Upsurge of human enterovirus 68 infections in patients with severe respiratory tract infections

Enterovirus-D68 - A Reemerging Non-Polio Enterovirus that Causes Severe Respiratory and Neurological Disease in Children

The past decade has seen the global reemergence and rapid spread of enterovirus D68 (EV-D68), a respiratory pathogen that causes severe respiratory illness and paralysis in children. EV-D68 was first isolated in 1962 from children with pneumonia. Sporadic cases and small outbreaks have been reported since then with a major respiratory disease outbreak in 2014 associated with an increased number of children diagnosed with polio-like paralysis. From 2014-2018, major outbreaks have been reported every other year in a biennial pattern with > 90% of the cases occurring in children under the age of 16. With the outbreak of SARS-CoV-2 and the subsequent COVID-19 pandemic, there was a significant decrease in the prevalence EV-D68 cases along with other respiratory diseases. However, since the relaxation of pandemic social distancing protocols and masking mandates the number of EV-D68 cases have begun to rise again - culminating in another outbreak in 2022. Here we review the virology, pathogenesis, and the immune response to EV-D68, and discuss the epidemiology of EV-D68 infections and the divergence of contemporary strains from historical strains. Finally, we highlight some of the key challenges in the field that remain to be addressed.

Enterovirus D-68 Infection of Primary Rat Cortical Neurons: Entry, Replication, and Functional Consequences

Enterovirus D68 (EV-D68) is an emerging pathogen associated with mild to severe respiratory disease. Since 2014, EV-D68 is also linked to acute flaccid myelitis (AFM), causing paralysis and muscle weakness in children. However, it remains unclear whether this is due to an increased pathogenicity of contemporary EV-D68 clades or increased awareness and detection of this virus. Here, we describe an infection model of primary rat cortical neurons to study the entry, replication, and functional consequences of different EV-D68 strains, including historical and contemporary strains. We demonstrate that sialic acids are important (co)receptors for infection of both neurons and respiratory epithelial cells. Using a collection of glycoengineered isogenic HEK293 cell lines, we show that sialic acids on either N-glycans or glycosphingolipids can be used for infection. Additionally, we show that both excitatory glutamatergic and inhibitory GABA-ergic neurons are susceptible and permissive to historical and contemporary EV-D68 strains. EV-D68 infection of neurons leads to the reorganization of the Golgi-endomembranes forming replication organelles, first in the soma and later in the processes. Finally, we demonstrate that the spontaneous neuronal activity of EV-D68-infected neuronal network cultured on microelectrode arrays (MEA) is decreased, independent of the virus strain. Collectively, our findings provide novel insights into neurotropism and -pathology of different EV-D68 strains, and argue that it is unlikely that increased neurotropism is a recently acquired phenotype of a specific genetic lineage. IMPORTANCE Acute flaccid myelitis (AFM) is a serious neurological illness characterized by muscle weakness and paralysis in children. Since 2014, outbreaks of AFM have emerged worldwide, and they appear to be caused by nonpolio enteroviruses, particularly enterovirus-D68 (EV-D68), an unusual enterovirus that is known to mainly cause respiratory disease. It is unknown whether these outbreaks reflect a change of EV-D68 pathogenicity or are due to increased detection and awareness of this virus in recent years. To gain more insight herein, it is crucial to define how historical and circulating EV-D68 strains infect and replicate in neurons and how they affect their physiology. This study compares the entry and replication in neurons and the functional consequences on the neural network upon infection with an old "historical" strain and contemporary "circulating" strains of EV-D68.

An increase in enterovirus D68 circulation and viral evolution during a period of increased influenza like illness, The Johns Hopkins Health System, USA, 2022

BACKGROUND

An increase in influenza like illness in children and adolescents at the Johns Hopkins Health system during summer 2022 was associated with increased positivity for enterovirus/ rhinovirus. We sought to characterize the epidemiology and viral evolution of enterovirus D68 (EV-D68).

METHODS

A cohort of remnant respiratory samples tested at the Johns Hopkins Microbiology Laboratory was screened for EV-D68. EV-D68 positives were characterized by whole genome sequencing and viral loads were assessed by droplet digital PCR (ddPCR). Genomic changes and viral loads were analyzed along with patients' clinical presentations.

RESULTS

Of 566 screened samples, 126 were EV-D68 (22.3%). The median age of EV-D68 infected patients was four years, a total of 52 required supplemental oxygen (41.3%), and 35 (27.8%) were admitted. Lung disease was the most frequent comorbidity that was associated with hospitalization. A total of 75 complete and 32 partial genomes were characterized that made a new cluster within the B3 subclade that was closest to US genomes from 2018. Amino acid changes within the BC and DE loops were identified from 31 genomes (29%) which correlated with an increase in average viral load in respiratory specimens and the need for supplemental oxygen.

CONCLUSIONS

EV-D68 outbreaks continue to cause influenza like illness that could be overwhelming for the health system due to a significant demand for high flow oxygen. Viral evolution and an increase in the susceptible population are likely driving the trends of the increased EV-D68 infections.

Off-season circulation and characterization of enterovirus D68 with respiratory and neurological presentation using whole-genome sequencing

To explore an off-season enterovirus D68 (EV-D68) upsurge in the winter season of 2019/2020, we adapted a whole-genome sequencing approach for Nanopore Sequencing for 20 hospitalized patients with accompanying respiratory or neurological presentation. Applying phylodynamic and evolutionary analysis on Nextstrain and Datamonkey respectively, we report a highly diverse virus with an evolutionary rate of 3.05 × 10^-3 substitutions per year (entire EV-D68 genome) and a positive episodic/diversifying selection with persistent yet undetected circulation likely driving evolution. While the predominant B3 subclade was identified in 19 patients, one A2 subclade was identified in an infant presenting with meningitis. Exploring single nucleotide variations using CLC Genomics Server showed high levels of non-synonymous mutations, particularly in the surface proteins, possibly highlighting growing problems with routine Sanger sequencing for typing enteroviruses. Surveillance and molecular approaches to enhance current knowledge of infectious pathogens capable of pandemic potential are paramount to early warning in health care facilities.

Enterovirus D68 in Hospitalized Children, Barcelona, Spain, 2014-2021

To determine molecular epidemiology and clinical features of enterovirus D68 (EV-D68) infections, we reviewed EV-D68–associated respiratory cases at a hospital in Barcelona, Spain, during 2014–2021. Respiratory samples were collected from hospitalized patients or outpatients with symptoms of acute respiratory tract infection or suggestive of enterovirus infection. Enterovirus detection was performed by real-time multiplex reverse transcription PCR and characterization by phylogenetic analysis of the partial viral protein 1 coding region sequences. From 184 patients with EV-D68 infection, circulating subclades were B3 (80%), D1 (17%), B2 (1%), and A (<1%); clade proportions shifted over time. EV-D68 was detected mostly in children (86%) and biennially (2016, 2018, 2021). In patients <16 years of age, the most common sign/symptom was lower respiratory tract infection, for which 11.8% required pediatric intensive care unit admission and 2.3% required invasive mechanical ventilation; neurologic complications developed in 1. The potential neurotropism indicates that enterovirus surveillance should be mandatory.

Evolution, geographic spreading, and demographic distribution of Enterovirus D68

Worldwide outbreaks of enterovirus D68 (EV-D68) in 2014 and 2016 have caused serious respiratory and neurological disease. We collected samples from several European countries during the 2018 outbreak and determined 53 near full-length genome (‘whole genome’) sequences. These sequences were combined with 718 whole genome and 1,987 VP1-gene publicly available sequences. In 2018, circulating strains clustered into multiple subgroups in the B3 and A2 subclades, with different phylogenetic origins. Clusters in subclade B3 emerged from strains circulating primarily in the US and Europe in 2016, though some had deeper roots linking to Asian strains, while clusters in A2 traced back to strains detected in East Asia in 2015-2016. In 2018, all sequences from the USA formed a distinct subgroup, containing only three non-US samples. Alongside the varied origins of seasonal strains, we found that diversification of these variants begins up to 18 months prior to the first diagnostic detection during a EV-D68 season. EV-D68 displays strong signs of continuous antigenic evolution and all 2018 A2 strains had novel patterns in the putative neutralizing epitopes in the BC- and DE-loops. The pattern in the BC-loop of the USA B3 subgroup had not been detected on that continent before. Patients with EV-D68 in subclade A2 were significantly older than patients with a B3 subclade virus. In contrast to other subclades, the age distribution of A2 is distinctly bimodal and was found primarily among children and in the elderly. We hypothesize that EV-D68’s rapid evolution of surface proteins, extensive diversity, and high rate of geographic mixing could be explained by substantial reinfection of adults. Better understanding of evolution and immunity across diverse viral pathogens, including EV-D68 and SARS-CoV-2, is critical to pandemic preparedness in the future.

Enterovirus D68 (EV-D68) has caused punctuated, global outbreaks of respiratory illness and neurological disease, including being implicated as the cause of acute flaccid myelitis (AFM). Serology studies and surveillance data suggests almost everyone is infected during early childhood. The majority of sequences collected are from young children, while adults retain high antibody titers against strains that circulated when they were young. However, little is known about how outbreaks are connected and how the virus evolves and spreads around the globe. Despite EV-D68’s apparent reliance on young, naive hosts, EV-D68 antibody binding sites are reportedly evolving under antigenic pressure, and EV-D68 seems to spread rapidly during outbreaks. In this multi-center European collaboration, we confirm that subclade specific age differences are present in those infected. Further, we were able to quantify between- and within-country migration and the ‘hidden’ diversification that indicates unsampled circulation between outbreaks. We conclude that the evolution of EV-D68 may be driven by substantial re-infection of adults, explaining the rapid geographic mixing and continuous antigenic evolution. The presence of largely unsampled circulation prior to outbreaks suggests there are gaps in current surveillance practices which could be addressed by expanding genetic surveillance.

Enterovirus D68 Protease 2Apro Targets TRAF3 To Subvert Host Innate Immune Responses

Human enterovirus D68 (EV-D68) has received considerable attention recently as a global reemergent pathogen because it causes severe respiratory tract infections and acute flaccid myelitis (AFM). The nonstructural protein 2A protease (2A^pro) of EVs, which functions in the cleavage of host proteins, comprises a pivotal part of the viral immune evasion process. However, the pathogenic mechanism of EV-D68 is not fully understood. In this study, we found that EV-D68 inhibited antiviral type I interferon responses by cleaving tumor necrosis factor receptor-associated factor 3 (TRAF3), which is the key factor for type I interferon production. EV-D68 inhibited Sendai virus (SEV)-induced interferon regulatory factor 3 (IRF3) activation and beta interferon (IFN-β) expression in HeLa and HEK293T cells. Furthermore, we demonstrated that EV-D68 and 2A^pro were able to cleave the C-terminal region of TRAF3 in HeLa and HEK293T cells, respectively. A cysteine-to-alanine substitution at amino acid 107 (C107A) in the 2A^pro protease resulted in the loss of cleavage activity to TRAF3, and mutation of glycine at amino acid 462 to alanine (G462A) in TRAF3 conferred resistance to 2A^pro These results suggest that control of TRAF3 by 2A^pro may be a mechanism EV-D68 utilizes to subvert host innate immune responses.IMPORTANCE Human enterovirus 68 (EV-D68) has received considerable attention recently as a global reemergent pathogen because it causes severe respiratory tract infections and acute flaccid myelitis. The nonstructural protein 2A protease (2A^pro) of EV, which functions in cleavage of host proteins, comprises an essential part of the viral immune evasion process. However, the pathogenic mechanism of EV-D68 is not fully understood. Here, we show for the first time that EV-D68 inhibited antiviral type I interferon responses by cleaving tumor necrosis factor receptor-associated factor 3 (TRAF3). Furthermore, we identified the key cleavage site in TRAF3. Our study may suggest a new mechanism by which the 2A^pro of EV facilitates subversion of host innate immune responses. These findings increase our understanding of EV-D68 infection and may help identify new antiviral targets against EV-D68.

Frequent detection of enterovirus D68 and rhinovirus type C in children with acute respiratory infections

This study aimed to evaluate the prevalence of human rhinoviruses (HRVs) and the emergence of enterovirus D68 (EV-D68) in children. A total of 322 nasopharyngeal swab samples were provided from children with an initial diagnosis of upper and lower respiratory tract infections. A total of 34 and 70 cases were positive for EV-D68 and HRV, respectively. The phylogenetic analysis revealed that the clades A and B are the prevalent genotypes for EV-D68 and the HRV-positive samples belong to three types including HRV-A, HRV-B, and HRV-C. The results showed that EV-D68 and HRV-C are circulating in Iran especially in the winter.

Enterovirus D68 serosurvey: evidence for endemic circulation in the Netherlands, 2006 to 2016

BackgroundEnterovirus D68 (EV-D68) has caused major outbreaks of severe respiratory illness worldwide since 2010.AimOur aim was to evaluate EV-D68 circulation in the Netherlands by conducting a serosurvey of EV-D68 neutralising antibodies (nAb) among the Dutch general population.MethodsWe screened 280 sera from children and adults in the Netherlands and used two independent sets of samples collected in the years 2006 and 2007 and in the years 2015 and 2016, time points before and after the first EV-D68 upsurge in 2010. Neutralisation capacity of the sera was tested against the prototype Fermon EV-D68 strain isolated in 1962 and against a recent EV-D68 strain (genotype B3) isolated in France in 2016.ResultsRegardless of the time of serum collection, we found remarkably high overall seropositivity (94.3-98.3%) for nAb against both EV-D68 strains. Geometric mean titres increased in an age-dependent manner.ConclusionsOur data suggest that EV-D68 has been circulating in the Netherlands for decades and that the enterovirus surveillance does not accurately capture the prevalence of this clinically relevant pathogen.

Respiratory presentation of patients infected with enterovirus D68 in Taiwan

BACKGROUND

Enterovirus-D68 (EV-D68) has been endemic in Taiwan for some years with a small number of positive cases. Detailed information about respiratory presentation is lacking. This study characterized the clinical course in children admitted to the medical center and regional hospital in Taichung during 2015.

METHODS

Retrospective chart review of patients with confirmed EV-D68 infection admitted to the medical center and regional hospital in Taichung with respiratory symptoms in the second half of 2015. Past medical history, clinical presentation, management, and course in hospital were collected and analyzed. Simple demographic data and clinical symptoms were also collected from patients confirmed with EV-D68 infection who visited clinics in Taichung.

RESULTS

Six children were included. Two patients had a prior history of asthma or recurrent dyspnea, and one had other preexisting medical comorbidities. One child was admitted to the pediatric intensive care unit. All the patients were cured. Cough, rhinorrhea, tachypnea and fever were the most common clinical symptoms among inpatients, while influenza-like illness (ILI) was prevalent in outpatients.

CONCLUSION

EV-D68 infection resulted in respiratory presentations of asthma-like illness in the hospitalized pediatric population. Patients with a prior history of asthma or recurrent dyspnea appear to be more severely affected.

Current status of enterovirus D68 worldwide and in Taiwan

Enterovirus D68 was first identified in 1962 and caused a worldwide outbreak starting from the North America in 2014. Enterovirus D68 has been in continuous circulation among many countries recently, including Taiwan. Reports also reveal high seroprevalence, which indicates that the disease burden of enterovirus D68 may be underestimated via viral culture or polymerase chain reaction results. Although most infected cases have mild respiratory illness, severe complications including acute flaccid myelitis and acute respiratory distress syndrome have also been reported. In the position of an emerging pathogen, enterovirus D68 poses a threat to public health and may cause devastating diseases. Diverse severity of neurological sequelae remains inevitable among acute flaccid myelitis patients, but no curable treatment is available currently. According to the management suggestions of the American Centers of Disease Control, uses of corticosteroids and plasmapheresis are either preferred or avoided and intravenous immunoglobulin also has no clear indication in the treatment for acute flaccid myelitis. In this review article, we provide information about the epidemiology, clinical recognition and treatment strategy of enterovirus D68. Better understanding of this disease is the foothold for advanced investigation and monitoring in the future.

Performance evaluation of the Panther Fusion® respiratory tract panel

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Clinical specificity of Panther Fusion® is between 96 %–100 %, compared to LDT.

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Clinical sensitivity Panther Fusion® is between 71.9 %–100 %, compared to LDT.

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Overall linear regression showed good correlations between LDT and Panther Fusion® for all viruses, except RV and PIV-4.

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The Panther Fusion® provides a random-access system with continuous loading and shorter sample-to-answer times compared to LDT.

Background

Respiratory tract infections are among the most common infections during winter season. Rapid diagnostics is required for clinical decision making regarding isolation of patients and appropriate therapy.

Objectives

The aim of this study was to evaluate the analytical and clinical performance characteristics of the Panther Fusion® respiratory panel using published laboratory-developed real-time PCR assays (LDT).

Study design

Analytical sensitivity of Panther Fusion® Flu A/B/RSV was assessed by testing dilutions of cell culture isolates. Clinical performance assessment included the complete Panther Fusion® respiratory panel (Flu-A/B/RSV, PIV 1-4 and AdV/hMPV/RV) and consisted of a retrospective and a prospective study-arm. The retrospective evaluation included 201, stored (−80 °C) samples collected between February 2006 and January 2017. Prospective evaluation was performed on 1045 unselected pretreated respiratory tract samples from patients presented to our hospital between November 2017 and May 2018.

Results

Analytical sensitivity was generally slightly lower for the Panther Fusion® assays. Clinical specificity and sensitivity was between 96 %–100 % and 71.9 %–100 %, respectively. Discrepant results were found in 146 samples of which 88 samples tested LDT positive / Panther Fusion® negative and 58 samples were LDT negative / Panther Fusion® positive. A total of ten discrepant samples with Ct-values <30 were sequenced to confirm the presence of 7 RV-C not-detected by LDT and 1 RV-A and 2 ADV-2 not detected by Panther Fusion®.

Conclusions

The Panther Fusion® provides a random-access system with continuous loading and much shorter sample-to-answer times compared to LDT, albeit with a slightly less clinical sensitivity compared to the LDT.

Association of Enterovirus D68 with Acute Flaccid Myelitis, Philadelphia, Pennsylvania, USA, 2009-2018

Acute flaccid myelitis (AFM) is a polio-like disease that results in paralysis in previously healthy persons. Although the definitive cause of AFM remains unconfirmed, enterovirus D68 (EV-D68) is suspected based on 2014 data demonstrating an increase in AFM cases concomitant with an EV-D68 outbreak. We examined the prevalence in children and the molecular evolution of EV-D68 for 2009–2018 in Philadelphia, Pennsylvania, USA. We detected widespread EV-D68 circulation in 2009, rare detections in 2010 and 2011, and then biennial circulation, only in even years, during 2012–2018. Prevalence of EV-D68 significantly correlated with AFM cases during this period. Finally, whole-genome sequencing revealed early detection of the B1 clade in 2009 and continued evolution of the B3 clade from 2016 to 2018. These data reinforce the need to improve surveillance programs for nonpolio enterovirus to identify possible AFM triggers and predict disease prevalence to better prepare for future outbreaks.

Understanding Enterovirus D68-Induced Neurologic Disease: A Basic Science Review

In 2014, the United States (US) experienced an unprecedented epidemic of enterovirus D68 (EV-D68)-induced respiratory disease that was temporally associated with the emergence of acute flaccid myelitis (AFM), a paralytic disease occurring predominantly in children, that has a striking resemblance to poliomyelitis. Although a definitive causal link between EV-D68 infection and AFM has not been unequivocally established, rapidly accumulating clinical, immunological, and epidemiological evidence points to EV-D68 as the major causative agent of recent seasonal childhood AFM outbreaks in the US. This review summarizes evidence, gained from in vivo and in vitro models of EV-D68-induced disease, which demonstrates that contemporary EV-D68 strains isolated during and since the 2014 outbreak differ from historical EV-D68 in several factors influencing neurovirulence, including their genomic sequence, their receptor utilization, their ability to infect neurons, and their neuropathogenicity in mice. These findings provide biological plausibility that EV-D68 is a causal agent of AFM and provide important experimental models for studies of pathogenesis and treatment that are likely to be difficult or impossible in humans.

Susceptibility of Enterovirus-D68 to RNAi-mediated antiviral knockdown

Enterovirus D68 (EV-D68) represents an emerging pathogen which has demonstrated a capacity for causing epidemic illness in pediatric and immunocompromised patients. With no effective antiviral treatment available, therapeutic interventions are currently limited to supportive care. Utilizing available genomic sequences from the 2014 B3 Epidemic EV-D68 clade and the 1962 Fermon EV-D68 strains, we performed in silico comparative genomic analysis, identifying several islands of phylogenetic conservation within the viral RNA-dependent RNA polymerase gene. The effects of transfecting short-interfering double-stranded RNA (siRNA) molecules targeting these conserved sequences were tested in vitro using a human rhabdomyosarcoma cell-based model of EV-D68 infection. Two siRNA sequences demonstrated reproducible ability to abrogate EV-D68-mediated cytopathic effect in vitro. These siRNA sequences were also able to decrease EV-D68 genome replication, VP-2 capsid protein expression, and infectious particle production in vitro. EV-D68 knockdown was sequence-specific and not observed in cells treated with a negative control siRNA lacking sequence homology to the viral genome. The regions targeted by these siRNA's are located in highly conserved regions of the RNA-dependent RNA polymerase gene. The most potent siRNA targeted a sequence found in subsequent enzyme crystallographic studies to enhance the enzyme's thermostability (Wang et al., 2017). Topical nebulized siRNAs have recently been utilized as antivirals in human studies, with no adverse effects or toxicities noted (Gottlieb et al., 2016). Sequence selection is likely one primary factor determining the potential efficacy of such therapeutics. These results demonstrate that the identified siRNA sequences are able to suppress EV-D68 replication and cytopathic effect in vitro.

Twenty-nine Cases of Enterovirus-D68-associated Acute Flaccid Myelitis in Europe 2016: A Case Series and Epidemiologic Overview

BACKGROUND

Enterovirus-D68 (EV-D68) is a respiratory virus within the genus Enterovirus and the family of Picornaviridae. Genetically, it is closely related to rhinovirus that replicates in the respiratory tract and causes respiratory disease. Since 2014, EV-D68 has been associated with the neurologic syndrome of acute flaccid myelitis (AFM).

METHODS

In October 2016, questionnaires were sent out to a European network including 66 virologists and clinicians, to develop an inventory of EV-D68-associated AFM cases in Europe. Clinical and virologic information of case patients was requested. In addition, epidemiologic information on EV testing was collected for the period between March and October 2016.

RESULTS

Twenty-nine cases of EV-D68-associated AFM were identified, from 12 different European countries. Five originated from France, 5 from Scotland and 3 each from Sweden, Norway and Spain. Twenty-six were children (median age 3.8 years), 3 were adults. EV-D68 was detected in respiratory materials (n = 27), feces (n = 8) and/or cerebrospinal fluid (n = 2). Common clinical features were asymmetric flaccid limb weakness, cranial nerve deficits and bulbar symptoms. On magnetic resonance imaging, typical findings were hyperintensity of the central cord and/or brainstem; low motor amplitudes with normal conduction velocities were seen on electromyography. Full clinical recovery was rare (n = 3), and 2 patients died. The epidemiologic data from 16 European laboratories showed that of all EV-D68-positive samples, 99% was detected in a respiratory specimen.

CONCLUSIONS

For 2016, 29 EV-D68-related AFM cases were identified in mostly Western Europe. This is likely an underestimation, because case identification is dependent on awareness among clinicians, adequate viral diagnostics on respiratory samples and the capability of laboratories to type EVs.

A neonatal mouse model of Enterovirus D68 infection induces both interstitial pneumonia and acute flaccid myelitis

Enterovirus D68 (EV-D68) is a causative agent of recent outbreaks of severe respiratory illness, pneumonia and acute flaccid myelitis (AFM) worldwide. The study of the pathogenesis, vaccines and anti-viral drugs for EV-D68 infection has been reported. Given the previously described mouse model of EV-D68, we sought to establish a neonatal mice model inducing both pneumonia and AFM. The neonatal BALB/c mice were inoculated intraperitoneally with the EV-D68 strain (named15296-virus) which was produced by the reverse genetics method. The infected mice displayed limb paralysis, tachypnea and even death, which were similar to the clinical symptoms of human infections. Moreover, the results of histopathologic examination and immunohistochemical staining showed acidophilic necrosis in the muscle, the spinal cord and alveolar wall thickening in the lung, indicating that EV-D68 exhibited strong tropism to the muscles, spinal cord and lung. Furthermore, the results of real-time PCR also suggested that the viral loads in the blood, spinal cord, muscles and lung were higher than those in other tissues at different time points post-infection. Additionally, the neonatal mouse model was used for evaluating the EV-D68 infection. The results of the anti-serum passive and maternal antibody protection indicated that the neonatal mice could be protected against the EV-D68 challenge, and displayed that both the serum of 15296-virus and prototype-virus (Fermon) were performing a certain cross-protective activity against the 15296-virus challenge. In summary, the above results proved that our neonatal mouse model possessed not only the interstitial pneumonia and AFM simultaneously but also a potentiality to evaluate the protective effects of EV-D68 vaccines and anti-viral drugs in the future.

Enterovirus D68 - The New Polio?

Enterovirus D68 (EV-D68) has emerged over the recent years, with large outbreaks worldwide. Increased occurrence has coincided with improved clinical awareness and surveillance of non-polio enteroviruses. Studies showing its neurotropic nature and the change in pathogenicity have established EV-D68 as a probable cause of Acute Flaccid Myelitis (AFM). The EV-D68 storyline shows many similarities with poliovirus a century ago, stimulating discussion whether EV-D68 could be ascertaining itself as the "new polio." Increasing awareness amongst clinicians, incorporating proper diagnostics and integrating EV-D68 into accessible surveillance systems in a way that promotes data sharing, will be essential to reveal the burden of disease. This will be a necessary step in preventing EV-D68 from becoming a threat to public health.

Clinical characteristics of children infected with enterovirus D68 in an outpatient clinic and the association with bronchial asthma

BACKGROUND

All reports of increases in severe respiratory disease associated with human enterovirus D68 (EV-D68) are from hospital settings. However, there are few reports describing clinical characteristics in less severely affected populations.

METHODS

We conducted a retrospective observational study from January 2010 to December 2015 in Yamagata, Japan. Using regional passive surveillance, 5794 respiratory specimens were collected from children who initially presented to an outpatient clinic with acute respiratory symptoms. The collected samples were tested for EV-D68 by reverse transcription PCR.

RESULTS

EV-D68 was detected in 79 specimens mainly during the two epidemic periods in August-October 2010 and August-October 2015, when detection rates were 10.2% (31 of 304 specimens) and 16.3% (46 of 282 specimens), respectively. Among the 69 EV-D68-positive children, excluding those with viral coinfection, 39 (57%) had upper respiratory tract infections, 23 (33%) bronchiolitis or asthma attack, 5 (7%) bronchitis, 1 (1%) meningitis and 1 (1%) acute flaccid paralysis. In 23 children with wheezing, retraction was observed in 10 (43%), and six (26%) were diagnosed with asthma exacerbation. Six children required hospital admission, five (83%) because of asthma exacerbation. A history of asthma or wheezing was the most significant risk factor for the development of wheezing (odds ratio, 8.23; 95% CI, 2.65-25.50; p < .001).

CONCLUSIONS

The low rate of hospitalization (9%, 6 of 69) indicates that most cases with EV-D68 infection were managed as outpatients. A history of asthma or wheezing was a potential risk factor for wheezing, resulting in hospitalization due to a severe asthma attack.

VIRO-TypeNed, systematic molecular surveillance of enteroviruses in the Netherlands between 2010 and 2014

VIRO-TypeNed is a collaborative molecular surveillance platform facilitated through a web-based database. Genetic data in combination with epidemiological, clinical and patient data are shared between clinical and public health laboratories, as part of the surveillance underpinning poliovirus eradication. We analysed the combination of data submitted from 2010 to 2014 to understand circulation patterns of non-polio enteroviruses (NPEV) of public health relevance. Two epidemiological patterns were observed based on VIRO-TypeNed data and classical surveillance data dating back to 1996: (i) endemic cyclic, characterised by predictable upsurges/outbreaks every two to four years, and (ii) epidemic, where rare virus types caused upsurges/outbreaks. Genetic analysis suggests continuous temporal displacement of virus lineages due to the accumulation of (silent) genetic changes. Non-synonymous changes in the antigenic B/C loop suggest antigenic diversification, which may affect population susceptibility. Infections were frequently detected at an age under three months and at an older, parenting age (25–49 years) pointing to a distinct role of immunity in the circulation patterns. Upsurges were detected in the summer and winter which can promote increased transmissibility underlying new (cyclic) upsurges and requires close monitoring. The combination of data provide a better understanding of NPEV circulation required to control and curtail upsurges and outbreaks.

Epidemiological and clinical characteristics of patients infected with enterovirus D68, France, July to December 2014

In 2014, the United States (US) experienced a nationwide outbreak of enterovirus D68 (EV-D68) infection with 1,152 cases reported mainly in hospitalised children with severe asthma or bronchiolitis. Following the US alert, 11 laboratories of the French enterovirus (EV) surveillance network participated in an EV-D68 survey. A total of 6,229 respiratory samples, collected from 1 July to 31 December 2014, were screened for EV-D68 resulting in 212 EV-D68-positive samples. These 212 samples corresponded to 200 EV-D68 cases. The overall EV-D68 positivity rates among respiratory samples were of 5% (184/3,645) and 1.1% (28/2,584) in hospitalised children and adults respectively. The maximum weekly EV-D68 positivity rates were of 16.1% for children (n = 24/149; week 43) and 2.6% for adults (n = 3/115; week 42). Of 173 children with EV-D68 infection alone, the main symptoms were asthma (n = 83; 48.0%) and bronchiolitis (n = 37; 21.4%). One child developed acute flaccid paralysis (AFP) following EV-D68-associated pneumonia. Although there was no significant increase in severe respiratory tract infections reported to the French public health authorities, 10.7% (19/177) of the EV-D68 infected children and 14.3% (3/21) of the EV-D68 infected adults were hospitalised in intensive care units. Phylogenetic analysis of the viral protein 1 (VP1) sequences of 179 EV-D68 cases, revealed that 117 sequences (65.4%), including that of the case of AFP, belonged to the B2 variant of clade B viruses. Continuous surveillance of EV-D68 infections is warranted and could benefit from existing influenza-like illness and EV surveillance networks.

Clinical Course of Enterovirus D68 in Hospitalized Children

BACKGROUND

Enterovirus D68 (EV-D68) has been sporadically reported as a cause of respiratory tract infections. In 2014, an international outbreak of EV-D68 occurred and caused severe respiratory disease in the pediatric population.

METHODS

A retrospective chart review was performed of children admitted to Children's Mercy Hospital from August 1, 2014, to September 15, 2014, with positive multiplex polymerase chain reaction testing for EV/rhinovirus (RV). Specimens were subsequently tested for EV-D68, and clinical data were obtained from the medical records. Patients with EV-D68 were compared with children presenting simultaneously with other EV/RV.

RESULTS

Of 542 eligible specimens, children with EV-D68 were significantly older than children with other EV/RV (4.6 vs. 2.2 years, P < 0.001). Children with EV-D68 were more likely to have a history of asthma (38.6% vs. 30.0%, P = 0.04) or recurrent wheezing (22.1% vs. 14.8%, P = 0.04). EV-D68-positive children more commonly received supplemental oxygen (86.7% vs. 65.0%, P < 0.001), albuterol (91.2% vs. 65.5%, P < 0.001) and corticosteroids (82.9% vs. 58.6%, P < 0.001). Age ≥5 years was an independent risk factor for intensive care unit management in EV-D68-infected children. Children with a history of asthma or recurrent wheezing and EV-D68 received supplemental oxygen (92.7% vs. 82.4%, P = 0.007) and magnesium (42.7% vs. 29.7%, P = 0.03) at higher rates and more continuous albuterol (3 vs. 2 hours, P = 0.03) than those with other EV/RV.

CONCLUSIONS

EV-D68 causes severe disease in the pediatric population, particularly in children with a history of asthma or recurrent wheezing. EV-D68-positive children are more likely to require therapy for refractory bronchospasm and may need intensive care unit- level care.

Global Distribution and Evolutionary History of Enterovirus D68, with Emphasis on the 2014 Outbreak in Ontario, Canada

Despite its first appearance in 1962, human enterovirus D68 (EV-D68) has been recognized as an emerging respiratory pathogen in the last decade when it caused outbreaks and clusters in several countries including Japan, the Philippines, and the Netherlands. The most recent and largest outbreak of EV-D68 associated with severe respiratory illness took place in North America between August 2014 and January 2015. Between September 1 and October 31 2014, EV-D68 infection was laboratory confirmed among 153/907 (16.9%) persons tested for the virus in Ontario, Canada, using real time RT-PCR and subsequent genotyping by sequencing of partial VP1 gene. In order to understand the evolutionary history of the 2014 North American EV-D68 outbreak, we conducted phylogenetic and phylodynamic analyses using available partial VP1 genes (n = 469) and NCBI available whole genome sequences (WGS) (n = 38). The global EV-D68 phylogenetic tree (n = 469) reconfirms the divergence of three distinct clades A, B, and C from the prototype EV-D68 Fermon strain as previously documented. Two sub-clades (B1 and B2) were identified, with most 2014 EV-D68 outbreak strains belonging to sub-cluster B2b2 (one of the two emerging clusters within sub-clade B2), with two signature substitutions T650A and M700V in BC and DE loops of VP1 gene, respectively. The close homology between WGS of strains from Ontario (n = 2) and USA (n = 21) in the recent EV-D68 outbreak suggests genetic relatedness and also a common source for the outbreak. The time of most recent common ancestor of EV-D68 and the 2014 EV-D68 outbreak strain suggest that the viruses possibly emerged during 1960-1961 and 2012-2013, respectively. We observed lower mean evolutionary rates of global EV-D68 using WGS data than estimated with partial VP1 gene sequences. Based on WGS data, the estimated mean rate of evolution of the EV-D68 B2b cluster was 9.75 × 10-3 substitutions/site/year (95% BCI 4.11 × 10-3 to 16 × 10-3).

Upsurge of Enterovirus D68, the Netherlands, 2016

In June and July 2016, we identified 8 adults and 17 children with respiratory enterovirus D68 infections. Thirteen children required intensive care unit admission because of respiratory insufficiency, and 1 had concomitant acute flaccid myelitis. Phylogenetic analysis showed that all of 20 sequences obtained belong to the recently described clade B3.

Human enterovirus D68 in clinical and sewage samples in Israel

BACKGROUND

Since mid-August 2014, North America experienced a wide outbreak of Enterovirus D68 (EV-D68) associated with severe respiratory illness in children. Several other countries also reported cases of EV-D68 in 2014.

OBJECTIVES

The aim of this study was to determine whether EV-D68 circulated in Israel in 2014, caused severe respiratory illness in children and was the causative agent of Acute Flaccid Paralysis.

STUDY DESIGN

Archived clinical respiratory samples from a cohort of 710 hospitalized pediatric patient's (<10years old) with respiratory illness were screened for clade B specific EV-D68 by real-time PCR. The patients were seen at four medical centers covering the entire country between August and November 2014. We also evaluated 49 patient stool samples from 26 AFP cases during 2014 for presence of EV-D68. In addition, RNA from sewage samples collected throughout Israel during the same study period was also tested for EV-D68. Partial VP1 sequencing was performed on all positive samples.

RESULTS

Of the 710 clinical samples evaluated, 7 (1%) were positive for EV-D68. Two patients were from the central part of Israel, while the rest was from the southern part. The majority of the patients did not have any underlying disease. Not only that, but, none of the 26 suspected AFP cases had EV-D68 nucleic acid in their stool samples. EV-D68 RNA was detected in 9 out of 93 sewage samples, mainly from Southern Israel. Sequence analysis of EV-D68 VP1 gene from both sewage and clinical samples indicated that the Israeli EV-D68 RNA belonged to Clade B which was genetically similar to 2014 circulating European and North American EV-D68 virus.

CONCLUSIONS

EV-D68 circulated in Israel during the 2014 summer-fall season and caused hospitalization of a small percent of the patients with respiratory illness.

Enterovirus D68 in Hospitalized Children: Sequence Variation, Viral Loads and Clinical Outcomes

Background

An outbreak of enterovirus D68 (EV-D68) caused severe respiratory illness in 2014. The disease spectrum of EV-D68 infections in children with underlying medical conditions other than asthma, the role of EV-D68 loads on clinical illness, and the variation of EV-D68 strains within the same institution over time have not been described. We sought to define the association between EV-D68 loads and sequence variation, and the clinical characteristic in hospitalized children at our institution from 2011 to 2014.

Methods

May through November 2014, and August to September 2011 to 2013, a convenience sample of nasopharyngeal specimens from children with rhinovirus (RV)/EV respiratory infections were tested for EV-D68 by RT-PCR. Clinical data were compared between children with RV/EV-non-EV-D68 and EV-D68 infections, and among children with EV-D68 infections categorized as healthy, asthmatics, and chronic medical conditions. EV-D68 loads were analyzed in relation to disease severity parameters and sequence variability characterized over time.

Results

In 2014, 44% (192/438) of samples tested positive for EV-D68 vs. 10% (13/130) in 2011–13 (p<0.0001). PICU admissions (p<0.0001) and non-invasive ventilation (p<0.0001) were more common in children with EV-D68 vs. RV/EV-non-EV-D68 infections. Asthmatic EV-D68+ children, required supplemental oxygen administration (p = 0.03) and PICU admissions (p <0.001) more frequently than healthy children or those with chronic medical conditions; however oxygen duration (p<0.0001), and both PICU and total hospital stay (p<0.01) were greater in children with underlying medical conditions, irrespective of viral burden. By phylogenetic analysis, the 2014 EV-D68 strains clustered into a new sublineage within clade B.

Conclusions

This is one of the largest pediatric cohorts described from the EV-D68 outbreak. Irrespective of viral loads, EV-D68 was associated with high morbidity in children with asthma and co-morbidities. While EV-D68 circulated before 2014, the outbreak isolates clustered differently than those from prior years.

Respiratory infections associated with enterovirus D68 from 2011 to 2015 in Beijing, China

Enterovirus D68 (EV-D68) is an emergent viral pathogen associated with mild to severe respiratory infections. In this study, we describe respiratory infections associated with EV-D68 in Beijing over a 4 year period. Total nucleic acid was extracted from 7,945 clinical specimens collected between January 5, 2011 and July 30, 2015 in Beijing and used for detecting EV-D68 and other enteroviruses by real-time PCR. Overall, 555/7,945 (6.99%) specimens were enterovirus positive: 12/7,945 (0.2%) specimens were EV-D68 positive. Of these patients, 11 were pediatric patients and 1 was a 76-year-old man. The main symptoms for the 12 EV-D68 positive patients were fever (10/12, 83.3%) and cough (6/12, 50%). Ten EV-D68 infection cases were identified in autumn or winter season. The phylogenetic relationships of the 12 EV-D68 viral strains with other strains were analyzed based on the sequences of viral protein 1(VP1). The EV-D68 strains from 2011 to 2013 belonged to groups 1 or 3, while all strains in 2014 were clustered into group 1 together with the strains circulating in the USA. In conclusion, EV-D68 played a role in respiratory infections in Beijing during this period. In addition, the most common EV-D68 strain detected was similar to that circulating in the USA in 2014. J. Med. Virol. 88:1529-1534, 2016. © 2016 Wiley Periodicals, Inc.

Respiratory Presentation of Pediatric Patients in the 2014 Enterovirus D68 Outbreak

Background. In the fall of 2014, a North American outbreak of enterovirus D68 resulted in a significant number of pediatric hospital admissions for respiratory illness throughout North America. This study characterized the clinical presentation and risk factors for a severe clinical course in children admitted to British Columbia Children's Hospital during the 2014 outbreak. Methods. Retrospective chart review of patients with confirmed EV-D68 infection admitted to BCCH with respiratory symptoms in the fall of 2014. Past medical history, clinical presentation, management, and course in hospital was collected and analyzed using descriptive statistics. Comparison was made between those that did and did not require ICU admission to identify risk factors. Results. Thirty-four patients were included (median age 7.5 years). Fifty-three percent of children had a prior history of wheeze, 32% had other preexisting medical comorbidities, and 15% were previously healthy. Ten children (29%) were admitted to the pediatric intensive care unit. The presence of complex medical conditions (excluding wheezing) (P = 0.03) and copathogens was associated with PICU admission (P = 0.02). Conclusions. EV-D68 infection resulted in severe, prolonged presentations of asthma-like illness in the hospitalized pediatric population. Patients with a prior history of wheeze and preexisting medical comorbidities appear to be most severely affected, but the virus can also cause wheezing in previously well children.

Enterovirus D68 and Human Respiratory Infections

Enterovirus D68 (EV-D68) is a member of the species Enterovirus D in the genus Enterovirus of the Picornaviridae family. EV-D68 was first isolated in the United States in 1962 and is primarily an agent of respiratory disease. Infections with EV-D68 have been rarely reported until recently, when reports of EV-D68 associated with respiratory disease increased notably worldwide. An outbreak in 2014 in the United States, for example, involved more than 1,000 cases of severe respiratory disease that occurred across almost all states. Phylogenetic analysis of all EV-D68 sequences indicates that the circulating strains of EV-D68 can be classified into two lineages, lineage 1 and lineage 2. In contrast to the prototype Fermon strain, all circulating strains have deletions in their genomes. Respiratory illness associated with EV-D68 infection ranges from mild illness that just needs outpatient service to severe illness requiring intensive care and mechanical ventilation. To date, there are no specific medicines and vaccines to treat or prevent EV-D68 infection. This review provides a detailed overview about our current understanding of EV-D68-related virology, epidemiology and clinical syndromes, pathogenesis, and laboratory diagnostics.

Update on Human Rhinovirus and Coronavirus Infections

Human rhinovirus (HRV) and coronavirus (HCoV) infections are associated with both upper respiratory tract illness (“the common cold”) and lower respiratory tract illness (pneumonia). New species of HRVs and HCoVs have been diagnosed in the past decade. More sensitive diagnostic tests such as reverse transcription-polymerase chain reaction have expanded our understanding of the role these viruses play in both immunocompetent and immunosuppressed hosts. Recent identification of severe acute respiratory syndrome and Middle East respiratory syndrome viruses causing serious respiratory illnesses has led to renewed efforts for vaccine development. The role these viruses play in patients with chronic lung disease such as asthma makes the search for antiviral agents of increased importance.

Molecular evolution and the global reemergence of enterovirus D68 by genome-wide analysis

Human enterovirus D68 (EV-D68) was first reported in the United States in 1962; thereafter, a few cases were reported from 1970 to 2005, but 2 outbreaks occurred in the Philippines (2008) and the United States (2014). However, little is known regarding the molecular evolution of this globally reemerging virus due to a lack of whole-genome sequences and analyses. Here, all publically available sequences including 147 full and 1248 partial genomes from GenBank were collected and compared at the clade and subclade level; 11 whole genomes isolated in Taiwan (TW) in 2014 were also added to the database. Phylogenetic trees were constructed to identify a new subclade, B3, and represent clade circulations among strains. Nucleotide sequence identities of the VP1 gene were 94% to 95% based on a comparison of subclade B3 to B1 and B2 and 87% to 91% when comparing A, C, and D. The patterns of clade circulation need to be clarified to improve global monitoring of EV-D68, even though this virus showed lower diversity among clades compared with the common enterovirus EV-71. Notably, severe cases isolated from Taiwan and China in 2014 were found in subclade B3. One severe case from Taiwan occurred in a female patient with underlying angioimmunoblastic T-cell lymphoma, from whom a bronchoalveolar lavage specimen was obtained. Although host factors play a key role in disease severity, we cannot exclude the possibility that EV-D68 may trigger clinical symptoms or death. To further investigate the genetic diversity of EV-D68, we reported 34 amino acid (aa) polymorphisms identified by comparing subclade B3 to B1 and B2. Clade D strains had a 1-aa deletion and a 2-aa insertion in the VP1 gene, and 1 of our TW/2014 strains had a shorter deletion in the 5' untranslated region than a previously reported deletion. In summary, a new subclade, genetic indels, and polymorphisms in global strains were discovered elucidating evolutionary and epidemiological trends of EV-D68, and 11 genomes were added to the database. Virus variants may contribute to disease severity and clinical manifestations, and further studies are needed to investigate the associations between genetic diversity and clinical outcomes.

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.

The Emergence of Enterovirus-D68

Enterovirus-D68 (EV-D68) is a unique enterovirus, similar to human rhinoviruses, spread via the respiratory route and primarily causing respiratory disease. Increasing clusters of EV-D68 associated respiratory disease have been reported since 2008, with the largest reported outbreak occurring in North America in 2014. Epidemiologic data and biological plausibility support an association of EV-D68 with the neurologic condition, acute flaccid myelitis. Diagnosis requires EV-D68 specific PCR or viral sequencing of respiratory specimens. Treatment consists of supportive care, as there are no currently available effective vaccines or antiviral therapies. Further research is needed to prepare for future EV-D68 outbreaks of respiratory or neurologic disease.

Enterovirus D68 Infections Associated with Severe Respiratory Illness in Elderly Patients and Emergence of a Novel Clade in Hong Kong

Despite the recent emergence of enterovirus D68 (EV-D68), its clinical impact on adult population is less well defined. To better define the epidemiology of EV-D68, 6,800 nasopharyngeal aspirates (NPAs) from 2010–2014 were subject to EV-D68 detection by RT-PCR and sequencing of 5′UTR and partial VP1. EV-D68 was detected in 30 (0.44%) NPAs from 22 children and 8 adults/elderlies. Sixteen patients (including five elderly) (53%) had pneumonia and 13 (43%) patients were complicated by small airway disease exacerbation. Phylogenetic analysis of VP1, 2C and 3D regions showed four distinct lineages of EV-D68, clade A1, A2, B1 and B3, with adults/elderlies exclusively infected by clade A2. The potentially new clade, B3, has emerged in 2014, while strains closely related to recently emerged B1 strains in the United States were also detected as early as 2011 in Hong Kong. The four lineages possessed distinct aa sequence patterns in BC and DE loops. Amino acid residues 97 and 140, within BC and DE-surface loops of VP1 respectively, were under potential positive selection. EV-D68 infections in Hong Kong usually peak in spring/summer, though with a delayed autumn/winter peak in 2011. This report suggests that EV-D68 may cause severe respiratory illness in adults/elderlies with underlying co-morbidities.

Systematic community- and hospital-based surveillance for enterovirus-D68 in three Canadian provinces, August to December 2014

Respiratory specimens collected from outpatients with influenza-like illness in three Canadian provinces (British Columbia (BC), Alberta and Quebec) participating in a community-based sentinel surveillance network were prospectively screened for enterovirus-D68 (EV-D68) from 1 August to 31 December 2014 and compared to specimens collected from 1 October 2013 to 31 July 2014. Eighteen (1%) of 1,894 specimens were EV-D68-positive: 1/348 (0.3%) collected from October to December 2013 and 11/460 (2.4%) from October to December 2014, an eight-fold increase in detection rates (p=0.01), consistent with epidemic circulation in autumn 2014. The remaining EV-D68 detections were in September 2014 (6/37). Enhanced passive surveillance was also conducted on all inpatient and outpatient EV-D68 cases (n=211) detected at the BC provincial reference laboratory from 28 August to 31 December 2014. Incidence of hospitalisations was 3/100,000 overall and 21, 17, 4 and 1/100,000 among those<5, 5-9, 10-19 and ≥20-years-old with male-to-female ratios>1 among paediatric but not adult cases. Three cases in BC with comorbidity or co-infection died and five exhibited neurological features persisting >9 months. Active surveillance in outpatient and inpatient settings is needed from more areas and additional seasons to better understand EV-D68 epidemiology and potential at-risk groups for severe or unusual manifestations.

Prevalence and phylogenetic characterization of human enterovirus D68 among children with respiratory infection in Hong Kong

This is the first report on the prevalence of human enterovirus D68 (EV-D68) among children with respiratory infection in Hong Kong. Among 1461 respiratory samples taken in 2014, EV-D68 was identified in 24 (1.64%) of them with a unusual seasonal pattern. Phylogenetic analysis indicated that all EV-D68 detected in this study belong to clade B.

Global emergence of enterovirus D68: a systematic review

Since its discovery in California in 1962, reports of enterovirus D68 have been infrequent. Before 2014, infections were confirmed in only 699 people worldwide. In August, 2014, two paediatric hospitals in the USA reported increases in the number of patients with severe respiratory illness, with an over-representation in children with asthma. Shortly after, the authorities recognised a nationwide outbreak, which then spread to Canada, Europe, and Asia. In 2014, more than 2000 cases of enterovirus D68 were reported in 20 countries. Concurrently, clusters of children with acute flaccid paralysis of unknown cause were reported in several US states and in Europe. Enterovirus D68 infection was confirmed in some of the paralysed children, but not all. Complications in patients who were severely neurologically affected resemble those caused by poliomyelitis. In this paper we systematically review reports on enterovirus D68 to estimate its global epidemiology and its ability to cause respiratory infections and neurological damage in children. We extracted data from 70 papers to report on prevalence, symptoms, hospitalisation and mortality, and complications of enterovirus D68, both before and during the large outbreak of 2014. The magnitude and severity of the enterovirus D68 outbreak underscores a need for improved diagnostic work-up of paediatric respiratory illness, not only to prevent unnecessary use of antibiotics, but also to ensure better surveillance of diseases. Existing surveillance systems should be assessed in terms of capacity and ability to detect and report any upsurge of respiratory viruses such as enterovirus D68 in a timely manner, and focus should be paid to development of preventive measures against these emerging enteroviruses that have potential for severe disease.

Genotyping of enteroviruses isolated in Kenya from pediatric patients using partial VP1 region

Enteroviruses (EV) are responsible for a wide range of clinical diseases in humans. Though studied broadly in several regions of the world, the genetic diversity of human enteroviruses (HEV) circulating in the sub-Saharan Africa remains under-documented. In the current study, we molecularly typed 61 HEV strains isolated in Kenya between 2008 and 2011 targeting the 3′-end of the VP1 gene. Viral RNA was extracted from the archived isolates and part of the VP1 gene amplified by RT-PCR, followed by sequence analysis. Twenty-two different EV types were detected. Majority (72.0 %) of these belonged to Enterovirus B species followed by Enterovirus D (21.3 %) and Enterovirus A (6.5 %). The most frequently detected types were Enterovirus-D68 (EV-D68), followed by Coxsackievirus B2 (CV-B2), CV-B1, CV-B4 and CV-B3. Phylogenetic analyses of these viruses revealed that Kenyan CV-B1 isolates were segregated among sequences of global CV-B1 strains. Conversely, the Kenyan CV-B2, CV-B3, CV-B4 and EV-D68 strains generally grouped together with those detected from other countries. Notably, the Kenyan EV-D68 strains largely clustered with sequences of global strains obtained between 2008 and 2010 than those circulating in recent years. Overall, our results indicate that HEV strains belonging to Enterovirus D and Enterovirus B species pre-dominantly circulated and played a significant role in pediatric respiratory infection in Kenya, during the study period. The Kenyan CV-B1 strains were genetically divergent from those circulating in other countries. Phylogenetic clustering of Kenyan EV-D68 strains with sequences of global strains circulating between 2008 and 2010 than those obtained in recent years suggests a high genomic variability associated with the surface protein encoding VP1 gene in these enteroviruses.

3C Protease of Enterovirus D68 Inhibits Cellular Defense Mediated by Interferon Regulatory Factor 7

Human enterovirus 68 (EV-D68) is a member of the EV-D species, which belongs to the EV genus of the Picornaviridae family. Over the past several years, clusters of EV-D68 infections have occurred worldwide. A recent outbreak in the United States is the largest one associated with severe respiratory illness and neurological complication. Although clinical symptoms are recognized, the virus remains poorly understood. Here we report that EV-D68 inhibits innate antiviral immunity by downregulation of interferon regulatory factor 7 (IRF7), an immune factor with a pivotal role in viral pathogenesis. This process depends on 3C(pro), an EV-D68-encoded protease, to mediate IRF7 cleavage. When expressed in host cells, 3C(pro) targets Q167 and Q189 within the constitutive activation domain, resulting in cleavage of IRF7. Accordingly, wild-type IRF7 is fully active. However, IRF7 cleavage abrogated its capacity to activate type I interferon expression and limit replication of EV-D68. Notably, IRF7 cleavage strictly requires the protease activity of 3C(pro). Together, these results suggest that a dynamic interplay between 3C(pro) and IRF7 may determine the outcome of EV-D68 infection.

IMPORTANCE

EV-D68 is a globally emerging pathogen, but the molecular basis of EV-D68 pathogenesis is unclear. Here we report that EV-D68 inhibits innate immune responses by targeting an immune factor, IRF7. This involves the 3C protease encoded by EV-D68, which mediates the cleavage of IRF7. These observations suggest that the 3C(pro)-IRF7 interaction may represent an interface that dictates EV-D68 infection.

Low-level Circulation of Enterovirus D68-Associated Acute Respiratory Infections, Germany, 2014

We used physician sentinel surveillance to identify 25 (7.7%) mild to severe infections with enterovirus D68 (EV-D68) in children and adults among 325 outpatients with acute respiratory infections in Germany during August–October 2014. Results suggested low-level circulation of enterovirus D68 in Germany. Viruses were characterized by sequencing viral protein (VP) 1 and VP4/VP2 genomic regions.

Respiratory Infections by Enterovirus D68 in Outpatients and Inpatients Spanish Children

BACKGROUND

The incidence of enterovirus D68 (EV-D68) and the spectrum of clinical disease in children are not well known in European countries. We have designed a study with the objective of describing the clinical impact of EV-D68 detected in children with respiratory tract infections.

METHODS

As a part of a prospective study to identify the etiology and clinical characteristics of viral respiratory infections in children in Spain, we performed the analysis of the cases of EV infections in all children hospitalized in a secondary hospital in Madrid, during the epidemic respiratory season 2012-2013. A second group of samples was corresponded to infants of the same area, with ambulatory respiratory infection or asymptomatic. Phylogenetic EV-D68 analysis was made using the viral protein 1 gene (VP1). Clinical data of EV-D68 patients were compared with those infected by rhinovirus in the same period and population.

RESULTS

The study population consisted of 720 patients corresponding to 399 episodes of hospitalization for respiratory causes, 44 episodes of ambulatory respiratory infections and 277 children determined as a healthy control group. A total of 22 patients were positive for EVs (3.05%), and 12 of them were specifically typed as EV-D68 (11/443 respiratory infections, 2.5%). The most frequent diagnosis in the 10 hospitalized children with EV-D68 detection was recurrent wheezing. Hypoxia was present in 70% of cases, but admission in the intensive care unit was not required. No neurological signs or symptoms were observed. One patient had an ambulatory mild bronchiolitis and another was asymptomatic. No differences were found with rhinovirus infections except less duration of hypoxia and fever in EV-D68 group.

CONCLUSIONS

EV-D68 infections were detected in 3.05% of respiratory studied samples (2.5% of admissions). The infection was associated with wheezing episodes with hypoxia. No admissions to intensive care unit or neurological symptoms were found.

Full genome analysis of enterovirus D-68 strains circulating in Alberta, Canada

A widespread outbreak of enterovirus (EV)-D68 that started in the summer of 2014 has been reported in the USA and Canada. During the course of this outbreak, EV-D68 was identified as a possible cause of acute, unexplained severe respiratory illness and a temporal association was observed between acute flaccid paralysis with anterior myelitis and EV-D68 detection in the upper respiratory tract. In this study, four nasopharyngeal samples collected from patients in Alberta, Canada with a laboratory diagnosis of EV-D68 were used to determine the near full-length genome sequence directly from the specimens. Phylogenetic analysis was performed to study the genotypes and pathogenesis of the circulating strains. Our results support the contention that mutations in the VP1 gene and other regions of the genome causing altered antigenicity, as well as lack of immunity in the younger population, may be responsible for the increased severe respiratory disease outbreaks of EV-D68 worldwide.

Analysis of Enterovirus 68 Strains from the 2014 North American Outbreak Reveals a New Clade, Indicating Viral Evolution

Enterovirus 68 (EVD68) causes respiratory illness, mostly in children. Despite a reported low-level of transmission, the occurrence of several recent outbreaks worldwide including the 2014 outbreak in North America has raised concerns regarding the pathogenesis and evolution of EVD68. To elucidate the phylogenetic features of EVD68 and possible causes for the 2014 outbreak, 216 EVD68 strain sequences were retrieved from Genbank, including 22 from the 2014 outbreak. Several geographic and genotypic origins were established for these 22 strains, 19 of which were classified as Clade B. Of these 19 strains, 17 exhibited subsequent clustering and variation in protein residues involved in host-receptor interaction and/or viral antigenicity. Approximately 18 inter-clade variations were detected in VP1, which led to the identification of a new Clade D in EVD68 strains. The classification of this new clade was also verified by the re-construction of a Neighbor-Joining tree during the phylogenetic analysis. In addition, our results indicate that members of Clade B containing highly specific alterations in VP1 protein residues were the foremost contributors to the 2014 outbreak in the US. Altered host-receptor interaction and/or host immune recognition may explain the evolution of EVD68 as well as the global emergence and ongoing adaptation of this virus.

Enterovirus D68 Infection

First described in 1962 in children hospitalized for pneumonia and bronchiolitis, the Enterovirus D68 (EV-D68) is an emergent viral pathogen. Since its discovery, during the long period of surveillance up to 2005, EV-D68 was reported only as a cause of sporadic outbreaks. In recent years, many reports from different countries have described an increasing number of patients with respiratory diseases due to EV-D68 associated with relevant clinical severity. In particular, an unexpectedly high number of children have been hospitalized for severe respiratory disease due to EV-D68, requiring intensive care such as intubation and mechanical ventilation. Moreover, EV-D68 has been associated with acute flaccid paralysis and cranial nerve dysfunction in children, which has caused concerns in the community. As no specific antiviral therapy is available, treatment is mainly supportive. Moreover, because no vaccines are available, conventional infection control measures (i.e., standard, for contacts and droplets) in both community and healthcare settings are recommended. However, further studies are required to fully understand the real importance of this virus. Prompt diagnosis and continued surveillance of EV-D68 infections are essential to managing and preventing new outbreaks. Moreover, if the association between EV-D68 and severe diseases will be confirmed, the development of adequate preventive and therapeutic approaches are a priority.

Epidemiology of Enterovirus D68 in Ontario

In August 2014, children's hospitals in Kansas City, Missouri and Chicago, Illinois notified the Centers for Disease Control and Prevention (CDC) about increased numbers of pediatric patients hospitalized with severe respiratory illness (SRI). In response to CDC reports, Public Health Ontario Laboratories (PHOL) launched an investigation of patients being tested for enterovirus D-68 (EV-D68) in Ontario, Canada. The purpose of this investigation was to enhance our understanding of EV-D68 epidemiology and clinical features. Data for this study included specimens submitted for EV-D68 testing at PHOL from September 1, 2014 to October 31, 2014. Comparisons were made between patients who tested positive for the virus (cases) and those testing negative (controls). EV-D68 was identified in 153/907 (16.8%) of patients tested. In the logistic regression model adjusting for age, sex, setting and time to specimen collection, individuals younger than 20 years of age were more likely to be diagnosed with EV-D68 compared to those 20 and over, with peak positivity at ages 5-9 years. Cases were not more likely to be hospitalized than controls. Cases were more likely to be identified in September than October (OR 8.07; 95% CI 5.15 to 12.64). Routine viral culture and multiplex PCR were inadequate methods to identify EV-D68 due to poor sensitivity and inability to differentiate EV-D68 from other enterovirus serotypes or rhinovirus. Testing for EV-D68 in Ontario from July to December, 2014 detected the presence of EV-D68 virus among young children during September-October, 2014, with most cases detected in September. There was no difference in hospitalization status between cases and controls. In order to better understand the epidemiology of this virus, surveillance for EV-D68 should include testing of symptomatic individuals from all treatment settings and patient age groups, with collection and analysis of comprehensive clinical and epidemiological data.

Prevalence and molecular characterizations of enterovirus D68 among children with acute respiratory infection in China between 2012 and 2014

EV-D68 is associated with respiratory tract infections (RTIs). Since its first isolation, EV-D68 has been detected sporadically. However, the US and Canada have experienced outbreaks of EV-D68 infections between August and December 2014. This study aimed to investigate the molecular epidemiology and clinical characteristics of EV-D68 in Chongqing, Southwestern China. From January 2012 to November 2014, 1876 nasopharyngeal aspirate specimens (NPAs) were collected from hospitalized children with RTIs. Among the 1876 NPAs, EV-D68 was detected in 19 samples (1.0%, 19/1876). Of these, 13 samples were detected in September and October 2014 (9.8%, 13/132). Phylogenetic analysis showed that all 13 strains detected in the 2014 Chongqing had high homology with the main strains of the 2014 US outbreak. Among the children with EV-D68 infection, 13 (68%) had a history of recurrent wheezing. A total of 13 children had a discharge diagnosis of asthma. Of these, 11 children were diagnosed with acute asthma exacerbation. EV-D68 was the predominant pathogen that evoked asthma exacerbation in September and October 2014. In conclusion, our results found that a history of recurrent wheezing may be a risk factor for the detection of EV-D68 and viral-induced asthma exacerbation may be a clinical feature of EV-D68 infection.

2014 outbreak of enterovirus D68 in North America

Enterovirus D68 (EV-D68) is an emerging picornavirus which causes severe respiratory disease, predominantly in children. In 2014, the largest and most widespread outbreak of EV-D68 described to date was reported in North America. Hospitals throughout the United States and Canada reported surges in patient volumes and resource utilization from August to October, 2014. In the US a total of 1,153 infections were confirmed in 49 states, although this is an underestimate of the likely millions of cases that occurred but were not tested. EV-D68 was detected in 14 patients who died; the role of the virus in these deaths is unknown. A possible association between EV-D68 and cases of acute flaccid paralysis with spinal cord gray matter lesions, known as acute flaccid myelitis, was observed during the outbreak and is under investigation. The 2014 outbreak of EV-D68 in North America demonstrates the public health importance of this emerging pathogen.

Enterovirus D-68: an emerging cause of infection

The outbreak of Enterovirus D-68 (EV-D68) in the United States in 2014 raised great interest due to it affecting large numbers of people and because patients presented with severe respiratory and/or central nervous system involvement. Many studies have tried to evaluate the biologic and genetic characteristics of this virus, its association with disease development and the possibility of infection prevention and therapy. The main aim of this paper is to discuss what is presently known and what might be expected in the future regarding EV-D68. We highlight that further studies are needed to precisely define the epidemiology and total burden of EV-D68, the real age prevalence, and the factors that may lead to negative outcomes in some patients and not in others. Moreover, if recently reported clinical data are confirmed, specific efficacious prophylactic and therapeutic measures should be urgently developed.