Hand, foot and mouth disease in Guangdong, China, in 2013: new trends in the continuing epidemic

A screening study on the detection strain of Coxsackievirus A6: the key to evaluating neutralizing antibodies in vaccines

The increasing incidence of diseases caused by Coxsackievirus A6 (CV-A6) and the presence of various mutants in the population present significant public health challenges. Given the concurrent development of multiple vaccines in China, it is challenging to objectively and accurately evaluate the level of neutralizing antibody response to different vaccines. The choice of the detection strain is a crucial factor that influences the detection of neutralizing antibodies. In this study, the National Institutes for Food and Drug Control collected a prototype strain (Gdula), one subgenotype D1, as well as 13 CV-A6 candidate vaccine strains and candidate detection strains (subgenotype D3) from various institutions and manufacturers involved in research and development. We evaluated cross-neutralization activity using plasma from naturally infected adults (n = 30) and serum from rats immunized with the aforementioned CV-A6 strains. Although there were differences between the geometric mean titer (GMT) ranges of human plasma and murine sera, the overall trends were similar. A significant effect of each strain on the neutralizing antibody test (MAX/MIN 48.0 ∼16410.3) was observed. Among all strains, neutralization of the S112 strain by 15 different sera resulted in higher neutralizing antibody titers (GMTS112 = 132.0) and more consistent responses across different genotypic immune sera (MAX/MIN = 48.0). Therefore, S112 may serve as a detection strain for NtAb testing in various vaccines, minimizing bias and making it suitable for evaluating the immunogenicity of the CV-A6 vaccine.

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.

Establishment of the 1st Chinese national standard for CA6 neutralizing antibody

Coxsackievirus A6 (CA6) is one of the major causative agents of herpangina and hand-foot-mouth disease (HFMD). Since 2008, CA6 has circulated widely around the world. Especially in Asia-Pacific region CA6 had even replaced enterovirus A71 (EV71) and coxsackievirus A16 (CA16) as the main prevalent strain of HFMD. In the recent 10 years, monovalent and multivalent vaccines against CA6 have been researched and developed by manufacturers from China, Korea, and the USA. The neutralizing antibody titer is a key indicator for accurately evaluating immunogenicity of vaccine. However, so far, the World Health Organization international standard for CA6 neutralizing antibody has not been available. In order to meet the needs of evaluating the immunogenicity of vaccines against CA6, the first Chinese national standard for CA6 neutralizing antibody was established, which was conducted to ensure that methods used to measure the neutralizing antibody titers against CA6 are accurate, reliable, and comparable. Three lyophilized candidate standards (29#, 39# and 44#) were produced with 0.40 ml/vial from plasma samples donated by healthy individuals. The collaborative study showed that the 29# candidate standard could effectively minimize the variability in neutralization titers between labs and across challenging viruses of different genotypes (A, D1, and D3). Therefore, the 29# candidate sample was established as the first Chinese national standard for CA6 neutralizing antibody test. This standard has good long-term stability and was assigned a potency of 150 units per milliliter (U/ml) of CA6 neutralizing antibody. It will contribute to ensure uniformity of potency or activity of vaccines and potentially therapeutic antibody preparations.

Genetic characteristics of Coxsackievirus A6 from children with hand, foot and mouth disease in Beijing, China, 2017-2019

OBJECT

To investigate the evolution and genetic characteristics of Coxsackievirus A6 (CVA6) which acted as the predominant pathogen of hand, foot and mouth disease (HFMD) in children in Beijing, China, 2017-2019.

METHODS

Throat swab specimens were collected for general Enterovirus (EV), enterovirus A71 (EV-A71) and CVA16 detection by Real-time PCR. These general EV-positive samples were identified by semi-nested RT-PCR method and sequencing. The CVA6 VP1 gene and genome sequences were amplified and sequenced. The phylogenetic, variation and recombination analyses were performed.

RESULTS

A total of 1721 HFMD patients were enrolled in this study, with the male to female ratio of 1.62:1. The majority of cases were less than five years, which accounted for 73.50%. The overall detection rate of EV was 88.32% (1520/1721). A total of 8 EV types were identified, including CVA6 (55.86%), CVA16 (26.32%), EV-A71 (2.24%), CVA10 (2.04%), CVA4 (1.05%), CVA5 (0.59%), CVA2 (0.33%), and CVA8 (0.07%), while 175 (11.51%) EV were untyped. The main pathogen of HFMD was CVA6 from 2017 to 2018, while CVA6 and CVA16 were the main causative pathogens in 2019. The nucleotide and amino acid sequence identities of the 120 CVA6 complete VP1 gene sequences in this study were 91.2%-100.0% and 97.7%-100.0%, respectively. Compared with the prototype strain (Gdula) of CVA6, the nucleotide and amino acid sequence identities were 81.7%-84% and 94.7%-96.3%, respectively. The phylogenetic tree indicated that all 120 CVA6 sequences belonged to sub-genotype D3, while 119 CVA6 sequences belonged to evolutionary branch D3a, except one from 2017 belonged to D3b. Recombination analysis based on the complete genome sequences showed that potential multiple recombination may have occurred in 2B and 3D protein coding regions with EV-A114.

CONCLUSIONS

The main pathogens of HFMD were CVA6 and CVA16 in Beijing, China, 2017-2019; while these CVA6, as recombination strains, belonged to the D3a evolutionary branch.

Changing serotypes of hand, foot and mouth disease in Shanghai, 2017-2019

BACKGROUND

Hand, foot, and mouth disease (HFMD) is a common reportable infectious disease that is highly contagious among children in China. This study aimed to characterize the epidemics of HFMD and the serotypes of enterovirus (EV) after the introduction of EV-A71 vaccines in Shanghai, a city in Eastern China.

RESULTS

A total of 2271 HFMD cases were recruited in this study from May 2017 through October 2020. Among these cases, a male-to-female ratio of 1.6:1 was observed, and the cases were mainly in 1-4 years old (63.1%). Children of all ages had a relatively similar time span between the onset of HFMD and the initial medical visit (P = 0.5192). The cases were reported year-round with peaks in the summer (2018 and 2019) and fall (2017), which was consistent with previous epidemics of the reported HFMD cases in the Shanghai municipality. Among the specimens that tested positive for EV (n = 1855), CV-A6 was predominantly detected (71.1%), followed by CV-A16 (14.2%) and EV-A71 (7.0%). Notably, the number of HFMD cases infected with EV-A71 increased in 2019. Furthermore, 9.2% of the cases had comorbidities, mostly convulsion, bronchopneumonia, and pneumonia; however, they were not correlated with the EV serotypes. In addition, 31.2% (709/2271) of the cases were vaccinated with EV-A71 vaccines. The time span differed significantly between the time of vaccination and the onset of the disease across the groups based on whether the onset was before or after vaccination (P < 0.001).

CONCLUSIONS

CV-A6 is the predominant EV serotype in the epidemic of HFMD in Shanghai; in addition, CV-A16 and EV-A71 may be moderately prevalent. The changing trends in the presence of EV serotypes contributes to the periodicity of the HFMD epidemic. In addition, the minority of HFMD cases may have comorbidities, regardless of the EV serotype. The use of the EV-A71 vaccine has affected the HFMD epidemic. And serotype-specific protection by the EV-A71 vaccine may promote vaccination in children infected with EV-A71 compared to those infected with non-EV-A71 serotypes, which would further change the epidemic scenario of HFMD.

Transmissibility of hand, foot, and mouth disease in 97 counties of China

Hand, foot, and mouth disease (HFMD) is a serious disease burden in the Asia–Pacific region, including China. This study calculated the transmissibility of HFMD at county levels in Jiangsu Province, China, analyzed the differences of transmissibility and explored the possible influencing factors of its transmissibility. We built a mathematical model for seasonal characteristics of HFMD, estimated the effective reproduction number (R_eff), and compared the incidence rate and transmissibility in different counties using non-parametric tests, rapid cluster analysis and rank-sum ratio in 97 counties in Jiangsu Province from 2015 to 2020. The average daily incidence rate was between 0 and 4 per 100,000 people in Jiangsu Province from 2015–2020. The Quartile of R_eff in Jiangsu Province from 2015 to 2020 was 1.54 (0.49, 2.50). Rugao District and Jianhu District had the highest transmissibility according to the rank-sum ratio. R_eff generally decreased in 2017 and increased in 2018 in most counties, and the median level of R_eff was the lowest in 2017 (P < 0.05). The transmissibility was different in 97 counties in Jiangsu Province. The reasons for the differences may be related to the climate, demographic characteristics, virus subtypes, vaccination, hygiene and other infectious diseases.

Changing epidemiology of hand, foot, and mouth disease in China, 2013-2019: a population-based study

Background

Hand, foot, and mouth disease (HFMD) is an important public health problem. A monovalent EV-A71 vaccine was launched in China in 2016. Previous studies showed that inactivated monovalent EV-A71 vaccines were highly efficient against HFMD associated with EV-A71 but not against HFMD with other etiologies, leading to a hypothesis that the introduction of EV-A71 vaccines might change the pathogen spectrum and epidemiological trend of HFMD. In this study, we described for the first time the changing epidemiological characteristics of HFMD after the launch of the EV-A71 vaccine.

Methods

We extracted individual-based epidemiological data on HFMD cases reported to the Chinese Center for Disease Control and Prevention between January 2013 and December 2019. We described the changing epidemiological characteristics of HFMD before and after vaccine launch according to the distribution of diseases characteristics (demographic, temporal, and geographical) and evaluated the potential changes in risk factors of severe patients. All analyses were stratified by the phase before and after vaccine launch, and by enterovirus serotype.

Findings

During 2013-2019, 15,316,710 probable cases of HFMD were reported. Of these, 787,197 (5·1%) were laboratory confirmed and 76,982 (0·5%) were severe. After the launch of the EV-A71 vaccine, the median age of HFMD patients infected with EV-A71 increased from 2·24 years (IQR:1·43, 3·56) to 2·81 years (IQR:1·58, 4·01). The proportion of patients less than 3 years of age decreased while the proportion of patients 3-5 years of age increased. There was a large decrease (60·7%) in the proportion of severe cases as well as a decline (28·3%) in HFMD patients infected with EV-A71. After the launch of the EV-A71 vaccine, the severe illness rate and mortality rate of HFMD patients in all age groups has decreased sharply, 62·20% and 83·78% respectively. The timing of the HFMD epidemic peak was delayed (1-2 months) . After the launch of EV-A71 vaccine, the risk of becoming a severe case for EV-A71 serotype was decreased, whereas that risk was instead increased for CV-A16 (from 0·17 (95% CI:0·16, 0·18) to 0·23 (95% CI:0·21, 0·25)) and other enterovirus compared to EV-A71 (from 0·38 (95% CI:0·37, 0·39) to 0·58 (95% CI:0·56, 0·61)). The longer the time from onset to diagnosis, the higher was the risk of being a severe case, but the effect size was decreased.

Interpretation

The introduction of the EV-A71 vaccine has effectively reduced the proportion of severe HFMD cases and mortality, but changes to the dominant serotypes should be closely monitored. Development of multivalent vaccines to avoid an increased case burden due to other enteroviruses is greatly needed.

Funding

This research was supported by the National Natural Science Foundation of China (81973102, 81773487), Public Health Talents Training Program of Shanghai Municipality (GWV-10.2-XD21), the 5th Three-year Action Program of Shanghai Municipality for Strengthening the Construction of Public Health System (GWV-10.1-XK05), the Major Project of Scientific and Technical Winter Olympics from National Key Research and Development Program of China (2021YFF0306000), 13th Five-Year National Science and Technology Major Project for Infectious Diseases (2018ZX10725-509) and Key projects of the PLA logistics Scientific research Program (BHJ17J013).

Metabolomic characteristics of hand-foot-mouth disease facilitate discovery and diagnosis of pathogeny

BACKGROUND

Hand-foot-mouth disease (HFMD) is a significant public health concern, especially in Asia-Pacific countries. Its diagnosis mainly depends on clinical symptoms. It is easy to miss the source of infection and best treatment period. This research aims to provide a tool for its early clinical diagnosis and for predicting the possibility of complications.

METHODS

The serum samples of 39 HFMD children and 36 healthy children were collected for clinical testing and ¹ H-NMR spectroscopy. Metabolomic analyses were performed to obtain the metabolic differences between the HFMD and healthy children and to speculate on the pathogenesis of HFMD.

RESULTS

Thirty-nine children were divided into severe cases and mild cases. Severe cases demonstrated more obvious inflammatory responses, but no metabolic difference was observed between the severe and mild cases. The metabolic differences between HFMD and healthy children were noticeable. Ten differential metabolites were screened out as the potential biomarkers for HFMD, and seven disturbed metabolic pathways responsible for HFMD were affected by inflammation, impaired intestinal absorptive function, and immune response.

CONCLUSIONS

Our results will provide a complementary tool for the early diagnosis of HFMD and potential ideas for later treatment.

Molecular surveillance of coxsackievirus A16 in southern China, 2008-2019

A national surveillance system on hand, foot, and mouth disease (HFMD) was launched in 2008 in China. Since then, millions of HFMD cases have been reported each year, with enterovirus A71 (EV-A71), coxsackievirus A16 (CV-A16), and coxsackievirus A6 (CV-A6) as the major causative pathogens. Long-term surveillance of viral infection rates and genetic changes is essential for understanding the disease epidemiology pattern. Here, we analyzed molecular surveillance data on CV-A16 covering a period of 12 years (2008-2019) in Guangdong, China, one of the regions reporting the largest number of HFMD cases. Full VP1 sequences of 456 strains were determined to examine the genetic diversity and changes in the distribution of CV-A16 variants. Our study revealed an irregular pattern of CV-A16 infections in Guangdong. Different from the cyclic epidemics observed in some Asia-Pacific regions, there was a continuously high CV-A16 infection rate from 2008 to 2014, and after a period of lower epidemic activity in 2015-2017, an upsurge of CV-A16 infection was observed in 2018-2019. Cocirculation of subgenotypes B1a and B1b was observed, but while subgenotype B1a was predominant from 2008 to 2012, it appears to have been replaced by B1b, which has circulated as the predominant subgenotype since 2013. Phylogenetic analysis showed that most of the circulating CV-A16 strains are endemic, with occasional transmission between neighboring regions. The re-emergence of B1a in 2016-2019 in Guangdong was likely the result of introduction(s) from Southeast Asia. These results highlight the importance of continuous molecular surveillance from different areas, which will improve our understanding of the origin of the epidemic and facilitate the development of strategies for HFMD disease control.

A kindergarten-based, family-involved intervention to improve children's hand hygiene behavior: A cluster-randomized controlled trial

OBJECTIVE

The present study determined the feasibility and initial efficacy of a kindergarten-based, family-involved intervention in improving children's hand hygiene (HH) behaviors.

DESIGN

A cluster-randomized controlled trial was performed, with a cluster defined as a kindergarten class.

SAMPLE

Participants were recruited from 20 classes in six kindergartens. A total of 289 children and their families were enrolled in the intervention group, and 293 children and their families were enrolled in the control group.

MEASUREMENTS

HH behavior and a related knowledge survey, as well as data on absences due to infection, were collected.

INTERVENTION

An 8-week training session on HH for children and an education program combining a seminar and WeChat groups for parents were provided to participants in the intervention group.

RESULTS

Two HH behaviors of children, namely, HH after playing outside and 7-stage HH compliance, were significantly different between the two groups after the intervention. The two HH behaviors and knowledge of infections of parents/legal guardians in the intervention group were better than those in the control group after the intervention. The number of absences due to infections in children was lower in the intervention group than in the control group.

CONCLUSIONS

Kindergarten-based, family-involved interventions effectively improved the HH behavior of kindergarten children and decreased absences due to infections.

Molecular epidemiology of coxsackievirus A16 circulating in children in Beijing, China from 2010 to 2019

BACKGROUND

Coxsackievirus A16 (CVA16) is one of the major etiological agents of hand, foot and mouth disease (HFMD). This study aimed to investigate the molecular epidemiology and evolutionary characteristics of CVA16.

METHODS

Throat swabs were collected from children with HFMD and suspected HFMD during 2010-2019. Enteroviruses (EVs) were detected and typed by real-time reverse transcription-polymerase chain reaction (RT-PCR) and RT-PCR. The genotype, evolutionary rate, the most recent common ancestor, population dynamics and selection pressure of CVA16 were analyzed based on viral protein gene (VP1) by bioinformatics software.

RESULTS

A total of 4709 throat swabs were screened. EVs were detected in 3180 samples and 814 were CVA16 positive. More than 81% of CVA16-positive children were under 5 years old. The prevalence of CVA16 showed obvious periodic fluctuations with a high level during 2010-2012 followed by an apparent decline during 2013-2017. However, the activities of CVA16 increased gradually during 2018-2019. All the Beijing CVA16 strains belonged to sub-genotype B1, and B1b was the dominant strain. One B1c strain was detected in Beijing for the first time in 2016. The estimated mean evolutionary rate of VP1 gene was 4.49 × 10^-3 substitution/site/year. Methionine gradually fixed at site-23 of VP1 since 2012. Two sites were detected under episodic positive selection, one of which (site-223) located in neutralizing linear epitope PEP71.

CONCLUSIONS

The dominant strains of CVA16 belonged to clade B1b and evolved in a fast evolutionary rate during 2010-2019 in Beijing. To provide more favorable data for HFMD prevention and control, it is necessary to keep attention on molecular epidemiological and evolutionary characteristics of CVA16.

Emergence of a non vaccine-cognate enterovirus A71 genotype C1 in mainland China

BACKGROUND

EV-A71 is a common causative agent of hand foot and mouth disease. In mainland China, EV-A71 subgenotype C4 has been the sole circulating genotype since 2008, and was used in the production of multiple licensed vaccines. Here, we report the first detection EV-A71 C1 strains in China.

METHODS

Full genomic sequence were obtained. The origin of the EV-A71 C1 strains were tracked down by Bayesian inferences. Recombination was analyzed using Simplot program. And the antigenicity were tested using the microneutralization test.

RESULTS

The C1-GD2019 shared high identity with the C1-like lineage recently identified in Europe and was introduced into Guangdong in 2018-2019. Close genetic relatedness between the C1-GD2019 and Europe C1-like strains were observed except for the 3D-3'UTR region. The late showed high similarity with CVA genomes. Antigenic variance was found. The C1-GD2019 could not be effectively neutralized by EV-A71 C4a neutralizing antibody positive samples.

CONCLUSION

This is the first report of EV-A71 subgenotype C1 isolated in China. It is a recombinant strain originating from C1-like strains recently identified in Europe and CVA strains. The different antigenicity between the C1 strains and C4a vaccine strains highlighted the importance on closely monitoring the EV-A71 C1 strains in China.

Estimation of the reproduction number and identification of periodicity for HFMD infections in northwest China

Repeated outbreaks of Hand, foot and mouth disease (HFMD) infections have been observed in recent decades and dominated by various enteroviral serotypes. In particular, enterovirus 71 (EV-A71), coxsackievirus A16 (CV-A16) and coxsackievirus A6 (CV-A6) dominated the prevalence of HFMD infections alternatively in recent years with various outbreak sizes in Baoji, a city of Shaanxi Province in Northwest China. Estimating the reproduction number for various enteroviruses serotypes in northwest China (north temperate zone) and identification of cyclicity of HFMD infections are therefore an issue of great importance for future epidemics prediction and control. The basic/effective reproduction numbers for EV-A71, CV-A16 and CV-A6 were estimated based on daily new cases in 2010, 2011 and 2018, respectively, in which the corresponding pathogen dominated the epidemic. Two different methods based on serial interval were adopted and the basic reproduction number were estimated to be in the range of (1.33, 1.46) for CV-A16, (1.20, 1.29) for EV-A71, and (1.38, 1.59) for CV-A6, respectively. The estimated daily effective reproduction numbers significantly fluctuated before June or after July but varied mildly in (0.5,2) in around June to July for three serotypes. The weekly effective reproduction number for HFMD was estimated based on weekly new cases from year 2010 to 2018, and in most years it peaked in the range of (1.6,2.0) in February to March as well as in the range of (1.0,1.2) in September to October. The wavelet analysis based on the time series of HFMD cases from 2008 to 2018 showed obvious annual and semi-annual cyclicity, while the inter-annual cycles are infeasible. In this study we found that CV-A6 shows the greatest transmission ability among these three pathogens while EV-A71 exhibits the weakest ability of transmission, and moreover, the estimated values of basic reproduction number in northwest China are lower than those in Singapore, Hongkong and Guangdong, which may be due to different climatic circumstances.

Hand-foot-and-mouth disease in uruguay: Coxsackievirus A6 identified as causative of an outbreak in a rural childcare center

To know the epidemiological context of hand-foot-and-mouth disease (HFMD) in a region of Uruguay and to identify the Enterovirus responsible for an outbreak in a rural childcare center in 2018. Swab samples from skin lesions and/or stools samples were collected from children suffering HFMD during an outbreak in a rural childcare center. Samples were subject to viral RNA extraction and reverse-transcription polymerase chain reaction towards VP1 coding segment, to identify the Enterovirus type by sequencing and phylogenetic analysis. Total of 149 cases of HFMD affecting 98 boys and 51 girls were reported in Salto Province-Uruguay in 2018. Total 60% of the cases were originated from outbreaks, which occurred in ten educative and childcare institutions from both urban and rural areas. Coxsackievirus-6 (CV-A6) was identified as responsible for one of the rural outbreaks. Uruguayan strains were more related to strains reported in Russia, Turkey, and Germany (2014-2017) than to strains reported in Brazil and Argentina from 2015 to 2016. This is the first report of CV-A6-associated HFMD in Uruguay, evidencing a wide geographic range of the virus in the Latin American region. Our report also warns about CV-A6-associated HFMD during winter, contrarily to most reports that register HFMD during summer and fall seasons.

The surveillance of the epidemiological and serotype characteristics of hand, foot, mouth disease in Neijiang city, China, 2010-2017: A retrospective study

Hand, foot, and mouth disease (HFMD) is well recognized as one of the major threats to children’s health globally. The increasing complexity of the etiology of HFMD still challenges disease control in China. There is little surveillance of the molecular epidemiological characteristics of the enteroviruses (EVs) that cause HFMD in Neijiang city or the Sichuan Basin area in Southwest China. In this study, demographic and epidemiological information for 14,928 probable HFMD cases was extracted and analyzed to describe the epidemic features of HFMD in Neijiang city from Jan 2010 to Dec 2017. The swab samples of select probable HFMD cases from 2012 to 2017 were tested by reverse transcription (RT) real-time PCR to identify the serotype distribution of EVs, and 110 randomly selected RT-real-time PCR positive samples were then amplified and analyzed for the VP1 or VP4 regions of EVs to further analyze the phylogenetic characteristics of the circulating strains in this area. The eight-year average annual incidence was 49.82 per 100,000 in Neijiang. The incidence rates varied between 19.51 and 70.73 per 100,000, demonstrating peaks of incidence in even-number years (2012, 2014 and 2016). The median age of the probable cases was 27 months and the interquartile range (25^th to 75^th percentile) of ages for the probable HFMD cases was between 14 and 42 months. The male-to-female ratio of the probable HFMD cases was 1.47:1, and scattered children were the major population classification (81.7%). Two epidemic peaks were observed: one major peak between April and July and the other lesser peak between October and December. Of 6513 probable cases tested with RT-real-time PCR, 4015 (61.6%) were positive for enterovirus with the serotype distribution as follows: EV71+, 30.1% (n = 1210); CV-A16+, 28.7% (n = 1154) and a sole pan-enterovirus+, 41.1% (n = 1651). A total of 91 cases (82.7%, 91/110) were successfully amplified and underwent phylogenetic analysis: all EV71+ cases were C4a serotype (n = 23/30); all CV-A16+ cases were B2b serotype (n = 24/30); of 42 sole pan-enterovirus+ samples, 20 were CV-A6, 14 were CV-A10 and the rest within this group were CV-A4 (n = 4), CV-A8 (n = 2), CV-A9 (n = 1) and CV-B3 (n = 1). Our findings provide important evidence that aids the improvement of strategies for vaccination against HFMD and comprehensive disease control in China.

Molecular characteristic analysis for the VP1 region of coxsackievirus A6 strains isolated in Jiujiang area, China, from 2012 to 2013

BACKGROUND

Enterovirus 71 (EV-A71) and Coxsackievirus A16 (CV-A16) are the most common causative agents causing hand, foot, and mouth disease (HFMD). However, coxsackievirus A6 (CV-A6), previously largely ignored, became the predominant pathogen in China in 2012. The objective of this study is to investigate the genetic characteristics and molecular epidemiology of HFMD caused by CV-A6 to guide the diagnosis and treatment of the disease, as well as disease prevention.

MATERIAL AND METHODS

A total of 138 suspected HFMD cases were enrolled in this study and analyses based on complete VP1 nucleotide sequences were performed to determine the evolutionary trajectory of emerging CV-A6.

RESULTS

Among 138 samples in Jiujiang, 125 (90.58%) were positive for enterovirus, the most frequently presented serotypes were CV-A6 (77, 61.60%), CV-A16 (28, 22.40%), EV-A71 (6, 4.80%) and untyped enteroviruses (14, 11.20%). Seventy-seven CV-A6 positive specimens were analyzed for the complete VP1 sequences by sequencing and 36 representative isolates were selected to perform nucleotide sequence similarity analysis. The results showed that 36 strains isolated from HFMD patients were clustered closely to the mainland China and were far from prototype strain CV-A6/Gdula (AY421764) and other international subtypes. Moreover, phylogenetic analysis of the VP1 gene revealed that 36 circulating strains were not significantly concentrated in one branch, but were widely distributed in each branch.

CONCLUSIONS

Continuous surveillance of HFMD etiological agents other than EV-A71 and CV-A16 is necessary. CV-A6 is emerging as the most common pathogen causing HFMD. Closely monitoring the magnitude and trend of CV-A6 epidemic and the trend of pathogenic spectrum changes can provide scientific basis for this disease prevention and control to the department of disease control.

Epidemiologic features of enterovirus associated with hand, foot and mouth disease in 2013 and 2014 in Shenzhen, China

Hand, foot and mouth disease (HFMD) is responsible for a heavy economic and social burden in the Asia-Pacific region. Previous studies have shown that coxsackievirus A6 (CVA6) and coxsackievirus A10 (CVA10) have become the predominant agents of HFMD in mainland China in recent years, replacing enterovirus 71 (EV71) and coxsackievirus A16 (CVA16), although it is unclear if this is consistent throughout China. In this study, samples from 253 HFMD cases were collected in Shenzhen, China, from May 2013 through April 2014 to identify the etiological agent of HFMD. In total, 64.8% (164/253) of HFMD cases were enterovirus positive, in which 81.1% (133/164) were determined to be CVA6. The phylogenetic tree of the partial viral protein 1 sequence showed that the CVA6 isolates were divided into four clusters (Clusters A to D), and cluster D was further divided into four sub-clusters (Clusters D1 to D4). The 133 CVA6 samples isolated in our study were classified into cluster D4, in which the first identified sequence was isolated in Shenzhen in 2008. This study demonstrated that the CVA6 cluster D4, which is predominantly circulating in HFMD in mainland China, may have originated from a local strain identified in 2008 in Shenzhen.

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.

Emerging Coxsackievirus A6 Causing Hand, Foot and Mouth Disease, Vietnam

Hand, foot and mouth disease (HFMD) is a major public health issue in Asia and has global pandemic potential. Coxsackievirus A6 (CV-A6) was detected in 514/2,230 (23%) of HFMD patients admitted to 3 major hospitals in southern Vietnam during 2011–2015. Of these patients, 93 (18%) had severe HFMD. Phylogenetic analysis of 98 genome sequences revealed they belonged to cluster A and had been circulating in Vietnam for 2 years before emergence. CV-A6 movement among localities within Vietnam occurred frequently, whereas viral movement across international borders appeared rare. Skyline plots identified fluctuations in the relative genetic diversity of CV-A6 corresponding to large CV-A6–associated HFMD outbreaks worldwide. These data show that CV-A6 is an emerging pathogen and emphasize the necessity of active surveillance and understanding the mechanisms that shape the pathogen evolution and emergence, which is essential for development and implementation of intervention strategies.

Epidemic pattern of hand-foot-and-mouth disease in Xi'an, China from 2008 through 2015

Background

Hand, foot and mouth disease (HFMD) is an infectious disease caused by enteroviruses that has a severely impair for those high incidence countries such as China.The current study aimed to investigate the epidemic pattern of HFMD by time and region in Northwestern China.

Methods

All reported HFMD cases from 2008 to 2015 were collected from local Disease Control and Prevention.The HFMD was diagnosed in accordance with the guidebook provided by the National Health and Family Planning Commission of the People’s Republic of China.

Results

A total of 154,869 cases of probable HFMD were reported. The overall incidence of HFMD has been increased from 91.68 per 100/000 in 2008 to 335.64 per 100/000 in 2015.The case mortality is decreased from 0.014 per100/000 to 0.011 per 100/000 during the time period. Most HFMD (93.82%) occurred in children younger than 5 years. The seasonal peak of HFMD infections occurred in April–July and September–November and Central regions of Xi’an city were the major locations of the clusters (incidence rate 245.75/100,000; relative risk 1.19, P < 0.01). EVA71 was the predominant enterovirus serotype, accounting for 50.0% of all reported HFMD cases since 2011.The most susceptible group infected by HFMD was children younger than 5 years, especially boys.

Conclusions

Incidence of HFMD has been increasing in the past few years, however, the case fatality is decreasing. Season and region shall be considered as influence factors in the prevention of HFMD.

Population based hospitalization burden of laboratory-confirmed hand, foot and mouth disease caused by multiple enterovirus serotypes in Southern China

BACKGROUND

Hand, foot and mouth disease (HFMD) is spread widely across Asia, and the hospitalization burden is currently not well understood. Here, we estimated serotype-specific and age-specific hospitalization rates of HFMD in Southern China.

METHODS

We enrolled pediatric HFMD patients admitted to 3/3 county-level hospitals, and 3/23 township-level hospitals in Anhua county, Hunan (CN). Samples were collected to identify enterovirus serotypes by RT-PCRs between October 2013 and September 2016. Information on other eligible, but un-enrolled, patients were retrospectively collected from the same six hospitals. Monthly numbers of all-cause hospitalizations were collected from each of the 23 township-level hospitals to extrapolate hospitalizations associated with HFMD among these.

RESULTS

During the three years, an estimated 3,236 pediatric patients were hospitalized with lab-confirmed HFMD, and among these only one case was severe. The mean hospitalization rate was 660 (95% CI: 638-684) per 100,000 person-years for lab-confirmed HFMD, with higher rates among CV-A16 and CV-A6 associated HFMD (213 vs 209 per 100,000 person-years), and lower among EV-A71, CV-A10 and other enterovirus associated HFMD (134, 39 and 66 per 100,000 person-years respectively, p<0.001). Children aged 12-23 months had the highest hospitalization rates (3,594/100,000 person-years), followed by those aged 24-35 months (1,828/100,000 person-years) and 6-11 months (1,572/100,000 person-years). Compared with other serotypes, CV-A6-associated hospitalizations were evident at younger ages.

CONCLUSIONS

Our study indicates a substantial hospitalization burden associated with non-severe HFMD in a rural county in southern China. Future mitigation policies should take into account the disease burden identified, and optimize interventions for HFMD.

Molecular epidemiology of coxsackievirus A6 circulating in Hong Kong reveals common neurological manifestations and emergence of novel recombinant groups

BACKGROUND

Coxsackievirus A6 (CV-A6) represents the predominant enterovirus serotype in Hong Kong, but its epidemiology in our population was unknown.

OBJECTIVES

To examine the clinical and molecular epidemiology of CV-A6 and detect emerging recombinant strains in Hong Kong.

STUDY DESIGN

Nasopharyngeal aspirates (NPAs) from patients with febrile or respiratory illness were subject to RT-PCR for CV-A6 and sequencing of 5'-NCR and VP1. CV-A6-positive samples were further subject to 2C and 3D gene sequencing. Complete genome sequencing was performed on potential recombinant strains.

RESULTS

Thirty-six (0.35%) NPAs were positive for CV-A6 by 5'-NCR RT-PCR and sequencing, 28 of which confirmed by partial VP1 gene sequencing. Among the 28 patients (mainly young children) with CV-A6 infection, hand-foot-and-mouth disease (HFMD) (43%), herpangina (18%) and tonsillitis (11%) were the most common diagnoses. Seven (25%) patients had neurological manifestations, including febrile seizures, encephalitis and meningitis. VP1 gene analysis showed that 24 CV-A6 strains circulating in Hong Kong belonged to genotype D5, while 4 strains belonged to D4. Further 2C and 3D gene analysis revealed eight potential recombinant strains. Genome sequencing of five selected strains confirmed four recombinant strains: HK459455/2013 belonging to recombination group RJ arisen from CV-A6/CV-A4, HK458288/2015 and HK446377/2015 representing novel group RL arisen from CV-A6/CV-A4, and HK462069/2015 representing novel group RM arisen from CV-A6/EV-A71. Recombination breakpoints located at 3D were identified in the latter three recombinant strains, with HK462069/2015 (from a child with encephalitis) having acquired 3D region from EV-A71.

CONCLUSIONS

We identified novel recombinant CV-A6 strains in Hong Kong, with 3D being a common recombination site.

Epidemiology of hand, foot and mouth disease in China, 2008 to 2015 prior to the introduction of EV-A71 vaccine

Hand, foot and mouth disease (HFMD) is usually caused by several serotypes from human enterovirus A species, including enterovirus 71 (EV-A71) and coxsackievirus A16 (CV-A16). Two inactivated monovalent EV-A71 vaccines have been recently licensed in China and monovalent CV-A16 vaccine and bivalent EV-A71 and CV-A16 vaccine are under development. Methods: Using notifications from the national surveillance system, we describe the epidemiology and dynamics of HFMD in the country, before the introduction of EV-A71 vaccination, from 2008 through 2015. Results: Laboratory-identified serotype categories, i.e. CV-A16, EV-A71 and other enteroviruses, circulated annually. EV-A71 remained the most virulent serotype and was the major serotype for fatal cases (range: 88.5–95.4%) and severe cases (range: 50.7–82.3%) across years. Except for 2013 and 2015, when other enteroviruses were more frequently found in mild HFMD (48.8% and 52.5%), EV-A71 was more frequently detected from mild cases in the rest of the years covered by the study (range: 39.4–52.6%). The incidence rates and severity risks of HFMD associated with all serotype categories were the highest for children aged 1 year and younger, and decreased with increasing age. Discussion/conclusion: This study provides baseline epidemiology for evaluation of vaccine impact and potential serotype replacement.

Divergent Pathogenic Properties of Circulating Coxsackievirus A6 Associated with Emerging Hand, Foot, and Mouth Disease

Coxsackievirus A6 (CV-A6) is an emerging pathogen associated with hand, foot, and mouth disease (HFMD). Its genetic characterization and pathogenic properties are largely unknown. Here, we report 39 circulating CV-A6 strains isolated in 2013 from HFMD patients in northeast China. Three major clusters of CV-A6 were identified and related to CV-A6, mostly from Shanghai, indicating that domestic CV-A6 strains were responsible for HFMD emerging in northeast China. Four full-length CV-A6 genomes representing each cluster were sequenced and analyzed further. Bootscanning tests indicated that all four CV-A6-Changchun strains were most likely recombinants between the CV-A6 prototype Gdula and prototype CV-A4 or CV-A4-related viruses, while the recombination pattern was related to, yet distinct from, the strains isolated from other regions of China. Furthermore, different CV-A6 strains showed different capabilities of viral replication, release, and pathogenesis in a mouse model. Further analyses indicated that viral protein 2C contributed to the diverse pathogenic abilities of CV-A6 by causing autophagy and inducing cell death. To our knowledge, this study is the first to report lethal and nonlethal strains of CV-A6 associated with HFMD. The 2C protein region may play a key role in the pathogenicity of CV-A6 strains.IMPORTANCE Hand, foot, and mouth disease (HFMD) is a major and persistent threat to infants and children. Besides the most common pathogens, such as enterovirus A71 (EV-A71) and coxsackievirus A16 (CV-A16), other enteroviruses are increasingly contributing to HFMD. The present study focused on the recently emerged CV-A6 strain. We found that CV-A6 strains isolated in Changchun City in northeast China were associated with domestic origins. These Changchun viruses were novel recombinants of the CV-A6 prototype Gdula and CV-A4. Our results imply that measures to control CV-A6 transmission are urgently needed. Further analyses revealed differing pathogenicities in strains isolated in a neonatal mouse model. One of the possible causes has been narrowed down to the viral protein 2C, using phylogenetic studies, viral sequences, and direct tests on cultured human cells. Thus, the viral 2C protein is a promising target for antiviral drugs to prevent CV-A6-induced tissue damage.

Epidemiological surveillance of hand, foot and mouth disease in Shanghai in 2014-2016, prior to the introduction of the enterovirus 71 vaccine

Hand, foot, and mouth disease (HFMD) is mainly epidemic in China and Southeast Asian countries. A novel enterovirus 71 vaccine has been available in China for preventing severe HFMD since 2016. Knowledge of the dynamic epidemiology of HFMD in different regions is necessary for appropriate intervention strategies. This study focused on the citywide surveillance data on the epidemiology and etiology of HFMD in Shanghai during 2014–2016. In these 3 years, the total numbers of reported HFMD cases were 65,018, 39,702, and 57,548, respectively; the numbers of severe cases (case-severity ratios) were 248 (0.38%), 35 (0.09%), and 59 (0.10%), respectively. Children <6 years old accounted for 86.65% to 89.34% of HFMD cases and 91.53 to 97.14% of severe cases. EV-A71 caused all three fatal cases. In severe cases, the detection rate of EV-A71 was 77.82% in 2014, 100% in 2015 and 98.31% in 2016. In uncomplicated inpatient cases, the detection rates of EV-A71, CV-A16, CV-A6, and CV-A10 were, respectively, 43.40, 22.10, 30.73, and 1.89% in 2014; 28.52, 6.46, 53.61, and 7.98% in 2015; and 31.79, 14.15, 44.55, and 4.64% in 2016. In mild community cases, the detection rates of EV-A71, CV-A16, CV-A6, and CV-A10 were, respectively, 25.78, 41.64, 22.93, and 1.78% in 2014; 17.41, 21.23, 50.99, and 3.15% in 2015; and 18.92, 27.84, 45.11, and 1.64% in 2016. Among the cluster outbreaks, the most common pathogen was CV-A16 in 2014 (50.69%) and 2015 (38.10%) and CV-A6 in 2016 (36.30%). These findings show that HFMD outbreaks remained at a high level in Shanghai during 2014–2016. CV-A6 was emerging as the most common pathogen causing HFMD.

Epidemiological Characteristics and Spatial-Temporal Distribution of Hand, Foot, and Mouth Disease in Chongqing, China, 2009-2016

(1) Objective: Even with licensed vaccine for enterovirus 71 (EV71) put into market in 2016 in China, hand, foot, and mouth disease (HFMD) is still a threat for children’s health in Chongqing. We described the epidemiological characteristics and spatial–temporal patterns of HFMD in Chongqing from 2009 to 2016, in order to provide information and evidence for guiding public health response and intervention. (2) Methods: We retrieved the HFMD surveillance data from January 2009 to December 2016 from “National Disease Reporting Information System”, and then analyzed demographic and geographical information integrally. Descriptive analysis was conducted to evaluate the epidemic features of HFMD in Chongqing. The spatial–temporal methods were performed to explore the clusters at district/county level. (3) Results: A total of 276,207 HFMD cases were reported during the study period (total population incidence: 114.8 per 100,000 per year), including 641 severe cases (129 deaths). The annual incidence of HFMD sharply increased in even-numbered years, but remained stable or decreased in odd-numbered years. A semiannual seasonality was observed during April to July, and October to December in each year. The male-to-female ratios of the mild and severe cases were 1.4:1 and 1.5:1, with the median age of 2.3 years and 1.9 years, respectively. More than 90% of the cases were children equal to and less than 5 years old. High-incidence clustered regions included the main urban districts and northeast regions according to incidence rates comparison or space–time cluster analysis. A total of 19,482 specimen were collected from the reported cases and 13,277 (68.2%) were positive for enterovirus. EV71 was the major causative agent for severe cases, while other enteroviruses were the predominant serotype for mild cases. (4) Conclusions: The characteristics of HFMD in Chongqing exhibited a phenomenon of increasing incidence in two-year cycles and semiannual seasonality in time distribution. Children ≤5 years old, especially boys, were more affected by HFMD. EV71 was the major causative agent for severe cases. We suggest initiating mass EV71 vaccination campaigns among children aged 6 months to 5 years in Chongqing, especially in the main urban districts and northern regions, in order to reduce case fatality, and take integrated measurements for controlling and preventing HFMD attributed to other enteroviruses.

Epidemiological characteristics of hand, foot, and mouth disease in Shandong, China, 2009-2016

In the past decade, hand, foot, and mouth disease (HFMD) has posed a serious threat to childhood health in China; however, no epidemiological data from large HFMD epidemics have been described since 2013. In the present study, we described the epidemiological patterns of HFMD in Shandong province during 2009–2016 from a large number of symptomatic cases (n = 839,483), including >370,000 HFMD cases since 2013. Our results revealed that HFMD activity has remained at a high level and continued to cause annual epidemics in Shandong province from 2013 onwards. Although the incidence rate was significantly higher in urban areas than in rural areas, no significantly higher case-severity and case-fatality rates were found in urban areas. Furthermore, the seventeen cities of Shandong province could be classified into three distinct epidemiological groups according to the different peak times from southwest (inland) to northeast (coastal) regions. Notably, a replacement of the predominant HFMD circulating agent was seen and non-EVA71/Coxsackievirus A16 enteroviruses became dominant in 2013 and 2015, causing approximately 30% of the severe cases. Our study sheds light on the latest epidemiological characteristics of HFMD in Shandong province and should prove helpful for the prevention and control of the disease in Shandong and elsewhere.

Epidemiological and genetic analysis concerning the non-enterovirus 71 and non-coxsackievirus A16 causative agents related to hand, foot and mouth disease in Anyang city, Henan Province, China, from 2011 to 2015

Enterovirus 71 (EV-A71) and coxsackievirus A16 (CV-A16) are major pathogens of hand, foot, and mouth disease (HFMD) and have been associated with consecutive outbreaks of HFMD in China over the past years. Although several other human enteroviruses (HEVs) have also acted as causative agents of HFMD, published information on their roles in the prevalence of HFMD is limited. This study was conducted to reveal the characteristics of the pathogenic spectrum and molecular epidemiology of the non-EV-71 and -CV-A16 HEVs in Anyang City, which is located in north-central China and has a population of five million. From 2011 to 2015, 2270 samples were collected from HFMD patients (3.89 ± 1.06 years of age), and 1863 HEV-positive samples, including 524 samples with 23 non-EV-71 and non-CV-A16 serotypes, were identified. Based on the nucleotide sequence of the VP1 gene, 6 common non-EV-71 and non-CV-A16 HEVs, including coxsackievirus A2, A6, A10, A14, B2, and B5, were studied to determine their phylogenies and selective pressures. Phylogenetic analyses revealed a high level of genetic divergence and a pattern of lineage replacement over time in Mainland China. Selective pressure analyses showed that purifying selection was predominant in the evolution of the VP1 gene, whereas positive selection acted on individual codons. Overall, non-EV-71 and non-CV-A16 HEVs were important constituents of the pathogenic spectrum of HFMD in Anyang City during 2011-2015. Some of these HEVs with complex and active phylogenies represent a potential threat to public health, suggesting that long-term monitoring of these pathogens should be implemented to prevent HFMD outbreaks.

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.

A Neonatal Murine Model of Coxsackievirus A6 Infection for Evaluation of Antiviral and Vaccine Efficacy

Hand, foot, and mouth disease (HFMD) is a global health concern. Family Picornaviridae members, particularly enterovirus A71 (EVA71) and coxsackievirus A16 (CVA16), are the primary etiological agents of HFMD; however, a third enterovirus A species, CVA6, has been recently associated with epidemic outbreaks. Study of the pathogenesis of CVA6 infection and development of antivirals and vaccines are hindered by a lack of appropriate animal models. We have developed and characterized a murine model of CVA6 infection that was employed to evaluate the antiviral activities of different drugs and the protective efficacies of CVA6-inactivated vaccines. Neonatal mice were susceptible to CVA6 infection via intramuscular inoculation, and the susceptibility of mice to CVA6 infection was age and dose dependent. Five-day-old mice infected with 10^5.5 50% tissue culture infective doses of the CVA6 WF057R strain consistently exhibited clinical signs, including reduced mobility, lower weight gain, and quadriplegia with significant pathology in the brain, hind limb skeletal muscles, and lungs of the infected mice in the moribund state. Immunohistochemical analysis and quantitative reverse transcription-PCR (qRT-PCR) analyses showed high viral loads (11 log₁₀/mg) in skeletal muscle, and elevated levels of interleukin-6 (IL-6; >2,000 pg/ml) were associated with severe viral pneumonia and encephalitis. Ribavirin and gamma interferon administered prophylactically diminished CVA6-associated pathology in vivo, and treatment with IL-6 accelerated the death of neonatal mice. Both specific anti-CVA6 serum and maternal antibody play important roles in controlling CVA6 infection and viral replication. Collectively, these findings indicate that this neonatal murine model will be invaluable in future studies to develop CVA6-specific antivirals and vaccines.IMPORTANCE Although coxsackievirus A6 (CVA6) infections are commonly mild and self-limiting, a small proportion of children may have serious complications, such as encephalitis, acute flaccid paralysis, and neurorespiratory syndrome, leading to fatalities. We have established a mouse model of CVA6 infection by inoculation of neonatal mice with a CVA6 clinical isolate that produced consistent pathological outcomes. Here, using this model of CVA6 infection, we found that high levels of IL-6 were associated with severe viral pneumonia and encephalitis, as in an evaluation of antiviral efficacy in vivo, IL-6 had no protective effect and instead accelerated death in neonatal mice. We demonstrated that, as antiviral drugs, both gamma interferon and ribavirin played important protective roles in the early stages of infection, with increased survival in treated neonatal mice challenged with CVA6. Moreover, active and passive immunization with the inactivated vaccines and anti-CVA6 serum also protected mice against homologous challenge infections.

Epidemics and aetiology of hand, foot and mouth disease in Xiamen, China, from 2008 to 2015

Over the past 8 years, human enteroviruses (HEVs) have caused 27 227 cases of hand, foot and mouth disease (HFMD) in Xiamen, including 99 severe cases and six deaths. We aimed to explore the molecular epidemiology of HFMD in Xiamen to inform the development of diagnostic assays, vaccines and other interventions. From January 2009 to September 2015, 5866 samples from sentinel hospitals were tested using nested reverse transcription PCR that targeted the HEV 5' untranslated region and viral protein 1 region. Of these samples, 4290 were tested positive for HEV and the amplicons were sequenced and genotyped. Twenty-two genotypes were identified. Enterovirus 71 (EV71) and coxsackieviruses A16, A6 and A10 (CA16, CA6 and CA10) were the most common genotypes, and there were no changes in the predominant lineages of these genotypes. EV71 became the most predominant genotype every 2 years. From 2013, CA6 replaced CA16 as one of the two most common genotypes. The results demonstrate the vast diversity of HFMD pathogens, and that minor genotypes are able to replace major genotypes. We recommend carrying-out long-term monitoring of the full spectrum of HFMD pathogens, which could facilitate epidemic prediction and the development of diagnostic assays and vaccines.

A Case-control Study on Risk Factors for Severe Hand, Foot and Mouth Disease

The objective of this study was to identify potential risk factors for severe hand, foot and mouth disease (HFMD). In this case-control study, 459 severe HFMD patients and 246 mild HFMD patients from Guangdong province and Henan province, China were included. Data comprising demographic characteristics, clinical symptoms and signs, laboratory findings and other factors were collected. Univariate analysis revealed 30 factors associated with severe cases. Further multivariate analysis indicated four independent risk factors: fatigue (p < 0.01, odd ratio [OR] = 204.7), the use of glucocorticoids (p = 0.03, OR = 10.44), the use of dehydrant drugs (p < 0.01, OR = 73.7) and maculopapular rash (p < 0.01, OR = 84.4); and one independent protective factor: herpes or ulcers in mouth (p = 0.01, OR = 0.02). However, more systematic research and validation are needed to understand the underlying risk factors for severe HFMD.

Hand, Foot, and Mouth Disease in Hunan Province, China, 2009-2014: Epidemiology and Death Risk Factors

Hand, foot, and mouth disease (HFMD) is an arising public health problem in Asia, including China. Epidemiological data is necessary to enable judicious public health responses and interventions. We analyzed the epidemiological and laboratory data of 759,301 HFMD cases reported to the Hunan Provincial Center for Disease Control and Prevention from 1 January 2009 to 31 December 2014. Univariate and multivariable conditional logistic regression analyses were used to identify risk factors of fatality in HFMD. The incidence of HFMD was highest among children aged 1-3 years, compared with other age groups. Of the total HFMD cases, 7,222 (0.95%) were considered severe and 338 (0.04%) were fatal. Enterovirus-A71 was the major cause of severe and fatal cases (65.75% and 88.78%, respectively). For severe cases, the median time from symptom onset to diagnosis was 0.5 days (interquartile range [IQR] 0-1.5 days); the median time from diagnosis to severe illness was 2 days (IQR 1-3 days). For fatal cases, the median time from symptom onset to diagnosis was 0.5 days (IQR 0-1.5 days); the median time from diagnosis to death was 1.5 days (IQR 0.5-2.5 days). In multivariable analysis, the abuse of antibiotic, glucocorticoid and pyrazolone in village clinics at basic medical institutions were identified as independent risk factors for HFMD fatal cases. In conclusion, our results suggest that the future direction to control and respond to HFMD is intensive surveillance of enterovirus-A71 and improving the ability to diagnose disease and treat patients, especially in basic medical institutions.

Glucocorticoids Prevent Enterovirus 71 Capsid Protein VP1 Induced Calreticulin Surface Exposure by Alleviating Neuronal ER Stress

Severe hand-foot-and-mouth disease (HFMD) caused by Enterovirus 71 (EV71) always accompanies with inflammation and neuronal damage in the central nervous system (CNS). During neuronal injuries, cell surface-exposed calreticulin (Ecto-CRT) is an important mediator for primary phagocytosis of viable neurons by microglia. Our data confirmed that brainstem neurons underwent neuronophagia by glia in EV71-induced death cases of HFMD. EV71 capsid proteins VP1, VP2, VP3, or VP4 did not induce apoptosis of brainstem neurons. Interestingly, we found VP1-activated endoplasmic reticulum (ER) stress and autophagy could promote Ecto-CRT upregulation, but ER stress or autophagy alone was not sufficient to induce CRT exposure. Furthermore, we demonstrated that VP1-induced autophagy activation was mediated by ER stress. Meaningfully, we found dexamethasone treatment could attenuate Ecto-CRT upregulation by alleviating VP1-induced ER stress. Altogether, these findings identify VP1-promoted Ecto-CRT upregulation as a novel mechanism of EV71-induced neuronal cell damage and highlight the potential of the use of glucocorticoids to treat severe HFMD patients with CNS complications.

An epidemic analysis of hand, foot, and mouth disease in Zunyi, China between 2012 and 2014

OBJECTIVES

To re-evaluate the epidemiology of hand, foot, and mouth disease (HFMD) in a non-vaccinated population in Zunyi, China.

METHODS

We used laboratory-based data from the Third Affiliated Hospital of Zunyi Medical College, Zunyi, China to assess the epidemiology of the HFMD caused by enteroviruses between January 2012 and November 2014. Real-time polymerase chain reaction was used to determine human enteroviruses from a total of 12313 probable cases enrolled in this retrospective study. All analyses were stratified by enterovirus serotype, gender, and age.

RESULTS

Virological results were available for 12313 cases of probable HFMD. A total of 5750 cases were positive for viral detection, and the positive rates of infection caused by other enteroviruses was 46.7%, EV71 9%, and CVA16 4.7%. During the study period there was a substantial increase in the occurrence of HFMD. Most of the HFMD patients (87.4%) were aged 0-59 months (median 24; range 0-59). Males showed a higher HFMD prevalence rate (62.4%) than females (37.6%).

CONCLUSION

Enterovirus infection remains an important public health problem and other entroviruses are emerging as the major causative agent of the HFMD in Zunyi, China.

Children's Caregivers and Public Playgrounds: Potential Reservoirs of Infection of Hand-foot-and-mouth Disease

Hand-foot-and-mouth disease (HFMD) is a common infectious disease, which has led to millions of clinical cases and hundreds of deaths every year in China. This study aimed to exploring the effects on HFMD transmission of children’s caregivers and public area, as well as trying to locate the potential reservoirs of infections in primary cases. Total children’s 257 samples (98 children’s caregivers and 159 environmental samples) were tested for the presence of universal enterovirus, enterovirus 71, coxsackie virus A6 and A16 by real-time fluorescence quantitative polymerase chain reaction (qPCR). 5.84% (15/257, 95% confidence interval [CI]: 2.98%, 8.70%) of total samples had positive results of enterovirus. The enterovirus positive rates of children’s caregiver samples and environmental samples were respectively 7.14% (7/98, 95% CI: 2.04%, 12.24%), and 5.03% (8/159, 95% CI: 1.63%, 8.43%); 7.61% (7/92, 95% CI: 2.21%, 13.01%) of wiping samples from playgrounds and 1.49% (1/67, 95% CI: 0, 7.00%) of air samples in indoor market places had positive result of enterovirus. High positive rates of enterovirus in children’s caregivers and from playgrounds indicated that they would be potential reservoirs of HFMD infection, as children might be infected via contacting with asymptomatic-infected individuals or exposure of contaminated surface of public facilities.

Large outbreak of herpangina in children caused by enterovirus in summer of 2015 in Hangzhou, China

Herpangina, usually caused by coxsackie virus A, is prevalent in children spreading through the fecal-oral transmission and the respiratory droplets dissemination. Also, it is mostly asymptomatic and self-limiting. In our study, we found that large outbreak of herpangina in children occurred in the summer of 2015 in Hangzhou, China. From May 1th to August 31th, a total of 10 210 children were diagnosed with herpangina in Children’s Hospital of Zhejiang University School of Medicine. 2 310 throat swabs were collected and tested for enterovirus detection by real-time RT-PCR, while 1 651 cases were positive with the rate of 71.5%. Based on VP1 gene or 5′UTR region sequences, Coxsackievirus A2, A4, A6, A10, B2, B4 and echovirus 30 were detected in these cases. More importantly, Coxsackievirus A2 may be the major subtype of enterovirus resulting in children with herpangina in hangzhou, China.

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.

Development and evaluation of a rapid recombinase polymerase amplification assay for detection of coxsackievirus A6

Coxsackievirus A6 (CV-A6) is an important pathogen causing hand, foot and mouth disease (HFMD). The aim of this study was to develop and evaluate a rapid real-time reverse transcription recombinase polymerase amplification (RT-RPA) assay for detection of CV-A6. The sensitivity of this assay was 202 copies/reaction, with 100 % specificity. Furthermore, this assay yielded consistent results comparable with a commercial qRT-PCR diagnostic kit. This assay is therefore potentially useful for surveillance of CV-A6 infections and outbreak control.

Epidemiological and genetic analysis of hand-foot-mouth disease by enterovirus A71 in Taizhou, P. R. China, between 2010 and 2013

Out of a population of 1,098 enteroviruses (EVs)-positive hand, foot, and mouth disease (HFMD) specimens, 352 were screened positive for EV-A71-accounting for 32.1% of all EV-positive specimens. This percentage denotes EV-A71 as the second major serotype of enteroviruse among HFMD suffers in Taizhou. An epidemic outbreak of EV-A71 among HFMD children was found in Taizhou in the second quarter of 2012. Phylogeny analysis based on the VP1 complete sequences leads us to find a sub-clade (designated TZ1-1) of EV-A71 circulating in Taizhou, whose emergence might be correlated with the epidemic outbreak. This correlation was further supported by the followed two analyses (namely skyline plot of population history and birth-death SIR simulation of epidemic history). And more importantly, at a positively selected site of VP1 caspid, a mutation of N31D was found to be a synapomorphy of TZ1-1 and its occurrence might be correlated with the epidemic outbreak. J. Med. Virol. 89:782-790, 2017. © 2016 Wiley Periodicals, Inc.

Outbreak of hand, foot, and mouth disease caused by coxsackievirus A6 in a Juku in Fengtai District, Beijing, China, 2015

An outbreak of hand, foot, and mouth disease (HFMD) that occurred in a Juku in Fengtai District, Beijing, China, in 2015 was monitored by the China Information System for Disease Control and Prevention. Epidemiological investigation showed that 11 cases occurred from two classes in the preschool art training department in the Juku. Coxsackievirus A6 (CV-A6) was identified as the causative pathogen of the outbreak via sequences analysis of products of real-time reverse-transcription polymerase chain reaction (RT-PCR) and nested RT-PCR. Phylogenetic analysis showed that CV-A6 strains isolated in this study clustered with epidemic strains isolated in China since 2013. The outbreak ended quickly with effective measures. This event indicates that continuous surveillance of HFMD etiological agents other than enterovirus 71 and coxsackievirus A16 is necessary.

Changes in enterovirus serotype constituent ratios altered the clinical features of infected children in Guangdong Province, China, from 2010 to 2013

Background

Enterovirus (EV)-related hand, foot, and mouth disease/herpangina (HFMD/HA) has been prevalent in Guangdong Province, China, since 2010.

Methods

Clinical data for EV-related HFMD/HA inpatients admitted to the Department of Paediatrics of Zhujiang Hospital from 2010 to 2013 were retrospectively reviewed. The corresponding EV serotypes were also determined by reverse transcription-polymerase chain reaction or BLAST analysis of the sequenced partial lengths of the viral protein1/5′-untranslated region.

Results

A total of 867 eligible inpatients admitted during 2010–2013 were included in the study. Of these, the serotype of the responsible EV was successfully identified in 824 cases. The incidence of enterovirus 71 (EV71) infection amongst pediatric HFMD/HA inpatients decreased dramatically from 55.5 % in 2010 to 8.1 % in 2013, with a similar decrease recorded for coxsackievirus A16 (CVA16). However, the incidence of non-EV71/CVA16 infection increased from 30.0 % in 2010 to 83.8 % in 2013. We noted that the types of infection caused by different EV serotypes varied: EV71 was responsible for 100 % of the paralysis cases (26/26), 84.6 % of the deaths (11/13), and 84.1 % of cases with severe central nervous system involvement (SCNSI) (74/88); echovirus contributed to 16.4 % of the deaths (2/13) and 4.4 % of the SCNSI cases; and coxsackievirus accounted for only 2.2 % of the SCNSI cases (2/90). The clinical features of HFMD/HA cases varied greatly during the time period examined, with drastic changes in the hospitalization rates (45.1, 63.7, 36.4, and 19.1 % for 2010, 2011, 2012, and 21013, respectively), mortality rates (2.3, 0.9, 2.5, and 0.0 %, respectively), paralysis (5.1, 1.2, 5.4, and 0.0 %, respectively), SCNSI (16.8, 7.1, 12.7, and 2.2 %, respectively), and acute respiratory infection (21.1, 22.0, 45.9, and 59.0 %, respectively).

Conclusions

The incidences of infection caused by different EV serotypes, along with the clinical features of HFMD/HA cases, changed drastically in Guangdong Province, China, from 2010 to 2013, with the biggest changes observed in 2013. The changed constituent ratios of the different EV serotypes might therefore be responsible for the differences in the observed clinical features of HFMD/HA during this period.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1690-0) contains supplementary material, which is available to authorized users.

Characterization of VP1 sequence of Coxsackievirus A16 isolates by Bayesian evolutionary method

BACKGROUND

Coxsackievirus A16 (CV-A16), a major etiopathologic cause of pediatric hand, foot, and mouth disease (HFMD) worldwide, has been reported to have caused several fatalities. Revealing the evolutionary and epidemiologic dynamics of CV-A16 across time and space is central to understanding its outbreak potential.

METHODS

In this study, we isolated six CV-A16 strains in China's Jilin province and construct a maximum clade credibility (MCC) tree for CV-A16 VP1 gene by the Bayesian Markov Chain Monte Carlo method using 708 strains from GenBank with epidemiological information. The evolution characteristics of CV-A16 VP1 gene was also analysed dynamicly through Bayesian skyline plot.

RESULTS

All CV-A16 strains identified could be classified into five major genogroups, denoted by GI-GV. GIV and GV have co-circulated in China since 2007, and the CV-A16 epidemic strain isolated in the Jilin province, China, can be classified as GIV-3. The CV-A16 genogroups circulating recently in China have the same ancestor since 2007. The genetic diversity of the CV-A16 VP1 gene shows a continuous increase since the mid-1990s, with sharp increases in genetic diversity in 1997 and 2007 and reached peak in 2007. Very low genetic diversity existed after 2010. The CV-A16 VP1 gene evolutionary rate was 6.656E-3 substitutions per site per year.

CONCLUSIONS

We predicted the dynamic phylogenetic trends, which indicate outbreak trends of CV-A16, and provide theoretical foundations for clinical prevention and treatment of HFMD which caused by a CV-A16.

Development and evaluation of a non-ribosomal random PCR and next-generation sequencing based assay for detection and sequencing of hand, foot and mouth disease pathogens

Background

Hand, foot and mouth disease (HFMD) has become a major public health problem across the Asia-Pacific region, and is commonly caused by enterovirus A71 (EV-A71) and coxsackievirus A6 (CV-A6), CV-A10 and CV-A16. Generating pathogen whole-genome sequences is essential for understanding their evolutionary biology. The frequent replacements among EV serotypes and a limited numbers of available whole-genome sequences hinder the development of overlapping PCRs for whole-genome sequencing.

We developed and evaluated a non-ribosomal random PCR (rPCR) and next-generation sequencing based assay for sequence-independent whole-genome amplification and sequencing of HFMD pathogens. A total of 16 EV-A71/CV-A6/CV-A10/CV-A16 PCR positive rectal/throat swabs (Cp values: 20.9–33.3) were used for assay evaluation.

Results

Our assay evidently outperformed the conventional rPCR in terms of the total number of EV-A71 reads and the percentage of EV-A71 reads: 2.6 % (1275/50,000 reads) vs. 0.1 % (31/50,000) and 6 % (3008/50,000) vs. 0.9 % (433/50,000) for two samples with Cp values of 30 and 26, respectively. Additionally the assay could generate genome sequences with the percentages of coverage of 94–100 % of 4 different enterovirus serotypes in 73 % of the tested samples, representing the first whole-genome sequences of CV-A6/10/16 from Vietnam, and could assign correctly serotyping results in 100 % of 24 tested specimens. In all but three the obtained consensuses of two replicates from the same sample were 100 % identical, suggesting that our assay is highly reproducible.

Conclusions

In conclusion, we have successfully developed a non-ribosomal rPCR and next-generation sequencing based assay for sensitive detection and direct whole-genome sequencing of HFMD pathogens from clinical samples.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0580-9) contains supplementary material, which is available to authorized users.

Hand-Washing: The Main Strategy for Avoiding Hand, Foot and Mouth Disease

Epidemics of hand, foot and mouth disease (HFMD) among children have caused concern in China since 2007. We have conducted a retrospective study to investigate risk factors associated with HFMD. In this non-matching case-control study, 99 HFMD patients and 126 control from Guangdong Province were enlisted as participants. Data comprising demographic, socio-economic, clinical and behavior factors were collected from children's parents through face-to-face interviews by trained interviewers using a standardized questionnaire. Results of the primary logistic regression analyses revealed that age, history of cold food consumption, hand-washing routines, and airing out bedding were significantly associated with HFMD cases. Results of further multivariate analysis indicated that older age (OR = 0.44, 95% CI: 0.34-0.56) and hand-washing before meals (OR = 0.3, 95% CI: 0.13-0.70) are protective factors, whereas airing out bedding more than thrice a month (OR = 4.55, 95% CI: 1.19-17.37) was associated with increased risk for HFMD. Therefore, hand-washing should be recommended to prevent HFMD, and the potential threat of airing out bedding should be carefully considered. However, further studies are needed to examine other possible risk factors.

Yeast-produced recombinant virus-like particles of coxsackievirus A6 elicited protective antibodies in mice

Coxsackievirus A6 (CA6) has recently emerged as the predominant pathogen of hand, foot and mouth disease (HFMD), causing significant morbidity in children and adults. The increasing prevalence of CA6 infection and its associated disease burden underscore the need for effective CA6 vaccines. However, CA6 grows poorly in cultured cells, making it difficult to develop inactivated whole-virus or live attenuated vaccines. Here we report the development of a recombinant virus-like particle (VLP) based CA6 vaccine. CA6 VLPs were produced in Pichia pastoris yeast transformed with a vector encoding both P1 and 3CD proteins of CA6. Immunization with CA6 VLPs elicited CA6-specific serum antibodies in mice. Passive transfer of anti-VLP antisera protected recipient mice against lethal CA6 challenge. Collectively, these results demonstrate that CA6 VLPs represent a viable CA6 vaccine candidate which warrants further preclinical and clinical development.

Detecting spatial-temporal cluster of hand foot and mouth disease in Beijing, China, 2009-2014

Background

The incidence of hand, foot, and mouth disease (HFMD) is extremely high, and has constituted a huge disease burden throughout Beijing in recent years. This study aimed to determine the spatiotemporal distribution and epidemic characteristics of HFMD.

Methods

Descriptive statistics was used to analyze the data and estimate the epidemic peaks in 2009–2014. Space–time scanning detected spatiotemporal clusters and identified high-risk locations. Global and local Moran’s I statistics were used to measure the spatial autocorrelation. Geocoding was performed in ArcGIS, based on the present address codes of the patients and the centroids of the towns. Maps were created in ArcGIS to show the geographic spread of HFMD.

Results

In total, 220,451probable cases of HFMD were reported in Beijing between January 2009 and December 2014: 12,749 (5.78 %) were laboratory confirmed, and 35 (0.02 %) were fatal. The median age of reported cases was 3.12 years (interquartile range 1.96–4.39). Coxsackievirus A16 (CV-A16), enterovirus 71 (EV-A71), and other enteroviruses accounted for 39.31, 35.36, and 25.33 % of the 12,749 confirmed cases, respectively. Many more severe cases were caused by EV-A71 (χ² = 186.41, df = 1, P < 0.001) and other enteroviruses (χ² = 156.44, df = 1, P < 0.001) than by CV-A16. A large single distinct peak occurred between May and July each year. Spatiotemporal clusters of HFMD were identified in Beijing during 2009–2014. The most likely clusters were detected and tended to move from the southwest (Fengtai and Daxing) southeastwards to Daxing and Tongzhou in 2009–2014. The incidence of HFMD was not randomly distributed, but showed global and local spatial autocorrelations.

Conclusions

There were obvious spatiotemporal clusters of HFMD in Beijing in 2009–2014. High-incidence areas mainly occurred at the junctions of urban and rural zones. More attention should be paid to the epidemiological and spatiotemporal characteristics of HFMD to establish new strategies for its control. Health issues should be especially promoted in kindergartens and at urban–rural junctions.