Updates on the molecular epidemiology of Enterovirus D68 after installation of screening test among acute flaccid paralysis patients in Taiwan

Global age-stratified seroprevalence of enterovirus D68: a systematic literature review

Enterovirus D68 (EV-D68), first isolated in 1962, emerged in 2014, causing outbreaks of severe respiratory infections and acute flaccid myelitis. In this systematic review, we have compiled all available literature on age-stratified seroprevalence estimates of EV-D68. Ten studies from six countries were retained, all conducted using microneutralisation assays, despite wide variations in protocols and challenge viruses. The age profiles of seroprevalence were similar across time and regions; seroprevalence increased quickly with age, reaching roughly 100% by the age of 20 years and with no sign of decline throughout adulthood. This suggests continuous or frequent exposure of the populations to the virus, or possible cross-reactivity with other viruses. Studies with two or more cross-sectional surveys reported consistently higher seroprevalence at later timepoints, suggesting a global increase in transmission over time. This systematic review concludes that standardising serological protocols, understanding the contribution of cross-reactivity with other pathogens to the high reported seroprevalence, and quantifying individual exposure to EV-D68 over time are the main research priorities for the future.

Analysis of mild and severe neonatal enterovirus infections in a Chinese neonatal tertiary center: a retrospective case-control study

PURPOSE

To compare the clinical characteristics, virus serotype, and outcome in cases of mild and severe enteroviral infection at a tertiary neonatal intensive care unit in China.

METHODS

A retrospective analysis of cases hospitalized between June and August 2019. Samples (stool or throat swabs) were examined using reverse transcription polymerase chain reaction. Positive cases were divided into two groups: mild infection and severe infection.

RESULTS

A total of 149 cases were assigned to one of two groups: mild infection (n = 104) and severe infection (n = 45). There were no significant differences between the groups in terms of sex, gestational age, birth weight, mode of delivery, and onset within 7 days. Clinical symptoms in both groups mostly resembled sepsis (fever, rash, poor feeding, and lethargy); however, there were significant variations in concomitant symptoms such as hepatitis, thrombocytopenia, encephalitis, coagulopathy, and myocarditis. Severe cases were more likely to have abnormal complete blood counts, biochemical parameters, and cerebrospinal fluid markers. The predominant serotypes implicated in neonatal enterovirus infections were echoviruses and Coxsackievirus B. Invasive ventilation, intravenous immunoglobulin, vasoactive medications, and blood product transfusions were often required, with high mortality rates among severe cases.

CONCLUSION

We found significant differences between mild and severe cases of neonatal enterovirus infection with respect to complications, laboratory findings, and enterovirus serotypes. It is crucial to exercise caution when newborns exhibit symptoms of sepsis, during an enterovirus outbreak. Anemia, thrombocytopenia, abnormal liver function, and coagulation dysfunction should be monitored closely as they could indicate the presence of a severe enteroviral infection.

In vitro and in vivo models for the study of EV-D68 infection

Enterovirus D68 (EV-D68) is one of hundreds of non-polio enteroviruses that typically cause cold-like respiratory illness. The first EV-D68 outbreak in the United States in 2014 aroused widespread concern among the public and health authorities. The infection was found to be associated with increased surveillance of acute flaccid myelitis, a neurological condition that causes limb paralysis in conjunction with spinal cord inflammation. In vitro studies utilising two-dimensional (2D) and three-dimensional (3D) culture systems have been employed to elucidate the pathogenic mechanism of EV-D68. Various animal models have also been developed to investigate viral tropism and distribution, pathogenesis, and immune responses during EV-D68 infection. EV-D68 infections have primarily been investigated in respiratory, intestinal and neural cell lines/tissues, as well as in small-size immunocompetent rodent models that were limited to a young age. Some studies have implemented strategies to overcome the barriers by using immunodeficient mice or virus adaptation. Although the existing models may not fully recapitulate both respiratory and neurological disease observed in human EV-D68 infection, they have been valuable for studying pathogenesis and evaluating potential vaccine or therapeutic candidates. In this review, we summarise the methodologies and findings from each experimental model and discuss their applications and limitations.

Global prevalence and case fatality rate of Enterovirus D68 infections, a systematic review and meta-analysis

A substantial amount of epidemiological data has been reported on Enterovirus D68 (EV-D68) infections after the 2014 outbreak. Our goal was to map the case fatality rate (CFR) and prevalence of current and past EV-D68 infections. We conducted a systematic review (PROSPERO, CRD42021229255) with published articles on EV-68 infections in PubMed, Embase, Web of Science and Global Index Medicus up to January 2021. We determined prevalences using a model random effect. Of the 4,329 articles retrieved from the databases, 89 studies that met the inclusion criteria were from 39 different countries with apparently healthy individuals and patients with acute respiratory infections, acute flaccid myelitis and asthma-related diseases. The CFR estimate revealed occasional deaths (7/1353) related to EV-D68 infections in patients with severe acute respiratory infections. Analyses showed that the combined prevalence of current and past EV-D68 infections was 4% (95% CI = 3.1-5.0) and 66.3% (95% CI = 40.0-88.2), respectively. The highest prevalences were in hospital outbreaks, developed countries, children under 5, after 2014, and in patients with acute flaccid myelitis and asthma-related diseases. The present study shows sporadic deaths linked to severe respiratory EV-D68 infections. The study also highlights a low prevalence of current EV-D68 infections as opposed to the existence of EV-D68 antibodies in almost all participants of the included studies. These findings therefore highlight the need to implement and/or strengthen continuous surveillance of EV-D68 infections in hospitals and in the community for the anticipation of the response to future epidemics.

Infection-Related Myelopathies

Recent years have seen growing attention to inflammatory and infectious disorders of the spinal cord, not only due to the discovery of autoantibody-mediated disorders of the spinal cord [e.g., aquaporin-4 immunoglobulin G (IgG) antibodies and myelin oligodendrocyte glycoprotein IgG antibodies], but also due to the emergence of clusters of infection-related myelopathy, now known as acute flaccid myelitis. We review the spectrum of infection-related myelopathies and outline a nosological classification system based on association with infection. We describe the epidemiology and definitions of myelopathies, with a discussion of clinical presentation and neuroimaging features, and then turn to specific discussion of myelopathies due to direct pathogen invasion and those considered to be post- or parainfectious. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Enhanced Enterovirus D68 Replication in Neuroblastoma Cells Is Associated with a Cell Culture-Adaptive Amino Acid Substitution in VP1

Enterovirus D68 (EV-D68) causes mild to severe respiratory disease and is associated with acute flaccid myelitis since 2014. Currently, the understanding of the ability of EV-D68 to replicate in the central nervous system (CNS), and whether it is associated with a specific clade of EV-D68 viruses or specific viral factors, is lacking. Comparing different EV-D68 clades did not reveal clade-specific phenotypic characteristics. However, we did show that viruses which acquired a cell culture-adapted amino acid substitution in VP1 (E271K) recognized heparan sulfate as an additional receptor. Recognition of heparan sulfate resulted in an increase in attachment, infection, and replication in neuroblastoma cells compared with viruses without this specific amino acid substitution. The ability of EV-D68 viruses to acquire cell culture-adaptive substitutions which have a large effect in experimental settings emphasizes the need to sequence virus stocks.

Since its emergence in the United States in 2014, enterovirus D68 (EV-D68) has been and is associated with severe respiratory diseases and acute flaccid myelitis. Even though EV-D68 has been shown to replicate in different neuronal cells in vitro, it is currently poorly understood which viral factors contribute to the ability to replicate efficiently in cells of the central nervous system and whether this feature is a clade-specific feature. Here, we determined the replication kinetics of clinical EV-D68 isolates from (sub)clades A, B1, B2, B3, and D1 in human neuroblastoma cells (SK-N-SH). Subsequently, we compared sequences to identify viral factors associated with increased viral replication. All clinical isolates replicated in SK-N-SH cells, although there was a large difference in efficiency. Efficient replication of clinical isolates was associated with an amino acid substitution at position 271 of VP1 (E271K), which was acquired during virus propagation in vitro. Recognition of heparan sulfate in addition to sialic acids was associated with increased attachment, infection, and replication. Removal of heparan sulfate resulted in a decrease in attachment, internalization, and replication of viruses with E271K. Taken together, our study suggests that the replication kinetics of EV-D68 isolates in SK-N-SH cells is not a clade-specific feature. However, recognition of heparan sulfate as an additional receptor had a large effect on phenotypic characteristics in vitro. These observations emphasize the need to compare sequences from virus stocks with clinical isolates in order to retrieve phenotypic characteristics from original virus isolates.

IMPORTANCE Enterovirus D68 (EV-D68) causes mild to severe respiratory disease and is associated with acute flaccid myelitis since 2014. Currently, the understanding of the ability of EV-D68 to replicate in the central nervous system (CNS), and whether it is associated with a specific clade of EV-D68 viruses or specific viral factors, is lacking. Comparing different EV-D68 clades did not reveal clade-specific phenotypic characteristics. However, we did show that viruses which acquired a cell culture-adapted amino acid substitution in VP1 (E271K) recognized heparan sulfate as an additional receptor. Recognition of heparan sulfate resulted in an increase in attachment, infection, and replication in neuroblastoma cells compared with viruses without this specific amino acid substitution. The ability of EV-D68 viruses to acquire cell culture-adaptive substitutions which have a large effect in experimental settings emphasizes the need to sequence virus stocks.

Enterovirus D68-associated respiratory infection in southern Brazil, 2018 - A population-based laboratory surveillance

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Patients with SARI or ILI notified during epidemiological surveillance are investigated to detect respiratory virus.

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Enteroviruses were detected in 69/6535 (1%), being 39/69 (56.5 %) of SARI, and 30/69 (43.5 %) of ILI cases.

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EV-D68 was detected in the 36 samples previously identified as EV/RV co-detection.

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This finding settles the sustained circulation of EV-D68 in southern Brazil.

Enterovirus D68 (EV-D68) strain was confirmed in 36/69−52.2% of enterovirus-positive samples collected through surveillance networks for severe acute respiratory infections (SARI) and influenza-like illness (ILI) in southern Brazil in 2018. This finding settles the sustained circulation of EV-D68 in southern Brazil.

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.

Enterovirus D68 seroepidemiology in Taiwan, a cross sectional study from 2017

BACKGROUND

Enterovirus D68 (EV-D68) was discovered in 1962 and has unique characteristics compared to the characteristics of other enteroviruses. There were few documented cases before the epidemic in the United States in 2014. The Taiwan Centers for Diseases Control also confirmed that EV-D68 has been endemic, and some cases of acute flaccid myelitis were reported in Taiwan. To understand the current EV-D68 serostatus, we performed an EV-D68 seroepidemiology study in Taiwan in 2017.

METHODS

After informed consent was obtained, we enrolled preschool children, 6- to 15-year-old students and 16- to 49-year-old people. The participants underwent a questionnaire investigation and blood sampling to measure the EV-D68 neutralization antibody.

RESULTS

In total, 920 subjects were enrolled from the northern, central, southern and eastern parts of Taiwan with a male-to-female ratio of 1.03. The EV-D68 seropositive rate was 32% (26/82) in infants, 18% (27/153) in 1-year-old children, 43% (36/83) in 2-year-old children, 60% (94/156) in 3- to 5-year-old children, 89% (108/122) in 6- to 11-year-old primary school students, 98% (118/121) in 12- to 15-year-old high school students, 100% (122/122) in 16- to 49-year-old women and 100% (81/81) in 16- to 49-year-old males in 2017. Among preschool children, EV-D68 seropositivity was related to age (p for trend <0.0001), size of household ≧4 members (p = 0.037) and kindergarten attendance (p = 0.027). The seropositive rate varied among different geographic regions.

CONCLUSION

EV-D68 infection was prevalent, and its seropositive rates increased with age, larger household size and kindergarten attendance among preschool children.

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.

Enteroviral infection in neonates

Enteroviruses generally cause mild and self-limited diseases, but they have been found to affect neonates much differently, and often more severely than older children. Clinical manifestations are difficult to differentiate from those of bacterial sepsis, such as fever, poor feeding, lethargy, respiratory distress and cardiovascular collapse. Severe life threatening complications, including hepatic necrosis with coagulopathy, meningoencephalitis and myocarditis, usually present during the first week of life. Factors affecting severity and outcome include virus serotype, mode of transmission, and presence or absence of passively acquired, serotype-specific maternal antibodies. Echoviruses and coxsackievirus B viruses are most common serotypes associated with the neonatal sepsis. An awareness of the clinical syndromes, recognition of the risk factors and monitoring parameters associated with severe cases and use of rapid reverse-transcriptase polymerase chain reaction test for viral load may help physicians in diagnosing severe cases in a timely manner. Prompt aggressive treatment including early intravenous immunoglobulin treatment may help in reducing morbidity and mortality. Enterovirus infections in neonates are common and should be routinely considered in the differential diagnosis of febrile neonates, particularly during enterovirus season. This article provides an overview of what is known about non-polio enteroviruses in neonates including epidemiology, transmission, clinical presentation, diagnosis, and treatment.

Enterovirus D68 Subclade B3 Circulation in Senegal, 2016: Detection from Influenza-like Illness and Acute Flaccid Paralysis Surveillance

Following the 2014 outbreak, active surveillance of the EV-D68 has been implemented in many countries worldwide. Despite subsequent EV-D68 outbreaks (2014 and 2016) reported in many areas, EV-D68 circulation remains largely unexplored in Africa except in Senegal, where low levels of EV-D68 circulation were first noted during the 2014 outbreak. Here we investigate subsequent epidemiology of EV-D68 in Senegal from June to September 2016 by screening respiratory specimens from ILI and stool from AFP surveillance. EV-D68 was detected in 7.4% (44/596) of patients; 40 with ILI and 4 with AFP. EV-D68 detection was significantly more common in children under 5 years (56.8%, p = 0.016). All EV-D68 strains detected belonged to the newly defined subclade B3. This study provides the first evidence of EV-D68 B3 subclade circulation in Africa from patients with ILI and AFP during a 2016 outbreak in Senegal. Enhanced surveillance of EV-D68 is needed to better understand the epidemiology of EV-D68 in Africa.

Case report: painful exanthems caused by enterovirus D68 in an adolescent

RATIONALE

Unlike other enteroviruses which can cause herpangina or hand-foot-and-mouth disease, enterovirus D68 (EV-D68) has usually been linked to respiratory and neurological problems in young children. Skin manifestations had rarely been described in current literatures.

PATIENT CONCERNS

We report a 17-year-old girl with fever and painful skin rash over legs and soles for 9 days. Pitting edema was also noted below the knees. There was no respiratory tract or neurological symptoms in this patient.

DIAGNOSES

EV-D68 was detected from a throat swab by RT-PCR and confirmed to be subclade B3 by sequencing.

INTERVENTIONS

Supportive management.

OUTCOMES

The patient was afebrile after 9 days and got full recovery on the 23rd day at outpatient follow-up.

LESSONS

To the best of our knowledge, this is the first report of EV-D68 infection with skin manifestations, clinical images, and detailed clinical course. Our findings in this particular case extend the understanding of the disease spectrum.

A case report of the enterovirus-D68 associated severe acute respiratory illness in a pediatric case from India

Since, early 2000s, there have been several clusters of enterovirus-D68 (EV D68) associated respiratory illness reported from various countries. Recent largest and most wide-spread outbreak of EV-D68 associated severe acute respiratory illness (SARI) occurred in North America. Present report describes a case of EV-D68 associated severe acute respiratory illness from India with a whole genome sequence. The case was identified through retrospective analysis of Influenza SARI surveillance sample collected during September 2017 using Next Generation sequencing. EV D68 positive child aged two years and presented with asthma like symptoms for which he was admitted to ICU. The child tested negative for Influenza, RSV, Rhinovirus, PIV, hMPV and adenovirus, on real time RT-PCR. And on NGS full EV D68 genome was retrieved belonging to sub-clade B3. In ICU, child received anti-bacterial and anti-viral therapy. The child recovered with-out any sequelae and was discharged one week later. Present report highlights the importance of studying this emergent virus EV-D68 through prospective studies to understand the burden and epidemiological pattern in the country and its implications.

Intra- and interpatient evolution of enterovirus D68 analyzed by whole-genome deep sequencing

Worldwide outbreaks of enterovirus D68 (EV-D68) in 2014 and 2016 have caused serious respiratory and neurological disease. To investigate diversity, spread, and evolution of EV-D68 we performed near full-length deep sequencing in fifty-four samples obtained in Sweden during the 2014 and 2016 outbreaks. In most samples, intrapatient variability was low and dominated by rare synonymous variants, but three patients showed evidence of dual infections with distinct EV-D68 variants from the same subclade. Interpatient evolution showed a very strong temporal signal, with an evolutionary rate of 0.0039 ± 0.0001 substitutions per site and year. Phylogenetic trees reconstructed from the sequences suggest that EV-D68 was introduced into Stockholm several times during the 2016 outbreak. Putative neutralization targets in the BC and DE loops of the VP1 protein were slightly more diverse within-host and tended to undergo more frequent substitution than other genomic regions. However, evolution in these loops did not appear to have been driven the emergence of the 2016 B3-subclade directly from the 2014 B1-subclade. Instead, the most recent ancestor of both clades was dated to 2009. The study provides a comprehensive description of the intra- and interpatient evolution of EV-D68, including the first report of intrapatient diversity and dual infections. The new data along with publicly available EV-D68 sequences are included in an interactive phylodynamic analysis on nextstrain.org/enterovirus/d68 to facilitate timely EV-D68 tracking in the future.

Contemporary Circulating Enterovirus D68 Strains Have Acquired the Capacity for Viral Entry and Replication in Human Neuronal Cells

Since the EV-D68 outbreak during the summer of 2014, evidence of a causal link to a type of limb paralysis (AFM) has been mounting. In this article, we describe a neuronal cell culture model (SH-SY5Y cells) in which a subset of contemporary 2014 outbreak strains of EV-D68 show infectivity in neuronal cells, or neurotropism. We confirmed the difference in neurotropism in vitro using primary human neuron cell cultures and in vivo with a mouse paralysis model. Using the SH-SY5Y cell model, we determined that a barrier to viral entry is at least partly responsible for neurotropism. SH-SY5Y cells may be useful in determining if specific EV-D68 genetic determinants are associated with neuropathogenesis, and replication in this cell line could be used as rapid screening tool for identification of neurotropic EV-D68 strains. This may assist with better understanding of pathogenesis and epidemiology and with the development of potential therapies.

Enterovirus D68 (EV-D68) has historically been associated with respiratory illnesses. However, in the summers of 2014 and 2016, EV-D68 outbreaks coincided with a spike in polio-like acute flaccid myelitis/paralysis (AFM/AFP) cases. This raised concerns that EV-D68 could be the causative agent of AFM during these recent outbreaks. To assess the potential neurotropism of EV-D68, we utilized the neuroblastoma-derived neuronal cell line SH-SY5Y as a cell culture model to determine if differential infection is observed for different EV-D68 strains. In contrast to HeLa and A549 cells, which support viral infection of all EV-D68 strains tested, SH-SY5Y cells only supported infection by a subset of contemporary EV-D68 strains, including isolates from the 2014 outbreak. Viral replication and infectivity in SH-SY5Y were assessed using multiple assays: virus production, cytopathic effects, cellular ATP release, and VP1 capsid protein production. Similar differential neurotropism was also observed in differentiated SH-SY5Y cells, primary human neuron cultures, and a mouse paralysis model. Using the SH-SY5Y cell culture model, we determined that barriers to viral binding and entry were at least partly responsible for the differential infectivity phenotype. Transfection of genomic RNA into SH-SY5Y generated virions for all EV-D68 isolates, but only a single round of replication was observed from strains that could not directly infect SH-SY5Y. In addition to supporting virus replication and other functional studies, this cell culture model may help identify the signatures of virulence to confirm epidemiological associations between EV-D68 strains and AFM and allow for the rapid identification and characterization of emerging neurotropic strains.