Genotypes of the Enterovirus Causing Hand Foot and Mouth Disease in Shanghai, China, 2012-2013

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.

Effects of temperature and PM2.5 on the incidence of hand, foot, and mouth in a heavily polluted area, Shijiazhuang, China

The influence of weather and air pollution factors on hand, foot, and mouth disease (HFMD) has received widespread attention. However, most of the existing studies came from lightly polluted areas and the results were inconsistent. There was a lack of relevant evidence of heavily polluted areas. This study aims to quantify the relationship between weather factors and air pollution with HFMD in heavily polluted areas. We collected the daily number of hand, foot, and mouth disease in Shijiazhuang, China from 2014 to 2018, as well as meteorological and air pollutant data over the same period. The generalized linear model combined with the distributed lag model was used to study the effect of meteorological factors and air pollutants on the daily cases of HFMD and its hysteresis effect. We found that the dose-response relationship between temperature, PM_2.5, and the risk of hand-foot-mouth disease was non-linear. Both low temperature and high temperature increased the risk of hand-foot-mouth disease. The cumulative effect of high temperature reached the maximum at 0-10 lag days, and the cumulative effect of low temperature reached the maximum at 0-3 lag days. The concentration of PM_2.5 between 76 and 200 μg/m³ has a certain risk of the onset of hand, foot, and mouth disease, but the extreme PM_2.5 concentration has a certain protective effect. In addition, low humidity, low wind speed, and low-O₃ can increase the risk of HFMD. Risks of humidity and low concentration of O₃ increased as lag days extended. In conclusion, our study found that climate factors and air pollutants exert varying degrees of impact on HFMD. Our research provided the scientific basis for establishing an early warning system so that medical staff and parents can take corresponding measures to prevent HFMD.

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.

A five-year retrospective study on the epidemiology of hand, foot and mouth disease in Sabah, Malaysia

Hand, foot, and mouth disease (HFMD) is endemic in Malaysia, with the number of cases increasing. Sabah has experienced several HFMD outbreaks, but information on the epidemiology and molecular characteristics of responsible viruses is scarce. In this study, data of 17,574 reports of HFMD cases in Sabah from 2015 to 2019 were extracted from a public health disease surveillance system and analyzed. Twenty-one swab samples from 13 children were collected from Beaufort, Sabah, during an outbreak in August 2018 for detection and serotyping of causative viruses by semi-nested reverse transcription-polymerase chain reaction (snRT-PCR) of the VP4–VP2 region and consensus degenerate hybrid oligonucleotide primer PCR of the VP1 region, respectively. Nucleotide sequencing and phylogenetic analysis were conducted by the neighbor-joining method. The average annual incidence of HFMD was 94.3 per 100,000 people, with the greatest yearly increase between 2017 and 2018. Swabs from six children were tested positive for enterovirus, of which five were positive for CVA16 and one for EV71. All CVA16 strains belonged to sub-genotype B1a, and the EV71 strain belonged to sub-genotype B5. Phylogenetic analyses indicate that enterovirus genotype shift might be responsible for the increasing trend of HFMD in Sabah, however, further study is needed.

Pathogenic characteristics of hand, foot and mouth disease in Shaanxi Province, China, 2010-2016

Hand, foot, and mouth disease (HFMD) is a common childhood illness caused by enteroviruses. We analyzed the pathogenic characteristics of HFMD in Shaanxi province, China, during 2010-2016. Clinical samples were collected from HFMD cases. Real-time PCR and RT-PCR were used to identify the enterovirus(EVs) serotypes. Viral RNA sequences were amplified using RT-PCR and compared by phylogenetic analysis. Descriptive epidemiological methods were used to analyze. A total of 16,832 HFMD positive cases were confirmed in the laboratory. EV-A71 and CV-A16 were the main pathogens in 2010. EV-A71 was the dominant pathogen in the periods of 2011 to 2012 and 2014, 2016. In 2013 and 2015, other EVs increased greatly, in which CV-A6 was the predominant pathogen. EV-A71 was more frequently detected in deaths and severe cases. Phylogenetic analysis revealed that EV-A71 belonged to the C4a evolution branch of C4 sub-genotype and CV-A16 belonged to the B1a or B1b evolution branch of B1 sub-genotype, whereas CV-A6 strains were assigned to D2 or D3 sub-genotype. The pathogen spectrum of HFMD has changed in 7 years, and the major serotypes EV-A71, CV- A16 and CV- A6 alternated or co-circulated. Long-term surveillance and research of EVs should be strengthened for the prevention and control of HFMD.

Newly emerged enterovirus-A71 C4 sublineage may be more virulent than B5 in the 2015-2016 hand-foot-and-mouth disease outbreak in northern Vietnam

Enterovirus-A71 (EV-A71) is a common cause of hand-foot-and-mouth disease (HFMD) and, rarely, causes severe neurological disease. This study aimed to elucidate the epidemiological and genetic characteristics and virulence of EV-A71 strains isolated from children diagnosed with HFMD. Rectal and throat swabs were collected from 488 children with HFMD in Hanoi, Vietnam, in 2015-2016. From 391 EV-positive patients, 15 EVs, including coxsackievirus A6 (CV-A6; 47.1%) and EV-A71 (32.5%, n = 127), were identified. Of the 127 EV-A71 strains, 117 (92.1%) were the B5 subgenotype and 10 (7.9%) were the C4 subgenotype. A whole-genome analysis of EV-A71 strains showed that seven of the eight C4a strains isolated in 2016 formed a new lineage, including two possible recombinants between EV-A71 C4 and CV-A8. The proportion of inpatients among C4-infected children was higher than among B5-infected children (80.0% vs. 27.4%; P = 0.002). The virulence of EV-A71 strains was examined in human scavenger receptor class B2 (hSCARB2)-transgenic mice, and EV-A71 C4 strains exhibited higher mortality than B5 strains (80.0% vs. 30.0%, P = 0.0001). Thus, a new EV-A71 C4a-lineage, including two possible recombinants between EV-A71 C4 and CV-A8, appeared in 2016 in Vietnam. The EV-A71 C4 subgenotype may be more virulent than the B5 subgenotype.

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.

Impacts of tropical cyclones and accompanying precipitation and wind velocity on childhood hand, foot and mouth disease in Guangdong Province, China

OBJECTIVE

Guangdong province is one of the provinces most frequently hit by tropical cyclones in China. Hand, foot and mouth disease (HFMD) continues to severely affect public health across the world. Our study aimed to evaluate the impacts of different grades of tropical cyclones and accompanying precipitation and wind velocity on HFMD among children younger than 6 years old in Guangdong province from 2009 to 2013.

METHODS

A time-stratified case-crossover design was used to examine the association between tropical cyclones and childhood HFMD. Principal component analysis (PCA) was first used to eliminate multicollinearity among meteorological variables. Conditional Poisson regression was then applied to calculate odds ratios (ORs) and the 95% confidence intervals (CIs).

RESULTS

Tropical storms increased the risk of HFMD among children below 6 years of age on lag 4 days (OR = 1.55, 95%CI: 1.28-1.88). Tropical storms were also a risk factor for boys below 3 years of age, boys between 3 and 6 and girls below 3 years of age with the largest OR = 1.52 (95%CI:1.15-2.00), OR = 1.81 (95%CI = 1.21-2.71) and OR = 1.51 (95%CI = 1.04-2.19), respectively. Precipitation during tropical cyclones had an adverse effect on childhood HFMD when reaching 25-49.9 mm or above 100 mm with OR = 1.20 (95%CI = 1.00-1.43) on lag 0 day and OR = 1.25 (95%CI = 1.04-1.49) on lag 7 days, respectively. For extreme wind velocity during tropical cyclones, the impact on childhood HFMD was largest on the day tropical cyclones landed (OR = 1.25, 95%CI: 1.06-1.48) with winds up to 13.9-24.4  m/s.

CONCLUSIONS

Tropical storms can increase the risk of HFMD among children younger than 3 years old, especially boys between 3 and 6 years old. Precipitation during tropical cyclones is a risk factor for childhood HFMD when it is between 25 and 49.9 mm or above 100 mm. As extreme wind velocity reaches 13.9-24.4  m/s, it has an adverse effect on children's health. Children below 3 years old and boys between 3 and 6 should be given more consideration during tropical storms.

A Bacillus-based Coxsackie virus A16 mucosal vaccine induces strong neutralizing antibody responses

The purpose of this study was to construct a Coxsackie virus A16 (CA16) mucosal vaccine and evaluate its ability to induce immune response. VP1 gene of CA16 was inserted into the genome of Bacillus subtilis via recombination and displayed on the surface of the spores. This Bacillus-based vaccine was used for intranasal immunization of mice and the serum antibody titer was determined by enzyme-linked immunosorbent assay (ELISA). Neutralization activity of the serum from immunized mice was analyzed by an in vitro neutralizing test. VP1 gene was successfully integrated into the genome of Bacillus subtilis and was expressed on the surface of Bacillus spores. Intranasal immunization of mice with this vaccine induced a higher level of VP1 specific IgA and IgG than in mice of the control group (p < 0.05). The neutralizing antibody titer in the spore immunization group was 1 : 169, which was higher than that in the control group (p < 0.05). We concluded that vaccine prepared by displaying CA16 VP1 protein on the surface of Bacillus subtilis spores can stimulate mice to produce protective neutralizing antibodies, which provides foundations for the development of CA16 mucosal vaccine.

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.

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.

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.

An Environmental Surveillance in Uruguay Reveals the Presence of Highly Divergent Types of Human Enterovirus Species C and a High Frequency of Species A and B Types

Information about Human Enterovirus circulation in Uruguay is scarce. The aim of this study was to generate the first description about their circulation in the country through the study of sewage samples collected before and after the switch from Oral Poliovirus Vaccine to Inactivated Poliovirus Vaccine. Viruses were concentrated by an adsorption-elution to a negatively charged membrane, and real-time quantitative PCR and qualitative PCR methods were used to detect, quantify, and characterize enteroviruses. Positive samples were inoculated in RD cells and two passages were performed. Additionally, RD+ samples were subsequently passed onto L20B cells. Human Enteroviruses were detected in 67.6% of the samples, with concentrations between 4.9 and 6.6 Log₁₀ genomic copies per liter. 10% of positive samples replicated in RD cells, of which none in L20B cells. Molecular characterization of Human Enterovirus strains directly detected from sewage sample concentrates allowed the identification of highly divergent members of species C such as Enterovirus C99 and Coxsackievirus A13, as well as the frequent detection of species A and B members (particularly Coxsackievirus A16 and Echovirus 6, respectively). Other detected types were Coxsackievirus A2, A22, B1, B5, Echovirus 5, and 9. The characterization of viruses isolated in cell culture revealed the presence of Echovirus 6 and Coxsackievirus B3. Despite the absence of poliovirus, a wide circulation of different enterovirus types was evidenced in Uruguayan sewage samples, highlighting that the local populations are exposed to different kinds of diseases originated by several human enterovirus.

Temporal relationship between occurrences of hand, foot and mouth disease, respiratory virus detection and febrile seizures in children in tropical Singapore: a time-series analysis

Febrile seizure (FS) in children is a common complication of infections with respiratory viruses and hand, foot and mouth disease (HFMD). We conducted a retrospective ecological time-series analysis to determine the temporal relationship between hospital attendances for FS and HFMD or respiratory virus infections. Epilepsy attendance was used as a control. Data from 2004 to 2012 FS and epilepsy hospital attendance, HFMD notifications to the Ministry of Health and from laboratory-confirmed viral respiratory infections among KK Women's and Children's Hospital inpatients were used. A multivariate linear regression analysis was conducted to evaluate the relationship between FS and the virus time series. Relative risks of FS by age were calculated using Bayesian statistical methods. Paediatric accident and emergency (A&E) attendances for FS were found to be associated with influenza A (extra 0.47 FS per influenza A case), B (extra 0.32 per influenza B case) and parainfluenza 3 (extra 0.35 per parainfluenza type 3 case). However, other viruses were not significantly associated with FS. None of the viruses were associated with epileptic seizure attendance. Influenza A, B and parainfluenza 3 viruses contributed to the burden of FS resulting in A&E attendance. Children at risk of FS should be advised to receive seasonal influenza vaccination.

Recent development of enterovirus A vaccine candidates for the prevention of hand, foot, and mouth disease

INTRODUCTION

Hand, foot, and mouth disease (HFMD) is a childhood illness commonly caused by enterovirus A. Enterovirus A71 (EV-A71) and coxsackievirus A16 (CV-A16) are the most commonly identified viruses associated with HFMD. Recently, outbreaks caused by different enterovirus A including CV-A6 and CV-A10 are increasing. Being available now to protect against EV-A71 infection, inactivated EV-A71 vaccines cannot prevent coxsackievirus infections, thus limiting their general application in controlling HFMD. Multivalent HFMD vaccines are suggested to have broad cross-neutralizing responses against these emerging enteroviruses.

AREAS COVERED

We discuss the recent development of enterovirus A vaccines including the inactivated whole-virion vaccine and virus-like particle vaccine candidates and review the information of neutralization epitopes of these viruses.

EXPERT COMMENTARY

Evaluation of the efficacy and safety of the coxsackievirus vaccine and the multivalent HFMD vaccine candidates in clinical trials is urgently required. Epitopic analysis showed that common immunodominant sites exist across these enteroviruses. However, variations of amino acid residues in these regions limit the induction of cross-neutralization antibodies, and therefore, a multivalent HFMD vaccine is required for broad protection against HFMD. With the inclusion of major circulating viruses in the development of multivalent HFMD vaccines, an increase in the success in HFMD control is anticipated.

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.

The dynamics of the hand, foot and mouth disease epidemic from 2008 to 2016 in Zhenjiang city, China

AIM

To investigate the hand, foot and mouth disease (HFMD) epidemic in Zhenjiang, China from 2008 to 2016.

MATERIALS & METHODS

A total of 37,202 HFMD cases were investigated and 3707 nasopharyngeal swabs were detected for enterovirus RNA using RT-quantitative PCR.

RESULTS

We first reported a mixed pattern of HFMD seasonal epidemic with a combination of single-peak and two-peak patterns in alternate years, and the occurrence of sporadic and epidemic outbreaks of HFMD in kindergartens in Zhenjiang. Children younger than 4 years of age were highly vulnerable to HFMD, and home children and boys had higher risk to develop severe HFMD than nursery children and girls, respectively. Among tested samples, 1709 (46.1%) were detected as enterovirus RNA positive.

CONCLUSION

This study first presents the dynamic of the HFMD epidemic in Zhenjiang from 2008 to 2016.

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.

Hand, foot and mouth disease: current knowledge on clinical manifestations, epidemiology, aetiology and prevention

For a long time, hand, foot and mouth disease (HFMD) was seen as a mild viral infection characterized by typical clinical manifestations that spontaneously resolved in a few days without complications. In the past two decades, HFMD has received new attention because of evidence that this disease could have clinical, epidemiological and aetiological characteristics quite different from those initially thought. In contrast to previous beliefs, it has been clarified that HFMD can be associated with complications, leading to severe neurological sequelae and, rarely, to death. This finding has led to an enormous number of studies that have indicated that several viruses in addition to those known to be causes of HFMD could be associated with the development of disease. Moreover, it was found that if some viruses were more common in some geographic areas, frequent modification of the molecular epidemiology of the infecting strains could lead to outbreaks caused by infectious agents significantly different from those previously circulating. Vaccines able to confer protection against the most common aetiologic agents in a given country have been developed. However, simultaneous circulation of more than one causative virus and modification of the molecular epidemiology of infectious agents make preparations based on a single agent relatively inadequate. Vaccines with multiple components are a possible solution. However, several problems concerning their development must be solved before adequate prevention of severe cases of HFMD can be achieved.

Impact of meteorological factors on the incidence of childhood hand, foot, and mouth disease (HFMD) analyzed by DLNMs-based time series approach

BACKGROUND

Hand, foot, and mouth disease (HFMD) has become an emerging infectious disease in China in the last decade. There has been evidence that meteorological factors can influence the HFMD incidence, and understanding the mechanisms can help prevent and control HFMD.

METHODS

HFMD incidence data and meteorological data in Minhang District, Shanghai were obtained for the period between 2009 and 2015. Distributed lag non-linear models (DLNMs) were utilized to investigate the impact of meteorological factors on HFMD incidence after adjusting for potential confounders of long time trend, weekdays and holidays.

RESULTS

There was a non-linear relationship between temperature and HFMD incidence, the RR of 5th percentile compared to the median is 0.836 (95% CI: 0.671-1.042) and the RR of 95th percentile is 2.225 (95% CI: 1.774-2.792), and the effect of temperature varied across age groups. HFMD incidence increased with increasing average relative humidity (%) (RR = 1.009, 95% CI: 1.005-1.015) and wind speed (m/s) (RR = 1.197, 95% CI: 1.118-1.282), and with decreasing daily rainfall (mm) (RR = 0.992, 95% CI: 0.987-0.997) and sunshine hours (h) (RR = 0.966, 95% CI: 0.951-0.980).

CONCLUSIONS

There were significant relationships between meteorological factors and childhood HFMD incidence in Minhang District, Shanghai. This information can help local health agencies develop strategies for the control and prevention of HFMD under specific climatic conditions.

Epidemiological and serological surveillance of hand-foot-and-mouth disease in Shanghai, China, 2012-2016

Aside from enterovirus 71 (EV71) and coxsackie virus A16 (CV-A16), viruses that are known to cause hand-foot-and-mouth disease (HFMD), epidemiological profiles of other enteroviruses that induce HFMD are limited. We collected 9949 laboratory surveillance HFMD cases and 1230 serum samples from infants and children in Shanghai from 2012–2016. Since 2013, CV-A6 has displaced EV71 and CV-A16 to become the predominant serotype. Interestingly, novel epidemiological patterns in EV71 and CV-A16 infections were observed, with one large peak in both 2012 and 2014, followed by two smaller peaks in the respective following years (2013 and 2015). Through sequencing, we found that C4a, B1b, D-Cluster-1 and B constituted the major subgenotypes of EV71, CV-A16, CV-A6 and CV-A10, respectively. Among healthy individuals, 50.49% and 54.23% had positive neutralising antibodies (NtAbs) against EV71 and CV-A16, respectively, indicating that EV71 and CV-A16 silent infections were common. These populations may be an important potential source of infection. The overall seropositive rate of EV71 NtAbs showed a fluctuating, markedly downward trend, indicating the potential risk of a future EV71 epidemic. High CV-A16 NtAb seroprevalence corroborated a documented CV-A16 ‘silent’ epidemic. Children aged 1–5 years had the lowest EV71 NtAb seropositive rate, whereas those aged 1–2 years exhibited the lowest CV-A16 NtAb seropositive rate. This is the first comprehensive investigation of the epidemiology and aetiology, as well as the seroprevalence, of HFMD in Shanghai between 2012 and 2016. This study provides the latest insights into developing a more efficient HMFD vaccination programme.

A mutation-resistant deoxyribozyme OR gate for highly selective detection of viral nucleic acids

Highly selective probes hybridize only to fully complementary DNA or RNA sequences and, therefore, often fail to recognize mutated viral genomes. Here we designed a probe that possesses two seemingly incompatible properties: it tolerates some point mutations in genome, while it remains selective towards others. An OR deoxyribozyme logic gate was designed to fluorescently report the sequences of enterovirus 71 (EV71) covering ∼90% of all known EV71 strains. Importantly, sequences of closely related coxsackieviruses that differed by single nucleotides were reliably differentiated in 7 out of 8 cases.

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.

Platform technologies for modern vaccine manufacturing

Improved understanding of antigenic components and their interaction with the immune system, as supported by computational tools, permits a sophisticated approach to modern vaccine design. Vaccine platforms provide an effective tool by which strategically designed peptide and protein antigens are modularized to enhance their immunogenicity. These modular vaccine platforms can overcome issues faced by traditional vaccine manufacturing and have the potential to generate safe vaccines, rapidly and at a low cost. This review introduces two promising platforms based on virus-like particle and liposome, and discusses the methodologies and challenges.

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.

Molecular epidemiology of human enterovirus 71 at the origin of an epidemic of fatal hand, foot and mouth disease cases in Cambodia

Human enterovirus 71 (EV-A71) causes hand, foot and mouth disease (HFMD). EV-A71 circulates in many countries and has caused large epidemics, especially in the Asia-Pacific region, since 1997. In April 2012, an undiagnosed fatal disease with neurological involvement and respiratory distress occurred in young children admitted to the Kantha Bopha Children's Hospital in Phnom Penh, Cambodia. Most died within a day of hospital admission, causing public panic and international concern. In this study, we describe the enterovirus (EV) genotypes that were isolated during the outbreak in 2012 and the following year. From June 2012 to November 2013, 312 specimens were collected from hospitalized and ambulatory patients and tested by generic EV and specific EV-A71 reverse transcription PCR. EV-A71 was detected in 208 clinical specimens while other EVs were found in 32 patients. The VP1 gene and/or the complete genome were generated. Our phylogenetic sequencing analysis demonstrated that 80 EV-A71 strains belonged to the C4a subgenotype and 3 EV-A71 strains belonged to the B5 genotype. Furthermore, some lineages of EV-A71 were found to have appeared in Cambodia following separate introductions from neighboring countries. Nineteen EV A (CV-A6 and CV-A16), 9 EV B (EV-B83, CV-B3, CV-B2, CV-A9, E-31, E-2 and EV-B80) and 4 EV C (EV-C116, EV-C96, CV-A20 and Vaccine-related PV-3) strains were also detected. We found no molecular markers of disease severity. We report here that EV-A71 genotype C4 was the main etiological agent of a large outbreak of HFMD and particularly of severe forms associated with central nervous system infections. The role played by other EVs in the epidemic could not be clearly established.

Molecular identification of human enteroviruses associated with aseptic meningitis in Yunnan province, Southwest China

Human enteroviruses (EVs) are the major causative agents of aseptic meningitis. In this study, a total of 524 children were admitted to the children Kunming hospital (continental China) for aseptic meningitis manifestations in 2009 and 2010. An EV infection was diagnosed in 85/524 children (16.2 %) and the viruses detected were assigned to 16 serotypes. Most serotypes belonged to the enterovirus B species. Echovirus 9 was predominant (24.7 %), followed by coxsackievirus B5 (23.5 %) and then echovirus 30 (16.5 %). Echovirus 9 was firstly identified as the predominant serotype in sporadic aseptic meningitis which occurred in Yunnan, Southwest China. This work indicates the need to perform large-scale surveillance to gain a better insight into the epidemiology of enteroviruses associated with aseptic meningitis in China.

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.

Newly Identified Enterovirus C Genotypes, Identified in the Netherlands through Routine Sequencing of All Enteroviruses Detected in Clinical Materials from 2008 to 2015

Enteroviruses (EVs) are a group of human and animal viruses that are capable of causing a variety of clinical syndromes. Different genotypes classified into species can be distinguished on the basis of sequence divergence in the VP1 capsid-coding region. Apparently new genotypes are discovered regularly, often as incidental findings in studies investigating respiratory syndromes or as part of poliovirus surveillance. Recently, some EVs have become recognized as significant respiratory pathogens, and a number of new genotypes belonging to species C have been identified. The circulation of these newly identified species C EVs, such as EV-C104, EV-C105, EV-C109, and EV-C117, nevertheless appears to be limited. In this report, we show the results of routine genotyping of all enteroviruses detected in our tertiary care hospital between January 2008 and April 2015. We detected 365 EVs belonging to 40 genotypes. Interestingly, several newly identified species C EVs were detected during the study period. Sequencing of the 5′ untranslated region (5′ UTR) of these viruses shows divergence in this region, which is a target region in many detection assays.

Molecular epidemiology of human coxsackievirus A16 strains

The hand, foot and mouth disease (HFMD) epidemics have mainly been caused by human enterovirus 71 and human coxsackievirus A16 (CA16), which circulated alternatively or together in the epidemic area. The aim of the present study was to provide guidance in the prevention and control of HFMD from CA16 infection. The molecular epidemiology of the human CA16 strains was investigated. Overall, 1,151 specimens (throat swabs) were collected from 1,151 patients with HFMD symptoms. The results of the homology comparison in the VP1 of CA16 strains showed that the CA16 strains belonged to the B1b subgenotype. The difference of the 6 CA16 strains analyzed showed that the most prominent strain was the A genotype, and the most close strains were the B1 gene subtype, particularly the B1b gene subtype. With regards to the amino acids, in addition to the A genotype, the differences of amino acids with other gene subtype was not significant. The present data suggest that more effective and highly targeted intervention mechanisms could be developed for the prevention and control of HFMD.

Genetic evolution of Human Enterovirus A71 subgenotype C4 in Shenzhen, China, 1998-2013

BACKGROUND

Human Enterovirus A71 (EV-A71) is one of the severest enteroviruses that causes hand, foot, and mouth disease (HFMD) among children. This study identified the mutations of EV-A71 VP1 amino acid residues over a number of years and explored the possible association of identified mutations and HFMD epidemic outbreaks in Shenzhen, China.

METHODS

A total of 3760 stool specimens were collected from HFMD patients by Shenzhen Centers for Disease Control and Prevention (CDC) between 1998 and 2013. In total 289 VP1 strains were sequenced in this study, and amino acids mutation frequency was calculated. There were 2040 China nationwide sequences downloaded from Genebank as replication data.

RESULTS

In our samples, 1036 subjects (27.6%) were EV-A71 infected. Three amino acid positions on VP1 protein were found to have high mutation prevalence. These are Q22H, S283T, and A289H. Site 22 showed a fast mutation fixation in the year 2008, at the time of the large scale epidemic outbreak in Shenzhen. Analysis of the nationwide data replicated the same trend of mutation prevalence of the three sites.

CONCLUSION

The switching from Q to H on site 22 of the EV-A71 VP1 strain might be associated with the HFMD outbreak in Shenzhen in 2008. The identified amino acid sites 22, 283 and 289 provided information for developing anti-viral drugs against EV-A71 in the future.