Multirecombinant Enterovirus A71 Subgenogroup C1 Isolates Associated with Neurologic Disease, France, 2016-2017

Genetic diversity and spread of recombinant coxsackievirus A4 in hand, foot, and mouth disease cases in Bangkok, Thailand: 2017-2023

Coxsackievirus A4 (CVA4) has recently become one of the most common causative agents of hand, foot, and mouth disease. The current study investigated the genetic diversity and spread of recombinant CVA4 by analyzing circulating genotypes and recombinant strains in Bangkok, Thailand, from 2017 to 2023. Partial VP1, 3Dpol, and whole genome sequencing of CVA4 samples collected from collaborating hospitals were conducted. Phylogenetic analysis of CVA4 VP1 and 3Dpol genome regions revealed discordance, indicating recombination. The predominant CVA4 genotype was C3, primarily observed in 2019. The predominant genotype in 2017 was C1. D2, commonly found in China, was occasionally observed. In nucleotide similarity analysis, intertypic recombination between CVA4 and EV-A during the evolutionary history of the virus was evident, particularly in the nonstructural region. The estimated emergence of genotypes C1 and C3 in Thailand occurred around 2014, with an evolutionary rate of 5.8 × 10- 3 nucleotide substitutions per site per year. Genotype D2 exhibited notable variability across both the entire genome and the structural protein region compared to genotype C. Monitoring the genetic diversity and circulation of recombinant CVA4 is crucial for identifying newly emerging virus strains, enabling prompt public health responses and containment efforts, and enhancing surveillance in Thailand.

Molecular Genotyping of Circulating Enterovirus in the Lazio Region from 2012 to 2023

Enteroviruses (EVs) are ubiquitous viruses that circulate worldwide, causing sporadic or epidemic infections, typically during the summer and fall. They cause a broad spectrum of illnesses, ranging from an unspecified febrile clinical presentation to a severe illness. EVs are recognized to be the most frequent etiological agents of aseptic meningitis in children. However, as the infection is usually mild and self-limiting, it remains underestimated, and the epidemiology of EVs is poorly understood. To date, no vaccine or effective therapy for all types of enteroviruses is available, and EVs constitute a public health concern. Here, we investigated the molecular epidemiology of EV strains circulating in the Lazio region over a 10-year time span (2012-2023) by using a sequence-typing approach and phylogenetic analysis. The epidemiological trend of EV infection has undergone changes during the SARS-CoV-2 pandemic (2020-2021), which resulted in a modification in terms of the number of diagnosed cases and seasonality. From 2022, the circulation of EVs showed a behavior typical of the pre-pandemic period, although changes in predominantly circulating strains have been noted. Both epidemic and sporadic circulation events have been characterized in the Lazio region. Further analyses are needed to better characterize any strain with higher potential pathogenic power and to identify possible recombinant strains.

Enterovirus A71 crosses a human blood-brain barrier model through infected immune cells

Enterovirus A71 (EV-A71) is associated with neurological conditions such as acute meningitis and encephalitis. The virus is detected in the bloodstream, and high blood viral loads are associated with central nervous system (CNS) manifestations. We used an in vitro blood-brain barrier (BBB) model made up of human brain-like endothelial cells (hBLECs) and brain pericytes grown in transwell systems to investigate whether three genetically distinct EV-A71 strains (subgenogroups C1, C1-like, and C4) can cross the human BBB. EV-A71 poorly replicated in hBLECs, which released moderate amounts of infectious viruses from their luminal side and trace amounts of infectious viruses from their basolateral side. The barrier properties of hBLECs were not impaired by EV-A71 infection. We investigated the passage through hBLECs of EV-A71-infected white blood cells. EV-A71 strains efficiently replicated in immune cells, including monocytes, neutrophils, and NK/T cells. Attachment to hBLECs of immune cells infected with the C1-like virus was higher than attachment of cells infected with C1-06. EV-A71 infection did not impair the transmigration of immune cells through hBLECs. Overall, EV-A71 targets different white blood cell populations that have the potential to be used as a Trojan horse to cross hBLECs more efficiently than cell-free EV-A71 particles.IMPORTANCEEnterovirus A71 (EV-A71) was first reported in the USA, and numerous outbreaks have since occurred in Asia and Europe. EV-A71 re-emerged as a new multirecombinant strain in 2015 in Europe and is now widespread. The virus causes hand-foot-and-mouth disease in young children and is involved in nervous system infections. How the virus spreads to the nervous system is unclear. We investigated whether white blood cells could be infected by EV-A71 and transmit it across human endothelial cells mimicking the blood-brain barrier protecting the brain from adverse effects. We found that endothelial cells provide a strong roadblock to prevent the passage of free virus particles but allow the migration of infected immune cells, including monocytes, neutrophils, and NK/T cells. Our data are consistent with the potential role of immune cells in the pathogenesis of EV-A71 infections by spreading the virus in the blood and across the human blood-brain barrier.

Cost-effective complete genome sequencing using the MinION platform for identification of recombinant enteroviruses

IMPORTANCE

By employing a cost-effective approach for complete genome sequencing, the study has enabled the identification of novel enterovirus strains and shed light on the genetic exchange events during outbreaks. The success rate of genome sequencing and the scalability of the protocol demonstrate its practical utility for routine enterovirus surveillance. Moreover, the study's findings of recombinant strains of EVA71 and CVA2 contributing to epidemics in Malaysia and Taiwan emphasize the need for accurate detection and characterization of enteroviruses. The investigation of the whole genome and upstream ORF sequences has provided insights into the evolution and spread of enterovirus subgenogroups. These findings have important implications for the prevention, control, and surveillance of enteroviruses, ultimately contributing to the understanding and management of enterovirus-related illnesses.

Molecular Epidemiology of Enterovirus A71 in Surveillance of Acute Flaccid Paralysis Cases in Senegal, 2013-2020

Enterovirus A71 (EV-A71) is a non-polio enterovirus that currently represents a major public health concern worldwide. In Africa, only sporadic cases have been reported. Acute flaccid paralysis and environmental surveillance programs have been widely used as strategies for documenting the circulation of polio and non-polio enteroviruses. To date, little is known about the molecular epidemiology of enterovirus A71 in Africa where resources and diagnostic capacities are limited. To fill this gap in Senegal, a total of 521 non-polio enterovirus isolates collected from both acute flaccid paralysis (AFP) and environmental surveillance (ES) programs between 2013 and 2020 were screened for enterovirus A71 using real-time RT-PCR. Positive isolates were sequenced, and genomic data were analyzed using phylogeny. An overall rate of 1.72% (9/521) of the analyzed isolates tested positive for enterovirus A71. All positive isolates originated from the acute flaccid paralysis cases, and 44.4% (4/9) of them were isolated in 2016. The nine newly characterized sequences obtained in our study included eight complete polyprotein sequences and one partial sequence of the VP1 gene, all belonging to the C genogroup. Seven out of the eight complete polyprotein sequences belonged to the C2 subgenotype, while one of them grouped with previous sequences from the C1 subgenotype. The partial VP1 sequence belonged to the C1 subgenotype. Our data provide not only new insights into the recent molecular epidemiology of enterovirus A71 in Senegal but also point to the crucial need to set up specific surveillance programs targeting non-polio enteroviruses at country or regional levels in Africa for rapid identification emerging or re-emerging enteroviruses and better characterization of public health concerns causing acute flaccid paralysis in children such as enterovirus A71. To estimate the real distribution of EV-A71 in Africa, more sero-epidemiological studies should be promoted, particularly in countries where the virus has already been reported.

Coxsackievirus A6 Recombinant Subclades D3/A and D3/H Were Predominant in Hand-Foot-And-Mouth Disease Outbreaks in the Paediatric Population, France, 2010–2018

Coxsackievirus A6 (CVA6) emerged as the most common enterovirus of seasonal outbreaks of hand-foot-and-mouth disease (HFMD). We investigated CVA6 genetic diversity among the clinical phenotypes reported in the paediatric population during sentinel surveillance in France between 2010 and 2018. CVA6 infection was confirmed in 981 children (mean age 1.52 years [IQR 1.17–2.72]) of whom 564 (58%) were males. Atypical HFMD was reported in 705 (72%) children, followed by typical HFMD in 214 (22%) and herpangina in 57 (6%) children. Throat specimens of 245 children were processed with a target-enrichment new-generation sequencing approach, which generated 213 complete CVA6 genomes. The genomes grouped within the D1 and D3 clades (phylogeny inferred with the P1 genomic region). In total, 201 genomes were classified among the recombinant forms (RFs) A, B, F, G, H, and N, and 12 genomes were assigned to 5 previously unreported RFs (R–V). The most frequent RFs were A (58%), H (19%), G (6.1%), and F (5.2%). The yearly number of RFs ranged between 1 (in 2012 and 2013) and 6 (2018). The worldwide CVA6 epidemic transmission began between 2005 and 2007, which coincided with the global spread of the recombinant subclade D3/RF-A.

Insight into the Enterovirus A71: A review

Enterovirus A71 is a major causative pathogen of hand, foot and mouth disease. It has become a global public health threat, and is especially important for infants and young children in the Asian-Pacific countries. The enterovirus A71 is a non-enveloped virus of the Picornaviridae family having a single-stranded positive-sense RNA genome of about 7.4 kb which encodes the structural and nonstructural proteins. Currently there are no US FDA-approved vaccines or antiviral therapy available against enterovirus A71 infection. Although enterovirus A71 vaccines have been licenced in China, clinically approved vaccines for widespread vaccination programs are lacking. Substantial progress has recently been achieved on understanding the structure and function of enterovirus A71 proteins together with information on the viral genetic diversity and geographic distribution. The present review is intended to provide an overview on our current understanding of the molecular biology and epidemiology of enterovirus A71 which will aid the development of vaccines, therapeutics and other control strategies so as to bolster the preparedness for future enterovirus A71 outbreaks.

A novel subgenotype C6 Enterovirus A71 originating from the recombination between subgenotypes C4 and C2 strains in mainland China

Recombination plays important roles in the genetic diversity and evolution of Enterovirus A71 (EV-A71). The phylogenetics of EV-A71 in mainland China found that one strain DL71 formed a new subgenotype C6 with unknown origin. This study investigated the detailed genetic characteristics of the new variant. DL71 formed a distinct cluster within genotype C based on the genome and individual genes (5′UTR, VP4, VP1, 2A, 2B, 2C, 3D, and 3′UTR). The average genetic distances of the genome and individual genes (VP3, 2A, 2B, 2C, 3A, 3C, and 3D) between DL71 and reference strains were greater than 0.1. Nine recombination events involving smaller fragments along DL71 genome were detected. The strains Fuyang-0805a (C4) and Tainan/5746/98 (C2) were identified as the parental strains of DL71. In the non-recombination regions, DL71 had higher identities with Fuyang-0805a than Tainan/5746/98, and located in the cluster with C4 strains. However, in the recombination regions, DL71 had higher identities with Tainan/5746/98 than Fuyang-0805a, and located in the cluster with C2 strains. Thus, DL71 was a novel multiple inter-subgenotype recombinant derived from the dominant subgenotype C4 and the sporadic subgenotype C2 strains. Monitoring the emergence of new variants by the whole-genome sequencing remains essential for preventing disease outbreaks and developing new vaccines.

Structural basis for neutralization of enterovirus

Outbreaks of enteroviral infections are associated with morbidity and mortality in susceptible individuals worldwide. There are still no antiviral drugs or vaccines against most circulating enteroviruses. Antibody-mediated immunity is crucial for preventing and limiting enteroviral infections. In this review, we focus on enteroviruses that continue to cause endemics in recent years, such as rhinovirus, enterovirus A71, coxsackievirus, and echovirus, and introduce a structural understanding of the mechanisms of virus neutralization. The mechanisms by which virus-specific antibodies neutralize enteroviruses have been explored not only through study of viral structures, but also through understanding virus-antibody interactions at the amino acid level. Neutralizing epitopes are predominantly mapped on the canyon northern rim, canyon inner surface, canyon southern rim, and twofold and threefold plateaus of the capsid, where surface-exposed loops are located. This review also describes recent progress in deciphering the virus-receptor complex and structural rearrangements involved in the uncoating process, providing insight into plausible virus neutralization mechanisms.

Genomic surveillance of enterovirus associated with aseptic meningitis cases in southern Spain, 2015-2018

New circulating Enterovirus (EV) strains often emerge through recombination. Upsurges of recombinant non-polio enteroviruses (NPEVs) associated with neurologic manifestations such as EVA71 or Echovirus 30 (E30) are a growing public health concern in Europe. Only a few complete genomes of EVs circulating in Spain are available in public databases, making it difficult to address the emergence of recombinant EVs, understand their evolutionary relatedness and the possible implication in human disease. We have used metagenomic (untargeted) NGS to generate full-length EV genomes from CSF samples of EV-positive aseptic meningitis cases in Southern Spain between 2015 and 2018. Our analyses reveal the co-circulation of multiple Enterovirus B (EV-B) types (E6, E11, E13 and E30), including a novel E13 recombinant form. We observed a genetic turnover where emergent lineages (C1 for E6 and I [tentatively proposed in this study] for E30) replaced previous lineages circulating in Spain, some concomitant with outbreaks in other parts of Europe. Metagenomic sequencing provides an effective approach for the analysis of EV genomes directly from PCR-positive CSF samples. The detection of a novel, disease-associated, recombinant form emphasizes the importance of genomic surveillance to monitor spread and evolution of EVs.

Enterovirus Surveillance (EVSurv) in Germany

The major aim of the enterovirus surveillance (EVSurv) in Germany is to prove the absence of poliovirus circulation in the framework of the Global Polio Eradication Program (GPEI). Therefore, a free-of-charge enterovirus diagnostic is offered to all hospitals for patients with symptoms compatible with a polio infection. Within the quality proven laboratory network for enterovirus diagnostic (LaNED), stool and cerebrospinal fluid (CSF) samples from patients with suspected aseptic meningitis/encephalitis or acute flaccid paralysis (AFP) are screened for enterovirus (EV), typing is performed in all EV positive sample to exclude poliovirus infections. Since 2006, ≈200 hospitals from all 16 German federal states have participated annually. On average, 2500 samples (70% stool, 28% CSF) were tested every year. Overall, the majority of the patients studied are children <15 years. During the 15-year period, 53 different EV serotypes were detected. While EV-A71 was most frequently detected in infants, E30 dominated in older children and adults. Polioviruses were not detected. The German enterovirus surveillance allows monitoring of the circulation of clinically relevant serotypes resulting in continuous data about non-polio enterovirus epidemiology.

Seroprevalence and Virologic Surveillance of Enterovirus 71 and Coxsackievirus A6, United Kingdom, 2006-2017

Enterovirus A71 (EV-A71) and coxsackievirus A6 (CVA6) cause hand, foot and mouth disease (HFMD) and are occasionally linked to severe neurologic complications and large outbreaks worldwide. We estimated EV-A71 and CVA6 seroprevalence using cross-sectional age-stratified samples collected in 2006, 2011, and 2017. Seroprevalences of EV-A71 and CVA6 increased from 32% and 54% at 6-11 months to >75% by 10 years of age. Antibody titers declined after 20 years, which could indicate infrequent re-exposure in older populations. Age profiles for acquiring infections and mean titers were comparable in the 3 testing years, despite the marked increase in incidence of CVA6-related HFMD from 2010. The uncoupling of changes in disease severity from the infection kinetics of CVA6 as we inferred from the seroprevalence data, rather than incidence of infection over the 11-year study period, provides further evidence for a change in its pathogenicity.

First evidence of enterovirus A71 and echovirus 30 in Uruguay and genetic relationship with strains circulating in the South American region

Human enteroviruses (EVs) comprise more than 100 types of coxsackievirus, echovirus, poliovirus and numbered enteroviruses, which are mainly transmitted by the faecal-oral route leading to diverse diseases such as aseptic meningitis, encephalitis, and acute flaccid paralysis, among others. Since enteroviruses are excreted in faeces, wastewater-based epidemiology approaches are useful to describe EV diversity in a community. In Uruguay, knowledge about enteroviruses is extremely limited. This study assessed the diversity of enteroviruses through Illumina next-generation sequencing of VP1-amplicons obtained by RT-PCR directly applied to viral concentrates of 84 wastewater samples collected in Uruguay during 2011-2012 and 2017-2018. Fifty out of the 84 samples were positive for enteroviruses. There were detected 27 different types belonging to Enterovirus A species (CVA2-A6, A10, A16, EV-A71, A90), Enterovirus B species (CVA9, B1-B5, E1, E6, E11, E14, E21, E30) and Enterovirus C species (CVA1, A13, A19, A22, A24, EV-C99). Enterovirus A71 (EV-A71) and echovirus 30 (E30) strains were studied more in depth through phylogenetic analysis, together with some strains previously detected by us in Argentina. Results unveiled that EV-A71 sub-genogroup C2 circulates in both countries at least since 2011-2012, and that the C1-like emerging variant recently entered in Argentina. We also confirmed the circulation of echovirus 30 genotypes E and F in Argentina, and reported the detection of genotype E in Uruguay. To the best of our knowledge this is the first report of the EV-A71 C1-like emerging variant in South-America, and the first report of EV-A71 and E30 in Uruguay.

Genetic diversity and evolution of enterovirus A71 subgenogroup C1 from children with hand, foot, and mouth disease in Thailand

Enterovirus A71 (EV-A71) can cause hand, foot, and mouth disease (HFMD) in children and may be associated with severe neurological complications. There have been numerous reports of increased incidence of EV-A71 subgenogroup C1 (EV-A71 C1) infections associated with neurological diseases since the first occurrence in Germany in 2015. Here, we describe 11 full-length genome sequences of 2019 EV-A71 C1 strains isolated from HFMD patients in Thailand from 2019 to early 2020. The genetic evolution of 2019 EV-A71 C1 was traced in the outbreaks, and the emergence of multiple lineages was detected. Our results demonstrated that 2019 EV-A71 C1 from Thailand emerged through recombination between its nonstructural protein gene and those of other EV-A genotypes. Bayesian-based phylogenetic analysis showed that the 2019 EV-A71 C1 Thai strains share a common ancestor with variants in Europe (Denmark and France). The substitution rate for the 2019 EV-A71 C1 genome was estimated to be 4.38 × 10^-3 substitutions/(site∙year^-1) (95% highest posterior density interval: 3.84-4.94 × 10^-3 substitutions/[site∙year^-1]), approximating that observed between previous EV-A71 C1 outbreaks. These data are essential for understanding the evolution of EV-A C1 during the ongoing HFMD outbreak and may be relevant to disease outcomes in children worldwide.

Pan-Enterovirus Amplicon-Based High-Throughput Sequencing Detects the Complete Capsid of a EVA71 Genotype C1 Variant via Wastewater-Based Epidemiology in Arizona

We describe the complete capsid of a genotype C1-like Enterovirus A71 variant recovered from wastewater in a neighborhood in the greater Tempe, Arizona area (Southwest United States) in May 2020 using a pan-enterovirus amplicon-based high-throughput sequencing strategy. The variant seems to have been circulating for over two years, but its sequence has not been documented in that period. As the SARS-CoV-2 pandemic has resulted in changes in health-seeking behavior and overwhelmed pathogen diagnostics, our findings highlight the importance of wastewater-based epidemiology (WBE ) as an early warning system for virus surveillance.

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.

Emergence of genotype C1 Enterovirus A71 and its link with antigenic variation of virus in Taiwan

An outbreak of the hand-foot-mouth disease with severe neurological cases, mainly caused by the genotype C1 enterovirus A71 (EV-A71), occurred in Taiwan between 2018 and early 2019. In the recent decade, the most dominant EV-A71 genotypes in Taiwan were B5 and C4 but changed to C1 in 2018. Antibody-mediated immunity plays a key role in limiting the EV-A71 illness in humans. However, the level of neutralizing activities against genotype C1 virus by human polyclonal and monoclonal antibodies (MAbs) remains largely unclear. In the study, we demonstrated that that 39% (9 in 23) of post-infection sera from the genotype B5- or C4-infected patients in 2014–2017 exhibit reduced titers with the 2018–2019 genotype C1 viruses than with the earlier B5 and C4 viruses tested. This finding with polyclonal sera is confirmed with human MAbs derived from genotype B5 virus-infected individuals. The 2018–2019 genotype C1 virus is resistant to the majority of canyon-targeting human MAbs, which may be associated with the residue change near or at the bottom of the canyon region on the viral capsid. The remaining three antibodies (16-2-11B, 16-3-4D, and 17-1-12A), which target VP1 S241 on the 5-fold vertex, VP3 E81 on the 3-fold plateau and VP2 D84 on the 2-fold plateau of genotype C1 viral capsid, respectively, retained neutralizing activities with variable potencies. These neutralizing antibodies were also found to be protective against a lethal challenge of the 2018–2019 genotype C1 virus in an hSCARB2-transgenic mice model. These results indicate that the EV-A71-specific antibody response may consist of a fraction of poorly neutralizing antibodies against 2018–2019 genotype C1 viruses among a subset of previously infected individuals. Epitope mapping of protective antibodies that recognize the emerging genotype C1 virus has implications for anti-EV-A71 MAbs and the vaccine field.

EV-A71 is a cause of hand-foot-mouth disease, epidemics of which still regularly occur around the globe. Given that EV-A71 immune protection from the disease correlates with neutralizing antibody responses, but the responses in humans prior to an outbreak are still poorly understood. An outbreak of hand-foot-mouth disease among children emerged in Taiwan from 2018 to 2019, and genotype C1 EV-A71 caused most of the cases. Here, we characterized EV-A71-neutralizing antibody profiles in details at both the serological and monoclonal levels and showed that antibodies generated by humans prior to the emergence of genotype C1 EV-A71 less effectively neutralize C1 compared to the prior circulating genotypes, which implies the presence of antigenic variation in the EV-A71 genotypes. We further identified and mapped critical neutralizing epitopes of 2018–2019 genotype C1 EV-A71 on the top and margin of the viral capsid pentamer and demonstrated the in vivo protective effect of human monoclonal antibodies, which highlight the properties of human antibody-neutralizing sites on EV-A71 and the potential of human antibodies as antiviral agents.

Increased detection of enterovirus A71 infections, Germany, 2019

We report on the increased circulation of enterovirus A71 in Germany in 2019. Strains were mainly identified in hospitalised patients with suspected aseptic meningitis/encephalitis. Molecular analysis showed co-circulation of EV-A71 sub-genogroups C1 and C4, a signal for physicians and public health authorities to include/intensify EV diagnostic in patients showing signs of aseptic meningitis, encephalitis or acute flaccid paralysis/myelitis.

Clinical characteristics of enterovirus A71 neurological disease during an outbreak in children in Colorado, USA, in 2018: an observational cohort study

BACKGROUND

In May, 2018, Children's Hospital Colorado noted an outbreak of enterovirus A71 (EV-A71) neurological disease. We aimed to characterise the clinical features of EV-A71 neurological disease during this outbreak.

METHODS

In this retrospective observational cohort study, children (younger than 18 years) who presented to Children's Hospital Colorado (Aurora, CO, USA) between March 1 and November 30, 2018, with neurological disease (defined by non-mutually exclusive criteria, including meningitis, encephalitis, acute flaccid myelitis, and seizures) and enterovirus detected from any biological specimen were eligible for study inclusion. The clinical characteristics of children with neurological disease associated with EV-A71 were compared with those of children with neurological disease associated with other enteroviruses during the same period. To explore the differences in clinical presentation of acute flaccid myelitis, we also used a subgroup analysis to compare clinical findings in children with EV-A71-associated acute flaccid myelitis during the study period with these findings in those with enterovirus D68 (EV-D68)-associated acute flaccid myelitis at the same hospital between 2013 and 2018.

FINDINGS

Between March 10 and Nov 10, 2018, 74 children presenting to Children's Hospital Colorado were found to have enterovirus neurological disease; EV-A71 was identified in 43 (58%) of these children. The median age of the children with EV-A71 neurological disease was 22·7 months (IQR 4·0-31·9), and most of these children were male (34 [79%] children). 40 (93%) children with EV-A71 neurological disease had findings suggestive of meningitis, 31 (72%) children showed evidence of encephalitis, and ten (23%) children met our case definition of acute flaccid myelitis. All children with EV-A71 disease had fever and 18 (42%) children had hand, foot, or mouth lesions at or before neurological onset. Children with EV-A71 disease were best differentiated from those with other enteroviruses (n=31) by the neurological findings of myoclonus, ataxia, weakness, and autonomic instability. Of the specimens collected from children with EV-A71, this enterovirus was detected in 94% of rectal, 79% of oropharyngeal, 56% of nasopharyngeal, and 20% of cerebrospinal fluid specimens. 39 (93%) of 42 children with EV-A71 neurological disease who could be followed up showed complete recovery by 1-2 months. Compared with children with EV-D68-associated acute flaccid myelitis, children with EV-A71-associated acute flaccid myelitis were younger, showed neurological onset earlier after prodromal symptom onset, had milder weakness, showed more rapid improvement, and were more likely to completely recover.

INTERPRETATION

This outbreak of EV-A71 neurological disease, the largest reported in the Americas, was characterised by fever, myoclonus, ataxia, weakness, autonomic instability, and full recovery in most patients. Because EV-A71 epidemiology outside of Asia remains difficult to predict, identification of future outbreaks will be aided by prompt recognition of these distinct clinical findings, testing of non-sterile and sterile site specimens, and enhanced enterovirus surveillance.

FUNDING

None.

Characterization of a novel echovirus 21 strain isolated from a healthy child in China in 2013

Echovirus 21 (E21) belongs to the species Enterovirus B, whose members are frequently associated with acute flaccid paralysis. E21 strain 553/YN/CHN/2013 was isolated from a healthy child in Yunnan, China, in 2013. This is the first report of the complete genome sequence of E21 in China. This strain shared 81.7% nucleotide sequence identity and 96.8% amino acid sequence identity with the E21 prototype strain Farina. Although strain 553/YN/CHN/2013 belongs to the E21 serotype, the only similarity to the E21 strain was in the VP1 region, as other genomic regions, including VP2-VP4, were more similar to other EV-B members. Recombination analysis showed evidence of recombination events between E21 and other EV-B viruses. E21 strain 553/YN/CHN/2013 failed to infect suckling mice via intracerebral injection. Surveillance of E21 is very important to help forecast the potential of emerging E21 outbreaks and related diseases.

Next generation sequencing of human enterovirus strains from an outbreak of enterovirus A71 shows applicability to outbreak investigations

BACKGROUND

The most recent documented Australian outbreak of enterovirus A71 (EV-A71) occurred in Sydney from 2012 to 2013. Over a four-month period more than 100 children presented to four paediatric hospitals with encephalitic presentations including fever and myoclonic jerks. The heterogeneous presentations included typical encephalomyelitis, and cardiopulmonary complications.

OBJECTIVES

To characterise the genomes of enterovirus strains circulating during the 2013 Sydney EV-A71 outbreak and determine their phylogeny, phylogeography and association between genome and clinical phenotype.

STUDY DESIGN

We performed an analysis of enterovirus (EV) positive specimens from children presenting to hospitals in the greater Sydney region of Australia during the 2013 outbreak. We amplified near full-length genomes of EV, and used next generation sequencing technology to sequence the virus. We used phylogenetic/phylogeographic analysis to characterize the outbreak viruses.

RESULTS

We amplified and sequenced 23/63 (37 %) genomes, and identified the majority (61 %) as EV-A71. The EV-A71 sequences showed high level sequence homology to C4a genogroups of EV-A71 circulating in China and Vietnam during 2012-13. Phylogenetic analysis showed EV-A71 strains associated with more severe symptoms, including encephalitis or cardiopulmonary failure, grouped together more closely than those from patients with hand, foot and mouth disease. Amongst the non-EV-A71 sequences were five other EV subtypes (representing enterovirus subtypes A and B), reflecting the diversity of EV co-circulation within the community.

CONCLUSIONS

This is the first Australian study investigating the near full-length genome of EV strains identified during a known outbreak of EV-A71. EV-A71 sequences were very similar to strains circulating in Asia during the same time period. Whole genome sequencing offers additional information over routine diagnostic testing such as characterisation of emerging recombinant strains and inform vaccine design.