Enterovirus virus-like-particle and inactivated poliovirus vaccines do not elicit substantive cross-reactive antibody responses

Human enteroviruses are the most common human pathogen with over 300 distinct genotypes. Previous work with poliovirus has suggested that it is possible to generate antibody responses in humans and animals that can recognize members of multiple enterovirus species. However, cross protective immunity across multiple enteroviruses is not observed epidemiologically in humans. Here we investigated whether immunization of mice or baboons with inactivated poliovirus or enterovirus virus-like-particles (VLPs) vaccines generates antibody responses that can recognize enterovirus D68 or A71. We found that mice only generated antibodies specific for the antigen they were immunized with, and repeated immunization failed to generate cross-reactive antibody responses as measured by both ELISA and neutralization assay. Immunization of baboons with IPV failed to generate neutralizing antibody responses against enterovirus D68 or A71. These results suggest that a multivalent approach to enterovirus vaccination is necessary to protect against enterovirus disease in vulnerable populations.

Surveillance for Acute Flaccid Myelitis - United States, 2018-2022

Acute flaccid myelitis (AFM) is a serious neurologic condition primarily affecting children; AFM can cause acute respiratory failure and permanent paralysis. AFM is a rare but known complication of various viral infections, particularly those of enteroviruses (EVs). Increases in AFM cases during 2014, 2016, and 2018 were associated with EV-D68 infection. This report examines trends in confirmed AFM cases during 2018-2022 and patients' clinical and laboratory characteristics. The number of AFM cases was low during 2019-2022 (28-47 cases per year); the number of cases remained low in 2022 despite evidence of increased EV-D68 circulation in the United States. Compared with cases during the most recent peak year (2018), fewer cases during 2019-2021 had upper limb involvement, prodromal respiratory or febrile illness, or cerebrospinal fluid pleocytosis, and more were associated with lower limb involvement. It is unclear why EV-D68 circulation in 2022 was not associated with an increase in AFM cases or when the next increase in AFM cases will occur. Nonetheless, clinicians should continue to suspect AFM in any child with acute flaccid limb weakness, especially those with a recent respiratory or febrile illness.

Non-Polio Enteroviruses Isolated by Acute Flaccid Paralysis Surveillance Laboratories in the Russian Federation in 1998-2021: Distinct Epidemiological Features of Types

More than 100 types of non-polio enteroviruses (NPEVs) are ubiquitous in the human population and cause a variety of symptoms ranging from very mild to meningitis and acute flaccid paralysis (AFP). Much of the information regarding diverse pathogenic properties of NPEVs comes from the surveillance of poliovirus, which also yields NPEV. The analysis of 265 NPEV isolations from 10,433 AFP cases over 24 years of surveillance and more than 2500 NPEV findings in patients without severe neurological lesions suggests that types EV-A71, E13, and E25 were significantly associated with AFP. EV-A71 was also significantly more common among AFP patients who had fever at the onset and residual paralysis compared to all AFP cases. In addition, a significant disparity was noticed between types that were common in humans (CV-A2, CVA9, EV-A71, E9, and E30) or in sewage (CVA7, E3, E7, E11, E12, and E19). Therefore, there is significant evidence of non-polio viruses being implicated in severe neurological lesions, but further multicenter studies using uniform methodology are needed for a definitive conclusion.

Neurotropic enteroviruses (Picornaviridae: Enterovirus): predominant types, basis of neurovirulence

Enteroviruses are one of the most common causative agents of infectious diseases of the central nervous system. They are characterized by genetic variability, the ability to infect a wide range of cells, including brain microglial cells and astrocytes, and persist in the central nervous system tissue, causing delayed and chronic diseases. The review presents data on the basis of neurovirulence of non-polio enteroviruses and the most common pathogens causing enteroviral neuroinfections.

Diagnostic Accuracy of Manual Muscle Testing to Identify Nerve Transfer Candidates in Children with Acute Flaccid Myelitis

BACKGROUND

Manual muscle testing is a mainstay of strength assessment despite not having been compared with intraoperative electrical stimulation of peripheral nerves.

METHODS

Intraoperative electrical stimulation served as the reference standard in evaluating predictive accuracy of the Active Movement Scale (AMS) and the Medical Research Council (MRC) scale. Retrospective consecutive sampling of all patients with AFM who underwent exploration or nerve transfer at a pediatric multidisciplinary brachial plexus and peripheral nerve center from March of 2016 to July of 2020 were included. The nonparametric area under the curve (AUC) was calculated. Optimal cutoff score (Youden J ) and diagnostic accuracy values were reported. The AMS and MRC scale were directly compared for predictive superiority.

RESULTS

A total of 181 upper extremity nerves (73 donor nerve candidates and 108 recipient nerve candidates) were tested intraoperatively from 40 children (mean age ± SD, 7.9 ± 4.9 years). The scales performed similarly ( P = 0.953) in classifying suitable donor nerves with satisfactory accuracy (AUC AMS , 71.5%; AUC MRC , 70.7%; optimal cutoff, AMS >5 and MRC >2). The scales performed similarly ( P = 0.688) in classifying suitable recipient nerves with good accuracy (AUC AMS , 92.1%; AUC MRC :, 94.9%; optimal cutoff, AMS ≤3 and MRC ≤1).

CONCLUSIONS

Manual muscle testing is an accurate, noninvasive means of identifying donor and recipient nerves for transfer in children with acute flaccid myelitis. The utility of these results is in minimizing unexpected findings in the operating room and aiding in the development of contingency plans. Further research may extend these findings to test the validity of manual muscle testing as an outcome measure of the success of nerve transfer.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Diagnostic, I.

EV-D68 virus-like particle vaccines elicit cross-clade neutralizing antibodies that inhibit infection and block dissemination

Enterovirus D68 (EV-D68) causes severe respiratory illness in children and can result in a debilitating paralytic disease known as acute flaccid myelitis. No treatment or vaccine for EV-D68 infection is available. Here, we demonstrate that virus-like particle (VLP) vaccines elicit a protective neutralizing antibody against homologous and heterologous EV-D68 subclades. VLP based on a B1 subclade 2014 outbreak strain elicited comparable B1 EV-D68 neutralizing activity as an inactivated viral particle vaccine in mice. Both immunogens elicited weaker cross-neutralization against heterologous viruses. A B3 VLP vaccine elicited more robust neutralization of B3 subclade viruses with improved cross-neutralization. A balanced CD4⁺ T helper response was achieved using a carbomer-based adjuvant, Adjuplex. Nonhuman primates immunized with this B3 VLP Adjuplex formulation generated robust neutralizing antibodies against homologous and heterologous subclade viruses. Our results suggest that both vaccine strain and adjuvant selection are critical elements for improving the breadth of protective immunity against EV-D68.

Challenges in the Clinical Recognition of Acute Flaccid Myelitis and its Implications

OBJECTIVES

To explore the challenges in diagnosing acute flaccid myelitis (AFM) and evaluate clinical features and treatment paradigms associated with under recognition.

STUDY DESIGN

This was a retrospective multicenter study of pediatric patients (≤18 years) who were diagnosed with AFM from 2014 to 2018 using the Centers for Disease Control and Prevention's case definition.

RESULTS

In 72% of the cases (126 of 175), AFM was not considered in the initial differential diagnosis (n = 108; 61.7%) and/or the patient was not referred for acute care (n = 90; 51.4%) at the initial clinical encounter, and this did not improve over time. Although many features of the presentation were similar in those initially diagnosed with AFM and those who were not; preceding illness, constipation, and reflexes differed significantly between the 2 groups. Patients with a non-AFM initial diagnosis more often required ventilatory support (26.2% vs 12.2%; OR, 0.4; 95% CI, 0.2-1.0; P = .05). These patients received immunomodulatory treatment later (3 days vs 2 days after neurologic symptom onset; 95% CI, -2 to 0; P = .05), particularly intravenous immunoglobulin (5 days vs 2 days; 95% CI, -4 to -2; P < .001).

CONCLUSIONS

Delayed recognition of AFM is concerning because of the risk for respiratory decompensation and need for intensive care monitoring. A non-AFM initial diagnosis was associated with delayed treatment that could have a clinical impact, particularly as new treatment options emerge.

Six- and 12-month functional outcomes among patients with confirmed acute flaccid myelitis (AFM) with onset in 2018, United States

PURPOSE

Acute flaccid myelitis (AFM), an uncommon but serious neurologic condition, primarily affects children, and can progress quickly to paralysis and respiratory failure. Data on long-term outcomes of patients with AFM are limited. This study reports on functional status through 12 months for AFM patients who became ill in 2018 in the United States.

METHODS

Health departments collected information on outcomes at 6 and 12 months after onset of AFM using a standardized form that asked patients or their parents/guardians about functional status. Analyses were restricted to confirmed cases.

RESULTS

Of the 238 confirmed AFM cases reported to CDC in 2018, 90 (38%) had assessments at 6 months, 82 (34%) at 12 months, and 49 (21%) at both 6 and 12 months. Among the 49 patients with data at both time points, the proportion of patients reporting significant or severe impairment at 6 months ranged from 2% to 59% depending on the outcome. Although proportions decreased by 12 months and ranged from 2% to 51%, most patients had some impairment at 12 months. No deaths were reported.

CONCLUSION

Six- and 12-month outcomes in patients with onset of AFM in 2018 span a wide range of functionality, particularly of upper and lower extremities. Importantly, improvement appears to occur over time in some patients.

Acute flaccid myelitis a review of the literature

Acute flaccid myelitis (AFM) is a rare neurological disorder that first rose to national attention in 2014. This neurological disorder has a biennial presentation with every other even year being a peak year. Most patients present in childhood 5 days after a prodromal infection. Patients usually present with muscle weakness and hypo or areflexia in the summer or fall months. Clinical outcomes are variable however most patients do not improve. Currently there are no definitive prognostic factors or etiologies found. However, it is thought that enterovirus-D68 (EV-D68) could be a potential component in the pathobiology of AFM. Treatment options are limited with variable options and no consensus. Supportive therapy has been shown to be the most effective thus far. With our review of the literature, we highlight the recent growing evidence of a possible relationship between EV-D68 and AFM. Additionally, we identify the knowledge gaps in AFM with treatment and prognostic factors.

Animal Models of Enterovirus D68 Infection and Disease

Human enterovirus D68 (EV-D68) is a globally reemerging respiratory pathogen that is associated with the development of acute flaccid myelitis (AFM) in children. Currently, there are no approved vaccines or treatments for EV-D68 infection, and there is a paucity of data related to the virus and host-specific factors that predict disease severity and progression to the neurologic syndrome. EV-D68 infection of various animal models has served as an important platform for characterization and comparison of disease pathogenesis between historic and contemporary isolates. Still, there are significant gaps in our knowledge of EV-D68 pathogenesis that constrain the development and evaluation of targeted vaccines and antiviral therapies. Continued refinement and characterization of animal models that faithfully reproduce key elements of EV-D68 infection and disease is essential for ensuring public health preparedness for future EV-D68 outbreaks.

Does acute flaccid myelitis cause respiratory failure in children?

INTRODUCTION

Acute flaccid myelitis (AFM) is a rare disease that affects spinal cord gray matter, results in acute flaccid weakness of one or more limbs and predominantly involves the cervical spinal cord, which places patients at higher risk for respiratory failure. Our study aims to describe respiratory failure in pediatric AFM patients with emphasis on the need for assisted ventilation and respiratory nerve involvement from an acute and long-term perspective.

MATERIALS AND METHODS

We reviewed the medical records of patients diagnosed with AFM seen in a multidisciplinary clinic for persistent limb weakness between 2016 and 2020.

RESULTS

We studied 54 patients, 35% were female. The median age of patients at illness onset was 5 years (range 7 months-19 years). The median age of patients at the time of study was 8.5 years (range 2-20 years). Eleven patients (20%) required assisted ventilation for acute respiratory failure. Of those that experienced acute respiratory failure, 81% developed chronic respiratory failure. Fifty-six percent of patients with chronic respiratory failure were able to wean off assisted ventilation by 1 year. All patients that experienced unilateral diaphragm impairment with AFM onset experienced acute and chronic respiratory failure.

DISCUSSION

Many patients with AFM may experience respiratory compromise and develop chronic respiratory failure. However, most of these patients can be weaned off ventilatory support by 1 year from illness onset. Most children with unilateral diaphragm impairment can sustain adequate ventilation without the need for long-term ventilatory support.

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.

Enterovirus D68 (EV-D68) infections represent a global public health concern. EV-D68 are detected in apparently healthy subjects and patients with acute respiratory illnesses, acute flaccid myelitis, and asthma-related illnesses. Enterovirus D68 was first described in 1962 and exhibited sporadic circulation until August 2014 when outbreaks of EV-D68 infections were reported in the USA and Canada mainly in children with acute flaccid myelitis and severe acute respiratory disease. We systematically reviewed the literature on EV-D68 infections globally in the present study to determine the case fatality rate and prevalence of current and past infections. Our results show sporadic deaths in patients with severe acute respiratory EV-D68 infections. Our data also show a low prevalence of EV-D68 in current infections unlike the presence of EV-D68 antibodies (past infections) in almost all individuals of all ages. EV-D68 infections were more prevalent in hospital outbreaks, industrialized countries, children < 5 years, and patients with acute flaccid myelitis and asthma-related diseases. These data highlight the need to strengthen the surveillance of EV-D68 infections.

National Surveillance for Acute Flaccid Myelitis - United States, 2018-2020

Acute flaccid myelitis (AFM), a recognized complication of certain viral infections, is a serious neurologic condition that predominantly affects previously healthy children and can progress rapidly, leading to respiratory insufficiency and permanent paralysis. After national AFM surveillance began in 2014, peaks in AFM cases were observed in the United States in 2014, 2016, and 2018 (1). On the basis of this biennial pattern, an increase in AFM was anticipated in 2020. To describe the epidemiology of confirmed AFM cases since 2018, demographic, clinical, and laboratory information collected as part of national AFM surveillance was reviewed. In 2018, a total of 238 confirmed AFM cases were reported to CDC, compared with 47 cases in 2019 and 32 in 2020. Enterovirus D68 (EV-D68) was detected in specimens from 37 cases reported in 2018, one case in 2019 and none in 2020. Compared with 2018, cases reported during 2019-2020 occurred in older children and were less frequently associated with upper limb involvement, febrile or respiratory prodromal illness, or cerebrospinal fluid (CSF) pleocytosis. These findings suggest that the etiologies of AFM in 2019 and 2020 differed from those in 2018. The absence of an increase in cases in 2020 reflects a deviation from the previously observed biennial pattern, and it is unclear when the next increase in AFM should be expected. Clinicians should continue to maintain vigilance and suspect AFM in any child with acute flaccid limb weakness, particularly in the setting of recent febrile or respiratory illness.

Pediatric Spinal Cord Diseases

Spinal cord diseases in pediatric patients are highly variable in terms of presentation, pathology, and prognosis. Not only do they differ with respect to each other but so too with their adult equivalents. Some of the most common diseases are autoimmune (ie, multiple sclerosis, acute disseminated encephalomyelitis, and acute transverse myelitis), congenital (ie, dysraphism with spina bifida, split cord malformation, and tethered cord syndrome), tumor (ie, juvenile pilocytic astrocytoma, ependymoma, and hem-angioblastoma), and vascular (ie, cavernous malformations, arteriovenous malformations, and dural arteriovenous fistulas) in nature. These each require their own niche treatment paradigm and prognosis. Furthermore, presentation of different spinal cord diseases in children can be difficult to discern without epidemiologic and imaging data. Interpretation of these data is crucial to facilitating a timely and accurate diagnosis. Correspondingly, the aim of this review was to highlight the most pertinent features of the most common spinal cord diseases in the pediatric population.

Unraveling the Mysteries of Acute Flaccid Myelitis: Scientific Opportunities and Priorities for Future Research

Since 2014, cases of acute flaccid myelitis (AFM) have been reported in the United States in increasing numbers biennially, occurring in the late summer and early fall. Although there is unlikely to be a single causative agent of this syndrome, non-polio enteroviruses, including enterovirus D-68 (EV-D68), have had epidemiological and laboratory associations with AFM. Much remains to be known about AFM and AFM-associated enteroviruses, including disease pathogenesis and the best strategies for development of therapeutics or preventive modalities including vaccines. To catalyze research that addresses these scientific and clinical gaps, the National Institute of Allergy and Infectious Diseases convened a workshop entitled "AFM Preparedness: Addressing EV-D68 and Other AFM-Associated Enteroviruses" on 19-20 February 2020.

Acute Myelopathy: Vascular and Infectious Diseases

Vascular and infectious causes are rare but important causes of spinal cord injury. High suspicion for these processes is necessary, as symptoms may progress over hours to days, resulting in delayed presentation and diagnosis and worse outcomes. History and clinical examination findings can assist with localization of the affected vascular territory and spinal level, which will assist with focusing spinal imaging. Open and/or endovascular surgical management depends on the associated vascular abnormality. Infectious myelopathy treatment consists of targeted antimicrobial therapy when possible, infectious source control, and again, close monitoring for systemic complications.

Acute Flaccid Myelitis

Acute flaccid myelitis (AFM) is an incompletely understood neurologic disorder occurring in epidemic fashion causing weakness ranging from mild paresis to devastating paralysis in children and some adults. This article reviews the case definition of AFM as well as its epidemiology and association with enteroviral infection. The clinical presentation, diagnostic investigation with particular attention to electrodiagnostics, acute management, and surgical options are described. Clinical outcomes and considerations for acute and long-term rehabilitation management are discussed extensively based on review of current literature, highlighting avenues for further study.

Functional and structural characterization of a two-MAb cocktail for delayed treatment of enterovirus D68 infections

Enterovirus D68 (EV-D68) is an emerging pathogen associated with respiratory diseases and/or acute flaccid myelitis. Here, two MAbs, 2H12 and 8F12, raised against EV-D68 virus-like particle (VLP), show distinct preference in binding VLP and virion and in neutralizing different EV-D68 strains. A combination of 2H12 and 8F12 exhibits balanced and potent neutralization effects and confers broader protection in mice than single MAbs when given at onset of symptoms. Cryo-EM structures of EV-D68 virion complexed with 2H12 or 8F12 show that both antibodies bind to the canyon region of the virion, creating steric hindrance for sialic acid receptor binding. Additionally, 2H12 binding can impair virion integrity and trigger premature viral uncoating. We also capture an uncoating intermediate induced by 2H12 binding, not previously described for picornaviruses. Our study elucidates the structural basis and neutralizing mechanisms of the 2H12 and 8F12 MAbs and supports further development of the 2H12/8F12 cocktail as a broad-spectrum therapeutic agent against EV-D68 infections in humans.

Acute Flaccid Myelitis: A Multidisciplinary Protocol to Optimize Diagnosis and Evaluation

Acute flaccid myelitis is an emerging neurologic disease, first described in 2014 and predominantly affecting young children. Acute flaccid myelitis cases tend to spike every 2 years, in the late summer to fall, and the next peak is expected in 2020. The diagnosis of acute flaccid myelitis is often delayed, leading to suboptimal evaluation, including incomplete laboratory assessment. Acute and chronic morbidity are high, and a standardized, multidisciplinary approach to evaluation and treatment is essential to optimizing outcomes. In a review of acute flaccid myelitis patients treated in 2018 at our institution, we noted considerable variability in days to presentation, evaluation, and treatment. In response, the authors developed a protocol for the evaluation and management of pediatric patients suspected of having acute flaccid myelitis. The protocol was developed using local experience/case review, expert consensus, and the relevant literature. The protocol spans the spectrum of care, from initial evaluation in a primary care or emergency setting, to acute hospital management and evaluation and long-term inpatient and rehabilitation settings. The purpose of this report is both to share the findings from our 2018 case review and to disseminate our acute flaccid myelitis protocol. Our hope is that publication of our protocol will both inform the development of a standardized approach to acute flaccid myelitis and to encourage other centers to form a multidisciplinary acute flaccid myelitis team to provide expert care throughout the disease process, from presentation to recovery.

Epidemiological dynamics of enterovirus D68 in the United States and implications for acute flaccid myelitis

Acute flaccid myelitis (AFM) recently emerged in the United States as a rare but serious neurological condition since 2012. Enterovirus D68 (EV-D68) is thought to be a main causative agent, but limited surveillance of EV-D68 in the United States has hampered the ability to assess their causal relationship. Using surveillance data from the BioFire Syndromic Trends epidemiology network in the United States from January 2014 to September 2019, we characterized the epidemiological dynamics of EV-D68 and found latitudinal gradient in the mean timing of EV-D68 cases, which are likely climate driven. We also demonstrated a strong spatiotemporal association of EV-D68 with AFM. Mathematical modeling suggested that the recent dominant biennial cycles of EV-D68 dynamics may not be stable. Nonetheless, we predicted that a major EV-D68 outbreak, and hence an AFM outbreak, would have still been possible in 2020 under normal epidemiological conditions. Nonpharmaceutical intervention efforts due to the ongoing COVID-19 pandemic are likely to have reduced the sizes of EV-D68 and AFM outbreaks in 2020, illustrating the broader epidemiological impact of the pandemic.

Characteristics of Patients with Acute Flaccid Myelitis, United States, 2015-2018

Differences between years with and without increased activity suggest differences in viral etiologies.

Observed peaks of acute flaccid myelitis (AFM) cases have occurred biennially since 2014 in the United States. We aimed to determine if AFM etiology differed between peak and nonpeak years, considering that clinical features of AFM differ by virus etiology. We compared clinical and laboratory characteristics of AFM cases that occurred during peak (2016 and 2018, n = 366) and nonpeak (2015 and 2017, n = 50) years. AFM patients in peak years were younger (5.2 years) than those in nonpeak years (8.3 years). A higher percentage of patients in peak years than nonpeak years had pleocytosis (86% vs. 60%), upper extremity involvement (33% vs. 16%), and an illness preceding limb weakness (90% vs. 62%) and were positive for enterovirus or rhinovirus RNA (38% vs. 16%). Enterovirus D68 infection was associated with AFM only in peak years. Our findings suggest AFM etiology differs between peak and nonpeak years.

Acute flaccid myelitis in Canada, 2018 to 2019

Starting in 2014, biennial clusters of acute flaccid myelitis (AFM), frequently described as "polio-like" illness, have been reported across the United States and elsewhere, often linked to enteroviruses. To assess AFM trends in Canada, we reviewed the Canadian Acute Flaccid Paralysis Surveillance System (CAFPSS) for cases reported during the 2018 and 2019 calendar years that meet the Centers for Disease Control and Prevention case definitions for AFM. A total of 10 cases (8 in 2018 and 2 in 2019) met the confirmed AFM case definition and 30 (26 in 2018 and 4 in 2019) met the probable AFM case definition. Sixty percent of confirmed and probable cases were younger than five years old, and all cases had symptom onset between the months of July and October. Enteroviruses were detected in 50% of confirmed cases. At the time of writing this report, 2020 AFM data were not yet available; it is unknown if a spike in AFM cases will be seen in 2020.

Update on acute flaccid myelitis: recognition, reporting, aetiology and outcomes

Acute flaccid myelitis, defined by acute flaccid limb weakness in the setting of grey matter lesions of the spinal cord, became increasingly recognised in 2014 following outbreaks in Colorado and California, temporally associated with an outbreak of enterovirus D68 respiratory disease. Since then, there have been biennial increases in late summer/early fall. A viral infectious aetiology, most likely enteroviral, is strongly suspected, but a definitive connection has yet to be established. Patients typically present with asymmetric weakness, maximal proximally, in the setting of a febrile illness. MRI demonstrates T2/FLAIR abnormalities in the central grey matter of the spinal cord, and cerebrospinal fluid typically shows a lymphocytic pleocytosis with variable elevation in protein. The weakness may be progressive over several days and involve respiratory muscles, making early recognition and close monitoring essential. Other complications in the acute period may include autonomic instability and bowel/bladder involvement. There is no clear recommended treatment at this time, although intravenous immunoglobulin, steroids and plasma exchange have been used. Intensive therapies and rehab services have shown benefit in maximising function, and surgical interventions may be considered in cases without optimal response to therapies. Close attention should also be paid to psychosocial factors. Prognosis is generally guarded, and additional factors that predict final outcome, including host factors and treatment effects, have yet to be elucidated. Multicentre collaborative efforts will be required to provide answers about this rare but serious disorder.

Enterovirus D68-Associated Acute Flaccid Myelitis, United States, 2020

Acute flaccid myelitis (AFM) is a serious neurologic condition that causes limb weakness or paralysis in previously healthy children. Since clusters of cases were first reported in 2014, nationwide surveillance has demonstrated sharp increases in AFM cases in the United States every 2 years, most occurring during late summer and early fall. Given this current biennial pattern, another peak AFM season is expected during fall 2020 in the United States. Scientific understanding of the etiology and the factors driving the biennial increases in AFM has advanced rapidly in the past few years, although areas of uncertainty remain. The Centers for Disease Control and Prevention and AFM partners are focused on answering key questions about AFM epidemiology and mechanisms of disease. This article summarizes the current understanding of AFM etiology and outlines priorities for surveillance and research as we prepare for a likely surge in cases in 2020.

Biennial Upsurge and Molecular Epidemiology of Enterovirus D68 Infection in New York, USA, 2014 to 2018

Enterovirus D68 (EV-D68) infection has been associated with outbreaks of severe respiratory illness and increased cases of nonpolio acute flaccid myelitis. The patterns of EV-D68 circulation and molecular epidemiology are not fully understood. In this study, nasopharyngeal (NP) specimens collected from patients in the Lower Hudson Valley, New York, from 2014 to 2018 were examined for rhinovirus/enterovirus (RhV/EV) by the FilmArray respiratory panel. Selected RhV/EV-positive NP specimens were analyzed using two EV-D68-specific real-time RT-PCR assays, Sanger sequencing and metatranscriptomic next-generation sequencing. A total of 2,398 NP specimens were examined. EV-D68 was detected in 348 patients with NP specimens collected in 2014 (n = 94), 2015 (n = 0), 2016 (n = 160), 2017 (n = 5), and 2018 (n = 89), demonstrating a biennial upsurge of EV-D68 infection in the study area. Ninety-one complete or nearly complete EV-D68 genome sequences were obtained. Genomic analysis of these EV-D68 strains revealed dynamics and evolution of circulating EV-D68 strains since 2014. The dominant EV-D68 strains causing the 2014 outbreak belonged to subclade B1, with a few belonging to subclade B2. New EV-D68 subclade B3 strains emerged in 2016 and continued in circulation in 2018. Clade D strains that are rarely detected in the United States also arose and spread in 2018. The establishment of distinct viral strains and their variable circulation patterns provide essential information for future surveillance, diagnosis, vaccine development, and prediction of EV-D68-associated disease prevalence and potential outbreaks.

Vital Signs: Clinical Characteristics of Patients with Confirmed Acute Flaccid Myelitis, United States, 2018

Background

Acute flaccid myelitis (AFM) is a serious neurologic syndrome that affects mostly children and is characterized by the acute onset of limb weakness or paralysis. Since U.S. surveillance for AFM began in 2014, reported cases have peaked biennially. This report describes the clinical characteristics of AFM patients during 2018, the most recent peak year.

Methods

Medical records from persons meeting AFM clinical criterion (acute onset of flaccid limb weakness) were submitted to CDC. Patients with confirmed AFM met the clinical criterion and had magnetic resonance imaging indicating spinal cord lesions largely restricted to gray matter and spanning one or more vertebral segments. Symptoms, physical findings, test and imaging results, and hospitalization data were abstracted and described.

Results

Among 238 patients with confirmed AFM during 2018, median age was 5.3 years. Among the 238 patients, 205 (86%) had onset during August–November. Most (92%) had prodromal fever, respiratory illness, or both beginning a median of 6 days before weakness onset. In addition to weakness, common symptoms at clinical evaluation were gait difficulty (52%), neck or back pain (47%), fever (35%), and limb pain (34%). Among 211 who were outpatients when weakness began, most (76%) sought medical care within 1 day, and 64% first sought treatment at an emergency department. Overall, 98% of patients were hospitalized, 54% were admitted to an intensive care unit, and 23% required endotracheal intubation and mechanical ventilation.

Conclusion

Clinicians should suspect AFM in children with acute flaccid limb weakness, especially during August–November and when accompanied by neck or back pain and a recent history of febrile respiratory illness. Increasing awareness in frontline settings such as emergency departments should aid rapid recognition and hospitalization for AFM.

Human antibodies neutralize enterovirus D68 and protect against infection and paralytic disease

Enterovirus D68 (EV-D68) causes outbreaks of respiratory illness, and there is increasing evidence that it causes outbreaks of acute flaccid myelitis (AFM). There are no licensed therapies to prevent or treat EV-D68 infection or AFM disease. We isolated a panel of EV-D68-reactive human monoclonal antibodies that recognize diverse antigenic variants from participants with prior infection. One potently neutralizing cross-reactive antibody, EV68-228, protected mice from respiratory and neurologic disease when given either before or after infection. Cryo-electron microscopy studies revealed that EV68-228 and another potently neutralizing antibody (EV68-159) bound around the fivefold or threefold axes of symmetry on virion particles, respectively. The structures suggest diverse mechanisms of action by these antibodies. The high potency and effectiveness observed in vivo suggest that antibodies are a mechanistic correlate of protection against AFM disease and are candidates for clinical use in humans with EV-D68 infection.

Molecular Pathogenicity of Enteroviruses Causing Neurological Disease

Enteroviruses are single-stranded positive-sense RNA viruses that primarily cause self-limiting gastrointestinal or respiratory illness. In some cases, these viruses can invade the central nervous system, causing life-threatening neurological diseases including encephalitis, meningitis and acute flaccid paralysis (AFP). As we near the global eradication of poliovirus, formerly the major cause of AFP, the number of AFP cases have not diminished implying a non-poliovirus etiology. As the number of enteroviruses linked with neurological disease is expanding, of which many had previously little clinical significance, these viruses are becoming increasingly important to public health. Our current understanding of these non-polio enteroviruses is limited, especially with regards to their neurovirulence. Elucidating the molecular pathogenesis of these viruses is paramount for the development of effective therapeutic strategies. This review summarizes the clinical diseases associated with neurotropic enteroviruses and discusses recent advances in the understanding of viral invasion of the central nervous system, cell tropism and molecular pathogenesis as it correlates with host responses.

A ten-year retrospective evaluation of acute flaccid myelitis at 5 pediatric centers in the United States, 2005-2014

Background

Acute flaccid myelitis (AFM) is a severe illness similar to paralytic poliomyelitis. It is unclear how frequently AFM occurred in U.S. children after poliovirus elimination. In 2014, an AFM cluster was identified in Colorado, prompting passive US surveillance that yielded 120 AFM cases of unconfirmed etiology. Subsequently, increased reports were received in 2016 and 2018. To help inform investigations on causality of the recent AFM outbreaks, our objective was to determine how frequently AFM had occurred before 2014, and if 2014 cases had different characteristics.

Methods

We conducted a retrospective study covering 2005–2014 at 5 pediatric centers in 3 U.S. regions. Possible AFM cases aged ≤18 years were identified by searching discharge ICD-9 codes and spinal cord MRI reports (>37,000). Neuroradiologists assessed MR images, and medical charts were reviewed; possible cases were classified as AFM, not AFM, or indeterminate.

Results

At 5 sites combined, 26 AFM cases were identified from 2005–2013 (average annual number, 3 [2.4 cases/100,000 pediatric hospitalizations]) and 18 from 2014 (12.6 cases/100,000 hospitalizations; Poisson exact p<0.0001). A cluster of 13 cases was identified in September–October 2014 (temporal scan p = 0.0001). No other temporal or seasonal trend was observed. Compared with cases from January 2005–July 2014 (n = 29), cases from August–December 2014 (n = 15) were younger (p = 0.002), more frequently had a preceding respiratory/febrile illness (p = 0.03), had only upper extremities involved (p = 0.008), and had upper extremity monoplegia (p = 0.03). The cases had higher WBC counts in cerebrospinal fluid (p = 0.013).

Conclusion

Our data support emergence of AFM in 2014 in the United States, and those cases demonstrated distinctive features compared with preceding sporadic cases.

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.

A survey of known immune epitopes in the enteroviruses strains associated with acute flaccid myelitis

Enteroviruses are potentially linked to the emergence of Acute Flaccid Myelitis (AFM), a rare but very serious condition that affects the nervous system. AFM has been associated with coxsackievirus A16, enterovirus A71 (EVA71) and enterovirus D68 (EVD68). Little is known about host-pathogen interactions for these viruses, and whether immune responses may have a protective or immunopathological role in disease presentations. Towards addressing this issue, we used the Immune Epitope Database to assess the known inventory of B and T cell epitopes from enteroviruses, focusing on data related to human hosts. The extent of conservation in areas that are targets of B and T cell immune responses were examined. This analysis sheds light on regions of the enterovirus polypeptide that can be probed to induce a specific or cross-reactive B or T cell the immune response to enteroviruses, with a particular focus on coxsackievirus A16, EVA71 and EVD68. In addition, these analyses reveal the current gap-of-knowledge in the T and B cell immune responses that future studies should aim to address.