is not a commonly found enterovirus. In this work, we present the characterization of an EV-B74 detected from the serum sample of a one-year-old boy presenting with signs and symptoms clinically compatible with hand, foot and mouth disease (HFMD). This is the first report of EV-B74 in Brazil.

Comprehensive virome analysis reveals the complexity and diversity of the viral spectrum in pediatric patients diagnosed with severe and mild hand-foot-and-mouth disease

The management of hand-foot-and-mouth disease(HFMD) epidemic is difficult due to the frequent emergence of non-EV71 and non-CVA16 enteroviruses and some cases testing negative for HFMD-associated causative agents. To clarify the virus spectrum of mild and severe HFMD, a comprehensive virome analysis of 238 samples was performed using next-generation sequencing (NGS). The data revealed total thirteen mammalian- and plant- virus families and diverse viral populations including enteroviruses, common respiratory viruses, diarrhea-related viruses, plant viruses and anelloviruses. A total of 18 viruses from 7 virus families were identified in severe cases, versus 37 viruses from 12 virus families in mild cases. Moreover, complicated mixed-infections of enteroviruses with common respiratory viruses were mainly found in severe cases(P = 0.013), while diarrhea-related viruses were mainly found in mild cases(P < 0.001). This study provides the preliminary understanding of viromes both in mild and severe cases, which may benefit the detection of etiologic agents and prevention of HFMD.

Development of a reverse transcription recombinase-aided amplification assay for the detection of coxsackievirus A10 and coxsackievirus A6 RNA

Hand, foot and mouth disease (HFMD) is a serious public health problem, and coxsackievirus A6 (CVA6) and coxsackievirus A10 (CVA10) are two of the major causative pathogens, in addition to enterovirus 71 (EV71) and coxsackievirus A16 (CVA16). A simple and rapid reverse transcription recombinase-aided amplification assay (RT-RAA) was developed for the detection of CVA10 and CVA6 in this study. The analytical sensitivity for detection of CVA10 and CVA6 at 95% probability by probit regression analysis was 35 copies per reaction and 38 copies per reaction, respectively, with 100% specificity. Compared with commercial RT-qPCR assays, when testing 455 fecal specimens, the kappa value of the RT-RAA assay for CVA10 and CVA6 was 0.920 (p < 0.001) and 0.952 (p < 0.001), respectively. Moreover, four samples that were positive for CVA10 and five that were positive for CVA6 by RT-RAA but negative by RT-qPCR were further determined to be true positives. These results demonstrate that the proposed RT-RAA assays are very valuable tools for the detection of CVA10 and CVA6 and have potential for use in resource-limited settings.

Prevalence of enteroviruses in healthy populations and excretion of pathogens in patients with hand, foot, and mouth disease in a highly endemic area of southwest China

Etiological carriers and the excretion of the pathogens causing hand, foot, and mouth disease (HFMD) in healthy persons, patients, and asymptomatic persons infected with HFMD as ongoing infection sources may play an important role in perpetuating and spreading epidemics of HFMD. The aims of this study were to determine the carrier status of EV-A71 and CV-A16 in healthy populations, as well as the duration of EV-A71 and CV-A16 shedding in the stools of HFMD patients in an epidemic area of southwest China. A cross-sectional study and a follow-up study were conducted in three HFMD endemic counties of Yunnan Province. Six hundred sixty-seven healthy subjects were recruited to participate in the cross-sectional study, and two stool specimens were collected from each subject. Among the healthy subjects, 90 (13.5%) tested positive for viral isolation, but neither EV-A71 nor CV-A16 was detected in healthy individuals. Of the 150 patients with probable HFMD, 55.3% (83/150) tested positive for viral isolation with presented serotypes such as EV-A71 (51.81%, 43/83), CV-A16 (32.53%, 27/83), other EVs (13.25%, 11/83), and mixed EV-A71 and CV-A16 (2.41%, 2/83). The longest duration of EV-A71 and CV-A16 shedding in stool specimens from patients with HFMD was >46 days after onset. The positive rate of EV-A71 in the stool specimens of confirmed patients dropped to 50% by the end of the third week, and the same occurred with CV-A16 by the end of approximately the seventh week after onset. Although carriers of major causative agents of HFMD in healthy populations are fewer in number, the prolonged shedding of pathogens in patients with HFMD may serve as an important factor in perpetuating and spreading HFMD epidemics.

Identification and molecular characterization of non-polio enteroviruses from children with acute flaccid paralysis in West Africa, 2013-2014

Besides polioviruses, non-polio enteroviruses (NPEVs) may also be associated with acute flaccid paralysis (AFP). Because poliomyelitis is on the verge of eradication, more attention should be paid to study NPEVs from non-polio AFP cases and their epidemic patterns. In West African countries the epidemiology of NPEVs remains largely unexplored. We investigated the genetic diversity, frequency, circulation patterns, and molecular epidemiology of NPEVs in seven West African countries by analyzing retrospectively a panel of 3195 stool samples from children with AFP collected through routine poliomyelitis surveillance activities between 2013 and 2014. VP1 sequencing and typing on 201 isolates revealed 39 NPEV types corresponding to EV-A (6.9%), EV-B (90.5%), EV-C (2%) and EV-D (0.5%) species. Echoviruses were isolated most frequently with 138 cases (68.6%), followed by coxsackievirus group B with 35 cases (17.4%). No single NPEV type was remarkably dominant. Interestingly, several rarely described types with limited detection worldwide were identified (EVA76, EVA119, EVB75, EVB77, EVB97, EVC99, CVA20, CVA21 and EVD94). This study demonstrates the extensive diversity and diverse circulation patterns of NPEVs from AFP surveillance and highlights the need to formulate effective long-term strategies to monitor NPEV circulations in West Africa.

A neonatal mouse model of coxsackievirus A10 infection for anti-viral evaluation

Epidemiological data indicate that coxsackievirus A10 (CVA10) has become one of the main causative agents of hand, foot and mouth disease (HFMD) and in recent years has often been found to co-circulate with other enteroviruses, which poses a challenge for the prevention and control of HFMD. Although most CVA10-associated HFMD cases present mild symptoms, severe manifestations and even death can also occur. However, the study of the pathogenesis and the development of drugs and vaccines for CVA10 infection are still far from complete. In this study, we established a neonatal mouse model for anti-viral evaluation and characterized the pathology of CVA10 infection. To develop the mouse model, both inbred and outbred mouse strains were used to compare their sensitivity to CVA10 infection; then, one-day-old BALB/c mice were selected and inoculated intraperitoneally with a CVA10 clinical strain, CVA10-FJ-01. Clinical symptoms, such as wasting, hind-limb paralysis and even death were observed in the CVA10-infected mice. Moreover, pathological examination and immunohistochemistry staining showed that severe myonecrosis with inflammatory infiltration was observed in CVA10-infected mice, indicating that CVA10 exhibited strong tropism to muscle tissue. Using real-time PCR, we also found that the viral load in the blood and muscle was higher than that in other organs/tissues at different time points post-infection, suggesting that CVA10 had a strong tropism to mice muscle and that viremic spread may also contribute to the death of the CVA10-infected mice. Additionally, to evaluate the neonatal mouse model of CVA10 infection, female mice were immunized with formalin-inactivated CVA10 and then allowed to mate after the third immunization. The results showed that maternal antibodies could protect mice against CVA10 infection. In summary, the results demonstrated that the neonatal mice model was a useful tool for evaluating the protective effects of CVA10 vaccines and anti-viral reagents.

Serotyping and Genetic Characterization of Hand, Foot, and Mouth Disease (HFMD)-Associated Enteroviruses of No-EV71 and Non-CVA16 Circulating in Fujian, China, 2011-2015

BACKGROUND Hand, foot, and mouth disease (HFMD) is a common contagious disease in infants; it is caused by multiple serotypes of human enterovirus (EV), which belongs to the enterovirus genus of the picornavirus family. According to sentinel surveillance, infection with EVs other than EV71 and CVA 16 have become increasingly common in recent years among HFMD patients, posing new challenges for HFMD control. This study aimed to explore the spectrum of serotypes in the other EVs (non-EV71 and non-CVA16) in Fujian province in southeastern China. MATERIAL AND METHODS We investigated 562 samples from EVs-infected HFMD patients with diagnosis confirmed by real-time RT-PCR with other EVs infection between 2011 and 2015. Nucleotide acid detection and the serotyping of the enteroviruses were also performed. The complete VP1 gene was amplified and sequenced. VP1-based phylogenetic analyses of CVA6, CVA10, CVA4, and CVA2 were also performed. RESULTS Among the samples, 22 serotypes of the other EVs, which belong to 4 species of human enterovirus A-D, were identified. Of the 22 serotypes, CVA6 (57.8%) and CVA10 (21.0%) were most common, followed by CVA4 (6.8%) and CVA2 (2.7%). The other 18 serotypes accounted for 11.7% of samples, none of which exceeded 2%. Among 47 (8.4%) samples from patients with severe HFMD, 10 serotypes were identified and most samples belonged to CVA6 (20/47), followed by CVA10 (11/47). Entire VP1 comparison revealed that overall genetic identities were 96.7%, 96.3%, 94.4%, and 94.9% among strains within CVA6, CVA10, CVA4, and CVA2, respectively. CONCLUSIONS VP1-based phylogenetic analysis for the 4 predominant serotypes indicated various clades or sub-clades, which suggests the complex transmissions of other enteroviruses in Fujian.

Severe hand, foot and mouth disease associated with Coxsackievirus A10 infections in Xiamen, China in 2015

BACKGROUND

Coxsackievirus A10 (CV-A10) is one of the etiological agents associated with hand, foot and mouth disease (HFMD) and usually causes mild cases. During 2009-2014, no severe cases caused by CV-A10 was reported in Xiamen, China, however, an increase in cases was seen in 2015.

OBJECTIVES

We aimed to perform a retrospective molecular epidemiological analysis of HFMD associated with CV-A10 infections in Xiamen.

STUDY DESIGN

CV-A10 VP1 (n=41) capsid and full-length or near full-length genomes (n=14) were sequenced. Phylogenetic trees were constructed based on these sequences and other reference sequences and nucleotide and amino acid changes were characterized.

RESULTS

From 2009-2014, no laboratory-confirmed CV-A10 infections associated with severe cases were identified, however, in 2015, 39% (7/18) of severe HFMD cases were CV-A10 infections. Sequence analysis of severe and non-severe CV-A10 HFMD cases determined that severe cases predominantly clustered with an emerging clade E lineage A strain which contained 4 nucleotide changes in 5' UTR and 5 amino acid substitutions in structural and non-structural proteins.

CONCLUSIONS

The results indicate CV-A10 infection may be emerging as a new and major cause of severe HFMD and CV-A10 surveillance should be increased and considered in HFMD prevention and control strategies.

Epidemiological and aetiological characteristics of hand, foot, and mouth disease in Shijiazhuang City, Hebei province, China, 2009-2012

Large outbreaks of hand, foot, and mouth disease (HFMD) have repeatedly occurred in mainland of China since 2007. In this study, we investigated the epidemiological and aetiological characteristics of HFMD in Shijiazhuang City, one of the biggest northern cities of China. A total of 57,173 clinical HFMD cases, including 911 severe and 32 fatal cases, were reported in Shijiazhuang City during 2009–2012. The disease incidence peaked during March–July, with a small increase in the number of cases observed in November of each year. Seventeen potential HFMD-causing enterovirus serotypes were detected, with the most frequent serotypes being EV-A71 and CV-A16. CV-A10 was also a frequently detected causative serotype, and was associated with the second largest number of severe HFMD cases, following EV-A71. Phylogenetic analysis revealed that all EV-A71, CV-A16 and CV-A10 strains from Shijiazhuang City had co-evolved and co-circulated with those from other Chinese provinces. Our findings underscore the need for enhanced surveillance and molecular detection for HFMD, and suggest that EV-A71 vaccination may be an effective intervention strategy for HFMD prevention and vaccines against CV-A10 and CV-A16 are also urgently needed.

Two Genotypes of Coxsackievirus A2 Associated with Hand, Foot, and Mouth Disease Circulating in China since 2008

Coxsackievirus A2 (CV-A2) has been frequently detected and commonly associated with hand, foot, and mouth disease (HFMD) in China since 2008. However, limited sequences of CV-A2 are currently available. As a result, we have been focusing on the genetic characteristics of CV-A2 in the mainland of China during 2008-2015 based on national HFMD surveillance. In this study, 20 CV-A2 strains were isolated and phylogenetic analyses of the VP1 sequences were performed. Full-length genome sequences of two representative CV-A2 isolates were acquired and similarity plot and bootscanning analyses were performed. The phylogenetic dendrogram indicated that all CV-A2 strains could be divided into four genotypes (Genotypes A-D). The CV-A2 prototype strain (Fleetwood) was the sole member of genotype A. From 2008 to 2015, the CV-A2 strains isolated in China dispersed into two different genotypes (B and D). And the genotype D became the dominant circulating strains in China. Strains isolated in Russia and India from 2005 to 2011 converged into genotype C. Intertypic recombination occurred between the Chinese CV-A2 strains and other enterovirus-A donor sequences. This result reconfirmed that recombination is a common phenomenon among enteroviruses. This study helps expand the numbers of whole virus genome sequence and entire VP1 sequence of CV-A2 in the GenBank database for further researcher.

Epidemiology and etiology of hand, foot, and mouth disease in Fujian province, 2008-2014

Millions of cases of hand, foot, and mouth disease (HFMD) have been reported annually in mainland China since 2008. In this study, we investigated the epidemiology and etiology of an HFMD epidemic in Fujian province, which is located in subtropical southeastern China. Our study found similar epidemiological features of HFMD in southern areas of China, including seasonality and demographic distribution, as well as correlation between severity of illness and serotype. At least 22 serotypes of other enterovirus co-circulating with enterovirus 71 were found to belong to clade C4a, and those circulating with coxsackievirus A16 were associated with clades B1a and B1b.

Role and evolution trend of multiple enteroviruses in epidemic of hand, foot and mouth disease

There are a variety of enteroviruses (EV) that can cause hand, foot and mouth disease (HFMD), and the major pathogens include enterovirus 71 (EV71) and coxasckievirus A16 (CVA16). EV71 and CVA16 have attracted much attention for their high prevalence and pathogenicity, and disease surveillance and vaccine development are mainly concentrated on them. EV71 can cause serious harm to children with HFMD, especially the damage to the nervous system such as aseptic meningitis, brain stem encephalitis and paralytic disease, or even lead to death. However, in recent years, due to the epidemic of EV71 and CVA16, people have established an immune barrier through natural infection in a certain degree. Although there is no cross protection between types, the immune protection against the relevant type can persist for a long time. Thus, the number of HFMD cases caused by EV71 and CVA16 shows a decreasing trend, while the epidemic of HFMD caused by other EV exhibits an upward trend. Further studies found that non-EV71 and non-CVA16 EV are very complex, and there are also differences in EV prevalence each year, which makes the development, evolution and control of HFMD become complicated. At present, there is no enough attention paid to the sporadic virus in the HFMD epidemic, and a complete research system for non-EV71 and non-CVA16 EV has not formed. Therefore, it is necessary to strengthen the monitoring of multiple non-EV71 and non-CVA16 EV, further investigate their pathogenicity and genetic characteristics, and evaluate the relative frequency and biological hazard of infection. In this review, we summarize a variety of EV changes, molecular evolution, as well as typical epidemics, which may provide clues to the development of antiviral drugs and vaccines, and prevention and control of HFMD.

Inhibition of enterovirus VP4 myristoylation is a potential antiviral strategy for hand, foot and mouth disease

The Hand, Foot and Mouth Disease (HFMD) can result from infections by a plethora of human enteroviruses of the species Enterovirus A and B. These infections are highly contagious, resulting in regular outbreaks especially in the Asia-Pacific Region in the recent decade. Although this disease is generally a childhood affliction which manifests as a mild, febrile illness accompanied by the vesicles on the hands, feet and mouth, permanent morbidity or even fatality can result from severe forms of the disease in a subset of the infected patients. The N-terminal myristoylation signal (MGXXXS) of viral capsid protein VP4, one of the four viral structural proteins, is an extremely well conserved feature of enteroviruses, a potential antiviral target that may yield broad-spectrum inhibitors of HFMD. In this study, we have confirmed through the use of small interfering RNAs, human N-myristoyltransferase 1 plays an integral role in human Enterovirus 71 replication. Subsequent studies by inhibition of myristoylation using different myristic acid analogues elicited differential effects on the virus replication in human rhabdomyosarcoma cells. In particular, 2-hydroxymyristic acid specifically inhibited the cleavage between VP4 and VP2, part of the virion maturation process required to ensure infectivity of progeny virions while 4-oxatetradecanoic acid reduced the synthesis of viral RNA. These findings suggest that the requirement of a myristate moiety in viral structural protein precursor cleavage can serve as a viable antiviral target for further research.

MicroRNA and Pathogenesis of Enterovirus Infection

There are no currently available specific antiviral therapies for non-polio Enterovirus infections. Although several vaccines have entered clinical trials, the efficacy requires further evaluation, particularly for cross-strain protective activity. Curing patients with viral infections is a public health problem due to antigen alterations and drug resistance caused by the high genomic mutation rate. To conquer these limits in the development of anti-Enterovirus treatments, a comprehensive understanding of the interactions between Enterovirus and host cells is urgently needed. MicroRNA (miRNA) constitutes the biggest family of gene regulators in mammalian cells and regulates almost a half of all human genes. The roles of miRNAs in Enterovirus pathogenesis have recently begun to be noted. In this review, we shed light on recent advances in the understanding of Enterovirus infection-modulated miRNAs. The impacts of altered host miRNAs on cellular processes, including immune escape, apoptosis, signal transduction, shutdown of host protein synthesis and viral replication, are discussed. Finally, miRNA-based medication provides a promising strategy for the development of antiviral therapy.