Polio-Like Illness Associated With Outbreak of Upper Respiratory Tract Infection in Children

Acute Flaccid Myelitis: Review of Clinical Features, Diagnosis, and Management with Nerve Transfers

BACKGROUND

Acute flaccid myelitis (AFM) is a devastating neurologic condition in children, manifesting as acute limb weakness and/or paralysis. Despite increased awareness of AFM following initiation of U.S. surveillance in 2014, no treatment consensus exists. The purpose of this systematic review was to summarize the most current knowledge regarding AFM epidemiology, cause, clinical features, diagnosis, and supportive and operative management, including nerve transfer.

METHODS

The authors systematically reviewed the literature based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using multiple databases to search the keywords ("acute flaccid myelitis"), ('acute flaccid myelitis'/exp OR 'acute flaccid myelitis'), and (Acute AND flaccid AND myelitis). Included articles reported on (1) AFM diagnosis and (2) patient-specific data regarding epidemiology, cause, clinical features, diagnostic features, or management of AFM.

RESULTS

Ninety-nine articles were included in this review. The precise cause and pathophysiologic mechanism of AFM remain undetermined, but AFM is strongly associated with nonpolio enterovirus infections. Clinical presentation typically comprises preceding viral prodrome, pleocytosis, spinal cord lesions on T2-weighted magnetic resonance imaging, and acute onset of flaccid weakness/paralysis with hyporeflexia in at least one extremity. Supportive care includes medical therapy and rehabilitation. Early studies of nerve transfer for AFM have shown favorable outcomes for patients with persistent weakness.

CONCLUSIONS

Supportive care and physical therapy are the foundation of a multidisciplinary approach to managing AFM. For patients with persistent limb weakness, nerve transfer has shown promise for improving function in distal muscle groups. Surgeons must consider potential spontaneous recovery, patient selection, donor nerve availability, recipient nerve appropriateness, and procedure timing.

Acute flaccid myelitis: cause, diagnosis, and management

Acute flaccid myelitis (AFM) is a disabling, polio-like illness mainly affecting children. Outbreaks of AFM have occurred across multiple global regions since 2012, and the disease appears to be caused by non-polio enterovirus infection, posing a major public health challenge. The clinical presentation of flaccid and often profound muscle weakness (which can invoke respiratory failure and other critical complications) can mimic several other acute neurological illnesses. There is no single sensitive and specific test for AFM, and the diagnosis relies on identification of several important clinical, neuroimaging, and cerebrospinal fluid characteristics. Following the acute phase of AFM, patients typically have substantial residual disability and unique long-term rehabilitation needs. In this Review we describe the epidemiology, clinical features, course, and outcomes of AFM to help to guide diagnosis, management, and rehabilitation. Future research directions include further studies evaluating host and pathogen factors, including investigations into genetic, viral, and immunological features of affected patients, host-virus interactions, and investigations of targeted therapeutic approaches to improve the long-term outcomes in this population.

Neurotropism of Enterovirus D68 Isolates Is Independent of Sialic Acid and Is Not a Recently Acquired Phenotype

Since 2014, numerous outbreaks of childhood infections with enterovirus D68 (EV-D68) have occurred worldwide. Most infections are associated with flu-like symptoms, but paralysis may develop in young children. It has been suggested that infection only with recent viral isolates can cause paralysis. To address the hypothesis that EV-D68 has recently acquired neurotropism, murine organotypic brain slice cultures, induced human motor neurons and astrocytes, and mice lacking the alpha/beta interferon receptor were infected with multiple virus isolates. All EV-D68 isolates, from 1962 to the present, can infect neural cells, astrocytes, and neurons. Furthermore, our results show that sialic acid binding does not play a role in EV-D68 neuropathogenesis. The study of EV-D68 infection in organotypic brain slice cultures, induced motor neurons, and astrocytes will allow for the elucidation of the mechanism by which the virus infection causes disease.

Acute flaccid myelitis (AFM) is a rare but serious illness of the nervous system, specifically affecting the gray matter of the spinal cord, motor-controlling regions of the brain, and cranial nerves. Most cases of AFM are pathogen associated, typically with poliovirus and enterovirus infections, and occur in children under the age of 6 years. Enterovirus D68 (EV-D68) was first isolated from children with pneumonia in 1962, but an association with AFM was not observed until the 2014 outbreak. Organotypic mouse brain slice cultures generated from postnatal day 1 to 10 mice and adult ifnar knockout mice were used to determine if neurotropism of EV-D68 is shared among virus isolates. All isolates replicated in organotypic mouse brain slice cultures, and three isolates replicated in primary murine astrocyte cultures. All four EV-D68 isolates examined caused paralysis and death in adult ifnar knockout mice. In contrast, no viral disease was observed after intracranial inoculation of wild-type mice. Six of the seven EV-D68 isolates, including two from 1962 and four from the 2014 outbreak, replicated in induced human neurons, and all of the isolates replicated in induced human astrocytes. Furthermore, a putative viral receptor, sialic acid, is not required for neurotropism of EV-D68, as viruses replicated within neurons and astrocytes independent of binding to sialic acid. These observations demonstrate that EV-D68 is neurotropic independent of its genetic lineage and can infect both neurons and astrocytes and that neurotropism is not a recently acquired characteristic as has been suggested. Furthermore, the results show that in mice the innate immune response is critical for restricting EV-D68 disease.

Acute Flaccid Myelitis: A Clinical Overview for 2019

Acute flaccid myelitis (AFM) is characterized by flaccid paralysis of one or more limbs, often following a viral illness, with magnetic resonance imaging findings consistent with inflammation of the spinal cord gray matter. It is unclear whether all patients with AFM will have full recovery of neurologic function. Since 2014, there have been several clusters of AFM in the United States, with a 3-fold increase in reported AFM cases recorded in 2018 compared with the previous year. Epidemiological evidence supports a temporal association between respiratory enteroviral illness, particularly with enteroviruses D68 and A71, and clustering of AFM cases. However, causality has yet to be established. Treatment of AFM is primarily supportive. Adjunctive therapies such as intravenous immunoglobulin, corticosteroids, plasmapheresis, and fluoxetine have not been found to improve long-term outcomes. Further research is urgently needed to characterize and optimize management of this emerging, yet poorly understood, condition.

Acute flaccid myelitis caused by enterovirus D68: Case definitions for use in clinical practice

Acute flaccid myelitis (AFM) was increasingly detected in recent years, coinciding with upsurges of enterovirus D68 (EV-D68) infections. We reviewed the evidence for a causal relationship between both. Based on reported cases, we provide case definitions for AFM caused by EV-D68 infections to enable a standard procedure for affected patients. Current case definitions are focussing on epidemiological aspects but clinical case definitions are still missing. We propose the following case definitions to be used in clinical practice in order to mirror clinical realities and facilitate a common systematic approach in case management: A possible case is defined as a person presenting with either acute myelitis/paralysis or Guillain-Barré Syndrome (GBS), particularly during periods of EV-D68 circulation. A probable case is defined as a person presenting with symptoms of either acute myelitis/paralysis or GBS and at least one of the following criteria: i) MRI abnormality representing with T2 hyperintensity in spinal cord grey matter with or without hyperintensity at dorsal brain stem, ii) investigations showing an axonal neuropathy including reduced compound motor action potentials with normal conduction velocities and absence of conduction blocks compatible with anterior horn cell disease or iii) detection of enteroviruses in a respiratory specimen obtained from the lower respiratory tract during periods of EV-D68 circulation. A confirmed case is defined as a person presenting with acute flaccid myelitis/paralysis, MRI abnormality and detection of enterovirus-D68-specific nucleic acids in a respiratory specimen using a validated PCR assay targeting the VP1 gene with subsequent sequencing and typing.

Evaluation of antiviral therapies in respiratory and neurological disease models of Enterovirus D68 infection in mice

Enterovirus D68 (EV-D68) is unique among enteroviruses because of the ability to cause severe respiratory disease as well as neurological disease. We developed separate models of respiratory and neurological disease following EV-D68 infection in AG129 mice that respond to antiviral treatment with guanidine. In four-week-old mice infected intranasally, EV-D68 replicates to high titers in lung tissue increasing the proinflammatory cytokines MCP-1 and IL-6. The respiratory infection also produces an acute viremia. In 10-day-old mice infected intraperitoneally, EV-D68 causes a neurological disease with weight-loss, paralysis, and mortality. In our respiratory model, treatment with guanidine provides a two-log reduction in lung virus titers, reduces MCP-1 and IL-6, and prevents histological lesions in the lungs. Importantly, viremia is prevented by early treatment with guanidine. In our neurological model, guanidine treatment protects mice from weight-loss, paralysis, and mortality. These results demonstrate the utility of these models for evaluation of antiviral therapies for EV-D68 infection.

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.

Acute Flaccid Myelitis in German Children in 2016-the Return of Polio?

BACKGROUND

Although poliomyelitis has almost been eradicated worldwide, cases of a polio-like disease with asymmetrical flaccid paralysis of variable severity have been seen repeatedly in recent years.

METHODS

Data were collected on children treated in hospitals in the German federal states of Bavaria and Lower Saxony in 2016. The frequency of disease across Germany was estimated on the basis of voluntary reporting to the Robert Koch Institute. 16 cases were registered there for the entire year 2016.

RESULTS

7 children with flaccid paralysis of acute onset were treated in the participating hospitals in the summer and fall of 2016. We describe two illustrative cases, one with a mild course and one with a severe course. Rapid diagnosis requires not only clinical neurological assessment but also neurophysiological studies, magnetic resonance imaging (MRI), and targeted microbiological testing. The characteristic features include damage to the anterior horn of the spinal cord that can be seen on MRI and/or electrophysiologically demonstrable abnormalities indicating motor neuron damage. A pathogen can hardly ever be identified in the cerebrospinal fluid, but the epidemiological context and the detection of viruses in the stool or respiratory secretions indicate that entero - viruses may be responsible.

CONCLUSION

The prognosis of this disease cannot be reliably assessed at first, and no specific treatment is currently available.

Enterovirus D68 and acute flaccid myelitis-evaluating the evidence for causality

Increased circulation of enterovirus D68 in 2014 and 2016 temporally and geographically coincided with increases in cases of acute flaccid myelitis, an uncommon condition of paralysis due to lesions in the anterior horn of the spinal cord. The identification of enterovirus D68 in respiratory specimens from cases of acute flaccid myelitis worldwide further supports an association, yet the absence of direct virus isolation from affected tissues, infrequent detection in cerebrospinal fluid, and the absence, until recently, of an animal model has left the causal nature of the relationship unproven. In this Personal View we evaluate epidemiological and biological evidence linking enterovirus D68 and acute flaccid myelitis. We applied the Bradford Hill criteria to investigate the evidence for a causal relationship and highlight the importance of comprehensive surveillance and research to further characterise the role of enterovirus D68 in acute flaccid myelitis and pursue effective therapies and prevention strategies.

The association between acute flaccid myelitis (AFM) and Enterovirus D68 (EV-D68) - what is the evidence for causation?

BackgroundEnterovirus D68 (EV-D68) has historically been a sporadic disease, causing occasional small outbreaks of generally mild infection. In recent years, there has been evidence of an increase in EV-D68 infections globally. Large outbreaks of EV-D68, with thousands of cases, occurred in the United States, Canada and Europe in 2014. The outbreaks were associated temporally and geographically with an increase in clusters of acute flaccid myelitis (AFM).
Aims: We aimed to evaluate a causal association between EV-D68 and AFM. 
Methods: Using data from the published and grey literature, we applied the Bradford Hill criteria, a set of nine principles applied to examine causality, to evaluate the relationship between EV-D68 and AFM. Based on available evidence, we defined the Bradford Hill Criteria as being not met, or met minimally, partially or fully. 
Results: Available evidence applied to EV-D68 and AFM showed that six of the Bradford Hill criteria were fully met and two were partially met. The criterion of biological gradient was minimally met. The incidence of EV-D68 infections is increasing world-wide. Phylogenetic epidemiology showed diversification from the original Fermon and Rhyne strains since the year 2000, with evolution of a genetically distinct outbreak strain, clade B1. Clade B1, but not older strains, is associated with AFM and is neuropathic in animal models. 
Conclusion: While more research is needed on dose-response relationship, application of the Bradford Hill criteria supported a causal relationship between EV-D68 and AFM.

Evaluating Treatment Efficacy in a Mouse Model of Enterovirus D68-Associated Paralytic Myelitis

Background

Enterovirus D68 (EV-D68)-associated acute flaccid myelitis (AFM) is a devastating neurological disease for which there are no treatments of proven efficacy. The unpredictable temporal and geographic distribution of cases and the rarity of the disease make it unlikely that data from randomized controlled trials will be available to guide therapeutic decisions. We evaluated the following 3 widely used empirical therapies for the ability to reduce the severity of paralysis in a mouse model of EV-D68 infection: (1) human intravenous immunoglobulin (hIVIG), (2) fluoxetine, and (3) dexamethasone.

Methods

Neonatal mice were injected intramuscularly with a human 2014 EV-D68 isolate that reliably induces paralysis in mice due to infection and loss of spinal cord motor neurons. Mice receiving treatments were evaluated for motor impairment, mortality, and spinal cord viral load.

Results

hIVIG, which contained neutralizing antibodies to EV-D68, reduced paralysis in infected mice and decreased spinal cord viral loads. Fluoxetine had no effect on motor impairment or viral loads. Dexamethasone treatment worsened motor impairment, increased mortality, and increased viral loads.

Conclusion

Results in this model of EV-D68-associated AFM provide a rational basis for selecting empirical therapy in humans and establish this model as a useful system for evaluating other potential therapies.

Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016

OBJECTIVE

To report a outbreak of 11 cases of acute asymmetric flaccid myelopathy due to spinal motor neuron injury.

MATERIAL AND METHODS

Eleven children, six male, with a mean age of 3 years presented with acute flaccid myelitis. We analyzed clinical features, etiology, neuroradiological images, treatment, and outcome.

RESULTS

Nine children had bilateral and asymmetric flaccid myelitis of the upper limbs, 1 had upper limb monoplegia, and 1 presented with hemiparesis. The cranial nerves were involved in 6 patients and 4 required mechanical ventilation. In all cases acute flaccid myelitis co-occurred with upper airway infection and/or fever. Spinal cord magnetic resonance imaging was abnormal in all, showing 2 different patterns: A linear pattern involving the anterior horns and another that was more heterogeneous showing spinal cord expansion. The lesions were non-enhancing in all. In 5/11 patients involvement of the medulla oblongata and pons was also observed. None of the patients presented with supratentorial lesions. In 4/11 children, the human enterovirus subtype D68 (HEV-D68) was identified in the airway and in 1/11 in the cerebrospinal fluid as well. In the remaining patients different enterovirus species A, B, and C variants were detected, as well as rhinovirus in 1 and influenza in another. Ten children received treatment with intravenous immunoglobulin and steroids and 4 of these children also underwent plasma exchange. Treatment did not lead to clinical improvement.

CONCLUSIONS

In a patient with acute flaccid myelitis, HEV-D68 infection should be ruled out. Cases in which the virus was not detected were considered as "false negatives" as samples were collected late in course of the disease. The lack of response to anti-inflammatory and immunomodulatory treatment suggests a direct viral mechanism. This study is to our knowledge the first on an HEV-D68-infection-related cluster in Latin America.

Isolation of an Enterovirus D68 from Blood from a Child with Pneumonia in Rural Haiti: Close Phylogenetic Linkage with New York Strain

We report the detection and isolation of enterovirus D68 from the blood of a 6-year-old child in rural Haiti, who presented with high fever and clinical signs suggestive of pneumonia. On phylogenetic analysis, this Haitian isolate was virtually identical to an enterovirus D68 strain circulating in New York during the same time period.

Acute flaccid myelitis: A clinical review of US cases 2012-2015

This review highlights clinical features of the increasing cases of acute flaccid paralysis associated with anterior myelitis noted in the United States from 2012 to 2015. Acute flaccid myelitis refers to acute flaccid limb weakness with spinal cord gray matter lesions on imaging or evidence of spinal cord motor neuron injury on electrodiagnostic testing. Although some individuals demonstrated improvement in motor weakness and functional deficits, most have residual weakness a year or more after onset. Epidemiological evidence and biological plausibility support an association between enterovirus D68 and the recent increase in acute flaccid myelitis cases in the United States. Ann Neurol 2016;80:326-338.

Complete Genome Sequence of Enterovirus D68 Detected in Classroom Air and on Environmental Surfaces

We amplified and sequenced the complete genome of enterovirus D68 (EV-D68) that had been collected from classroom air using a filter-based air sampling method and by swab sampling of environmental surfaces. Relatively high levels of EV-D68 genome equivalents were found per cubic meter of air by quantitative real-time reverse transcription-PCR (RT-PCR).

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.

Neurotropic Enterovirus Infections in the Central Nervous System

Enteroviruses are a group of positive-sense single stranded viruses that belong to the Picornaviridae family. Most enteroviruses infect humans from the gastrointestinal tract and cause mild symptoms. However, several enteroviruses can invade the central nervous system (CNS) and result in various neurological symptoms that are correlated to mortality associated with enteroviral infections. In recent years, large outbreaks of enteroviruses occurred worldwide. Therefore, these neurotropic enteroviruses have been deemed as re-emerging pathogens. Although these viruses are becoming large threats to public health, our understanding of these viruses, especially for non-polio enteroviruses, is limited. In this article, we review recent advances in the trafficking of these pathogens from the peripheral to the central nervous system, compare their cell tropism, and discuss the effects of viral infections in their host neuronal cells.