The arrowheads point to the findings in A through F. A, T2-weighted signal hyperintensity and expansion. B, Gadolinium enhancement. C, Gadolinium enhancement. The arrowhead is sitting over the L2/L3 intervertebral space. D, Restricted diffusion. E, Apparent diffusion coefficient map. F, T2-weighted signal hyperintensity.
An 18-month-old patient was seen at the hospital with a 2-day history of fever, anorexia, and vomiting. On examination, she was in shock, with supraventricular tachycardia (225 beats/min). There was ptosis and rightward deviation of the left eye, as well as right eye nystagmus. She had cardiac arrest in the emergency department and was unable to be resuscitated. A, Shown are marked and widespread microglial activation and microglial nodules (immunostained for major histocompatibility complex class II antigens [CR3/43]). B, Foci of necrosis (asterisk) with perivascular lymphocytes (hematoxylin-eosin) are shown. C, Shown are microglial nodules (arrowheads) (hematoxylin-eosin).
DWI indicates diffusion-weighted imaging; IVIG, intravenous immunoglobulin; MRS, modified Rankin Scale score; WHO, World Health Organization.
eTable. Clinical Classification of Patients With EV71 Neurological Disease
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Teoh H, Mohammad SS, Britton PN, et al. Clinical Characteristics and Functional Motor Outcomes of Enterovirus 71 Neurological Disease in Children. JAMA Neurol. 2016;73(3):300–307. doi:10.1001/jamaneurol.2015.4388
Enterovirus 71 (EV71) causes a spectrum of neurological complications with significant morbidity and mortality. Further understanding of the characteristics of EV71-related neurological disease, factors related to outcome, and potential responsiveness to treatments is important in developing therapeutic guidelines.
To further characterize EV71-related neurological disease and neurological outcome in children.
Design, Setting, and Participants
Prospective 2-hospital (The Sydney Children’s Hospitals Network) inpatient study of 61 children with enterovirus-related neurological disease during a 2013 outbreak of EV71 in Sydney, Australia. The dates of our analysis were January 1, to June 30, 2013.
Main Outcomes and Measures
Clinical, neuroimaging, laboratory, and pathological characteristics, together with treatment administered and functional motor outcomes, were assessed.
Among 61 patients, there were 4 precipitous deaths (7%), despite resuscitation at presentation. Among 57 surviving patients, the age range was 0.3 to 5.2 years (median age, 1.5 years), and 36 (63%) were male. Fever (100% [57 of 57]), myoclonic jerks (86% [49 of 57]), ataxia (54% [29 of 54]), and vomiting (54% [29 of 54]) were common initial clinical manifestations. In 57 surviving patients, EV71 neurological disease included encephalomyelitis in 23 (40%), brainstem encephalitis in 20 (35%), encephalitis in 6 (11%), acute flaccid paralysis in 4 (7%), and autonomic dysregulation with pulmonary edema in 4 (7%). Enterovirus RNA was more commonly identified in feces (42 of 44 [95%]), rectal swabs (35 of 37 [95%]), and throat swabs (33 of 39 [85%]) rather than in cerebrospinal fluid (10 of 41 [24%]). Magnetic resonance imaging revealed characteristic increased T2-weighted signal in the dorsal pons and spinal cord. All 4 patients with pulmonary edema (severe disease) demonstrated dorsal brainstem restricted diffusion (odds ratio, 2; 95% CI, 1-4; P = .001). Brainstem or motor dysfunction had resolved in 44 of 57 (77%) at 2 months and in 51 of 57 (90%) at 12 months. Focal paresis was evident in 23 of 57 (40%) at presentation and was the most common persisting clinical and functional problem at 12 months (observed in 5 of 6 patients), with 1 patient also requiring invasive ventilation. Patients initially seen with acute flaccid paralysis or pulmonary edema had significantly greater frequencies of motor dysfunction at follow-up compared with patients initially seen with other syndromes (odds ratio, 15; 95% CI, 3-79; P < .001).
Conclusions and Relevance
Enterovirus 71 may cause serious neurological disease in young patients. The distinct clinicoradiological syndromes, predominantly within the spinal cord and brainstem, enable rapid recognition within evolving outbreaks. Long-term functional neurological morbidity is associated with paresis linked to involvement of gray matter in the brainstem or spinal cord.
Enterovirus 71 (EV71) has emerged as a significant infectious cause of severe neurological disease, with a potentially profound effect on infected patients. Large outbreaks continue to be a significant public health concern.1 Enterovirus 71 typically causes uncomplicated hand-foot-and-mouth disease. However, a few patients will develop neurological complications, including aseptic meningitis, acute flaccid paralysis, and fatal brainstem encephalitis.1-4 The World Health Organization (WHO) published comprehensive guidelines5 detailing a clinical classification system of EV71-related neurological disease and suggested treatment strategies. Evidence-based therapeutic guidelines have yet to be developed, to our knowledge. Most important, the results of several retrospective observational studies1,4,6 suggest that intravenous immunoglobulin (IVIG) may improve outcome and reduce mortality in EV71 neurological disease. Consequently, a recommendation to consider immunotherapies in severe EV71 infection has evolved, and IVIG is frequently used to treat patients with severe cases.5,6 Early clinical and laboratory identification of patients with potentially severe EV71 neurological disease is a high priority. Several clinical variables at presentation have been suggested to predict progressive and severe disease,1,4,7-9 but these factors need to be prospectively validated.
Human and primate pathological specimens demonstrate that EV71 is neurotropic,10-13 and the viral distribution is distinct and stereotyped. Direct viral infection and inflammation are largely restricted to neurons in the spinal gray matter, dorsal brainstem, dentate nucleus of the cerebellum, hypothalamus, and subthalamic nucleus.12,14,15 At the most severe end of the spectrum, extensive involvement of the medulla, including the tractus solitarius and nucleus ambiguous, with inflammation, edema, and neuronal loss results in neurogenic pulmonary edema and cardiopulmonary failure, with collapse that is often fatal.12,16
In 2013, an outbreak of EV71 occurred in Sydney, Australia. Patients’ debilitating morbidity and physicians’ clinical experience after the 2001 local EV71 outbreak17 prompted the present study. The objective was to further characterize EV71-related neurological disease, factors related to outcome, and potential responsiveness to disease-modifying immunotherapy.
Questions: Can we characterize enterovirus 71 neurological disease using the WHO guideline in an outbreak and describe its long term neurological outcome?
Findings: This prospective observational study included 61 children with enterovirus 71 neurological disease. The neurological syndromes included 40% encephalomyelitis, 35% brainstem encephalitis, 11% encephalitis, 7% acute flaccid paralysis and 7% autonomic dysregulation with pulmonary edema. Focal paresis was evident in 40% at presentation and was observed to be the most common persisting functional problem at 12 months.
Meaning: Rapid recognition of enterovirus 71 neurological disease within an evolving outbreak is recognizable using distinct clinicoradiological syndromes.
The present study included 61 children with EV71 neurological disease (age range, 0-16 years) managed through The Sydney Children’s Hospitals Network during an outbreak between January 1, and June 30, 2013. The Sydney Children’s Hospitals Network Human Research Ethics Committee approved the study. Verbal informed consent was obtained from parents or carers. Inclusion criteria were clinical diagnosis of encephalitis, encephalomyelitis, acute flaccid paralysis, or brainstem encephalitis, with confirmed enterovirus infection. The latter required isolation of enterovirus with standard nucleic acid amplification from multiple sites during acute presentation. Enterovirus 71 typing was undertaken in a subset of cases.
After early recognition of the outbreak, detailed clinical and demographic data were prospectively collected on all patients with suspected EV71 neurological disease. Clinical classification of EV71 neurological disease was based on WHO guidelines5 and comprised involvement of the central nervous system (CNS) with or without the autonomic nervous system and with or without pulmonary edema. Subgroups of CNS involvement included brainstem encephalitis, acute flaccid paralysis, encephalitis, and encephalomyelitis (eTable in the Supplement).
Laboratory tests at presentation included hematology, biochemistry and cerebrospinal fluid (CSF) microscopy, and bacterial culture. The result of enterovirus nucleic acid testing of each sample collected (feces, CSF, serum, nasopharyngeal aspirate, throat swab, and rectal swab) was documented for all patients to maximize diagnosis and determine the diagnostic yield for different specimen sites. Molecular testing of virological specimens was performed for common causes of pediatric encephalitis, including human herpesvirus 1 and 2, Epstein-Barr virus, cytomegalovirus, and varicella-zoster virus. Autopsy was performed on 2 deceased patients.
Viral RNA was extracted from 200 μL of clinical specimen using a kit (MagNA Pure LC Total Nucleic Acid Isolation; Roche) on a specialized instrument (MagNA Pure LC; Roche). The enterovirus subtype was determined using polymerase chain reaction sequencing of the VP 1 region and 5′ untranslated region as performed previously,17,18 which accurately identifies genotype. The amplicons were detected by agarose gel electrophoresis. DNA templates were sequenced with a cycle sequencing kit (BigDye Terminator, version 3.1; Applied Biosystems) on a DNA analyzer (AB3730 DNA; Applied Biosystems) using primers EV2 and EV3. Human EV71 identification was achieved by submitting the sequences to a Basic Local Alignment Search Tool (BLAST) search of sequences (GenBank; National Center for Biotechnology Information) and determining maximal homology.
Magnetic resonance imaging (MRI) sequences included axial and sagittal T1-weighted and T2-weighted, fluid-attenuated inversion recovery, diffusion-weighted imaging, and postgadolinium images. When available, brain and spine MRIs were independently reviewed by 2 neurologists who were masked to the radiological report and clinical syndrome. If consensus was not reached, the opinion of a third neurologist was obtained.
Medical therapy conformed to the 2011 WHO management guidelines5 recommending supportive care and consideration of IVIG therapy in severe cases. Administration of IVIG (1 g/kg/d for 2 days) was at the discretion of the treating neurologist. High-dose corticosteroids in the form of methylprednisolone (20-30 mg/kg/d for 3-5 days) or dexamethasone (0.4 mg/kg/d for 2 days) were prescribed alone in some cases or together with IVIG.
Presentations were characterized according to WHO classification5 at baseline. The presence or absence of ongoing brainstem or motor dysfunction at 2 months was recorded. Those with neurological dysfunction were followed up again at 12 months, and a modified Rankin Scale score19 was obtained to quantify disability (0 is normal, 1 is mild symptoms and no disability, 2 is slight disability, 3 is moderate disability and ability to walk independently, 4 is moderate severe disability and ability to walk with assistance, 5 is severe disability and inability to walk, and 6 is death).
Descriptive statistics were used for clinical features, WHO classification5 of neurological disease, and investigation results. To determine predictors of morbidity, associations between clinical presentations were stratified to the presence or absence of any neurological morbidity at 2 months and 12 months. Ten different variables were compared using Fisher exact test or χ2 test. Fisher exact test and odds ratios (ORs) were calculated to compare outcomes between clinical syndromes. P < .05 was considered statistically significant for all analyses.
In total, 61 patients were seen with enterovirus neurological morbidity. Four patients had cardiopulmonary collapse at initial presentation and died within several hours, despite attempted resuscitation. Enterovirus RNA was isolated from at least 1 site in all patients. The diagnostic yields for enterovirus nucleic acid test analysis were 42 of 44 (95%) in feces, 35 of 37 (95%) in rectal swabs, and 33 of 39 (85%) in throat swabs. The diagnostic yields were lower in serum (5 of 21 [24%]) and CSF (10 of 41 [24%]). The diagnostic yield of CSF was much higher in the encephalitis group (5 of 5 [100%]) compared with the rest of the cohort (5 of 37 [14%]). Enterovirus 71 typing was performed in 32 of 57 cases (56%), and all were confirmed as EV71. All 183 virological specimens were negative for the common viruses tested.
Of the 57 surviving patients, 36 were male, and the age range was 0.3 to 5.2 years old (median age, 1.5 years). The median duration of hospitalization was 6 days (range, 1-365 days). In total, 18 of 57 patients (32%) were admitted to the intensive care unit. The most common initial clinical manifestations were fever in 57 of 57 (100%), myoclonic jerks in 49 of 57 (86%), ataxia in 29 of 54 (54%), and vomiting in 29 of 54 (54%). Other symptoms and signs included limb weakness in 23 of 57 (40%), truncal weakness in 22 of 57 (39%), urinary retention in 16 of 56 (29%), seizures in 12 of 55 (22%), and cranial nerve dysfunction in 4 of 57 (7%). Autonomic dysregulation was noted in 9 of 57 (16%), including tachycardia or bradycardia, hypertension or hypotension, respiratory distress, and shock.
Using the WHO classification5 at the nadir of clinical status among the 57 survivors, encephalomyelitis was found in 23 (40%), brainstem encephalitis in 20 (35%), encephalitis in 6 (11%), acute flaccid paralysis in 4 (7%), and autonomic dysregulation with pulmonary edema in 4 (7%). In total, 8 of 23 patients (35%) with symptoms consistent with encephalomyelitis developed urinary retention. In some patients, progression of the clinical findings suggested involvement of more than 1 site, with 2 patients initially seen with acute flaccid paralysis and 2 patients initially seen with encephalomyelitis subsequently developing autonomic dysregulation and pulmonary edema.
The findings of brain and spine MRI are summarized in the Table. Neuroimaging was performed in 38 of 57 (68%), at the discretion of the treating neurologist. Brain MRI was abnormal in 24 of 38 patients (63%), with abnormalities consistently demonstrated in the dorsal brainstem (central midbrain, posterior portion of the medulla oblongata, and pons) and the dentate nuclei in the cerebellum (Figure 1) on fluid-attenuated inversion recovery and T2-weighted imaging with or without diffusion restriction (Table). These changes were not limited to patients with clinical brainstem encephalitis. All patients with pulmonary edema demonstrated restricted diffusion within the dorsal brainstem (P = .001), suggesting cytotoxic injury (Figure 1D). In contrast, supratentorial structures were abnormal in only 1 of 38 patients (3%) and were not associated with clinical encephalitis. Spine MRI was abnormal in 27 of 34 (79%), with cord or nerve root abnormalities. This abnormality was seen mainly in the encephalomyelitis group, with 19 of 21 (91%) showing spinal cord abnormalities.
The pathological findings in the brain and brainstem in 2 of the deceased patients demonstrated severe inflammation predominantly involving the medulla (Figure 2A), concordant with areas of signal abnormality in the neuroimaging of patients with pulmonary edema. Numerous perivascular and interstitial activated microglia or macrophages and lymphocytes (predominantly CD3+ T cells), scattered microglial nodules (Figure 2C), and microscopic areas of necrosis (Figure 2B) were seen. Rare foci of neuronophagia were noted although no viral inclusions or cytopathic effects were identified.
In total, 29 of 57 patients (51%) received immunomodulatory treatment, with 10 (18%) receiving IVIG in accord with WHO guidelines,5 7 (12%) receiving high-dose corticosteroids, and 12 (21%) receiving both. Patients with pulmonary edema (4 of 4 [100%]), encephalomyelitis (19 of 23 [83%]), or acute flaccid paralysis (3 of 4 [75%]) were more likely to receive immunomodulatory treatment compared with patients with brainstem encephalitis (3 of 20 [15%]) or encephalitis (0 of 6 [0%]) (Figure 3). We observed no adverse effects of immunomodulatory treatment.
Ten clinical variables were analyzed. Among them, limb weakness (OR, 9; 95% CI, 1-84; P < .05), cranial nerve dysfunction (OR, 50; 95% CI, 4-637; P < .05), and pulmonary edema (OR, 50; 95% CI, 4-637; P < .05) at presentation were predictive of morbidity at 12 months.
At 2 months’ follow-up, 13 of 57 patients (23%) had ongoing brainstem or motor dysfunction (Figure 3). Symptoms were related to the original presentation and the region of initial CNS involvement. All 4 patients with cranial nerve dysfunction demonstrated residual symptoms, consisting of ophthalmoparesis in 2 patients and bulbar palsy with respiratory insufficiency requiring invasive ventilation in 2 patients. Overall, 10 of 23 patients (44%) with limb weakness (acute flaccid paralysis or encephalomyelitis) and 2 of 29 patients (7%) with ataxia (brainstem encephalitis) had ongoing motor dysfunction. Motor dysfunction at 2 months was more common in patients initially seen with acute flaccid paralysis or pulmonary edema syndromes (OR, 15; 95% CI, 3-79; P < .001).
At a minimum of 12 months’ follow-up, 51 of 57 surviving patients (90%) had no clinical motor or brainstem neurological dysfunction. In the 6 patients with residual abnormalities at 12 months, the modified Rankin Scale score ranged from 1 to 5 (Figure 3). Most important, an additional 4 patients died within several hours of presentation, resulting in an overall survival of 93% (57 of 61). Paresis (observed in 5 patients) was the most common persisting clinical and functional problem, with 1 patient still requiring invasive ventilation and another patient having isolated sixth nerve palsy. Patients with residual limb weakness initially were seen with acute flaccid paralysis (n = 2) or pulmonary edema (n = 3). Overall, patients initially seen with acute flaccid paralysis or pulmonary edema had significantly greater odds of motor dysfunction compared with patients initially seen with the other syndromes (OR, 46; 95% CI, 4-476; P < .001). For those with limb weakness, motor function ranged from a lack of independent ambulation in 2 patients at age 24 months and 37 months, walking with orthotics support at 33 months, and walking independently with an abnormal gait and reduced endurance in 2 patients at 34 months and 52 months.
Using clinical, radiological, and pathological assessments, we have described the characteristics of EV71 neurological disease in a large cohort of pediatric patients in the context of their clinical care and documented their motor and brainstem morbidity at 2 and 12 months. Identification of distinct clinicoradiological syndromes allows rapid recognition of EV71 cases within developing outbreaks. In addition, this study demonstrates the usefulness of the 2011 WHO guidelines5 for classification and management of the disease. Overall, 89% (51 of 57) of survivors had no motor or functional impairment at 12 months. Long-term functional neurological morbidity was associated with involvement of ventral spinal gray matter or bulbar or motor cranial nerves that led to paresis. Many patients who were initially seen with limb weakness had ongoing neurological dysfunction regardless of treatment, which was also predictive of morbidity, suggesting that the nature and localization of the underlying disease process represent important contributors to medium-term and long-term outcomes, which may or may not be modulated by immunotherapy.
While clinically comparable to poliomyelitis,1 the clinicoradiological characteristics of EV71 infection reveal more widespread CNS abnormalities and suggest a selective vulnerability of ventral spinal gray matter and bulbar or motor cranial nerves. Human and animal studies14,20 have demonstrated retrograde transport of EV71 into the CNS via peripheral motor nerves and direct EV71 invasion, resulting in neuronal injury. The distinctive cellular tropism may be mediated by expression of receptors for EV71, specifically scavenger receptor class B member 2 (SCARB2) and P-selectin glycoprotein ligand, with SCARB2 expressed in neurons in the brain and spinal cord.21,22 In support of this theory, SCARB2 transgenic mice demonstrate greater susceptibility to EV71 with a resultant neurological phenotype compared with natural strains.23 Furthermore, in vivo investigations have shown that monoclonal antibodies can inhibit EV71 cellular attachment to SCARB2 and subsequent virus internalization.24 Although untested to date, it is possible that EV71 induces a secondary autoimmune response of cell surface autoantibody or other autoreactive response, as has been described in human herpesvirus encephalitis relapse.25,26 Taken together, these varied pathomechanisms may provide an understanding of the spectrum of disease manifestation, responsiveness to immunotherapy, and vulnerability of different neuronal cells in EV71.
The prominence of the acute flaccid paralysis or myelitis phenotype in the present cohort appears strikingly similar to recent enterovirus D68 (EVD68) cohorts with longitudinal involvement of spinal gray matter.27 Furthermore, patients with EVD68 also had high rates of residual motor deficits, despite immunomodulatory and antiviral treatments, supporting our observation of the vulnerability of motor pathways. In contrast, patients with EVD68 did not develop neurogenic pulmonary edema or myoclonic jerks, which generally resonates with other motor neuron diseases in which disease-modifying treatment remains to be developed. However, new antiviral agents, such as pocapavir, a capsid binder that has been efficacious for poliovirus, may be beneficial for EV71 treatment.28
At the severe end of the clinical spectrum, all patients with pulmonary edema (which was strongly associated with an adverse clinical outcome) demonstrated restricted diffusion within the dorsal brainstem on MRI. Histopathology correlated with the imaging findings among deaths associated with fulminant disease. These findings support the concept that inflammation may be an important modifiable pathophysiological process12,13,15 and corroborate observations that immunological therapies such as IVIG may be beneficial in EV71 neurological disease.4,5,15,29 Severe EV71 neurological disease has been attributed to a cytokine storm, with increased concentrations of interleukins 1, 6, and 8 and interferon gamma,29-31 promoting inflammation or necrosis and subsequent gliosis.15 Previous retrospective investigations have shown that IVIG therapy dampens interleukin and interferon gamma responses, with consequent favorable outcome in patients with EV71 with neurological disease and autonomic dysfunction.29 Corticosteroids have long been the mainstay of treatment of viral and inflammatory myelitis, despite a lack of robust evidence, and their use has been documented since 2000 in EV71 disease.17,32-34 High-dose corticosteroids have been used with apparent benefit in treating acute flaccid paralysis due to West Nile virus35 and transverse myelitis,32-34,36 as well as in combination with IVIG to treat EV71 with CNS complications and pulmonary edema.31,37 This study was not designed to determine the efficacy of treatment, but high-dose corticosteroid treatment did not appear to have a deleterious effect.
Although CSF testing is usually positive in enterovirus aseptic meningitis, it is frequently negative in EV71-associated neurological disease, including encephalomyelitis.3,17,38-40 The present study established that, despite high rates of CNS involvement, EV71 was infrequently identified from CSF specimens, while throat, stool, or rectal swabs had high diagnostic yields. Viral load in the CSF may be low in contrast to continued viral shedding that occurs from the gastrointestinal tract for several weeks after clinical recovery.38 Consequently, diagnostic assessments should include specimens from multiple sites.
Response to the 2013 EV71 outbreak in Sydney was influenced by the substantial progress in understanding the pathogenesis of EV71 since the previous outbreak at the Sydney Children’s Hospital a decade ago.17 However, variability in clinical practice remained, highlighting the need to further develop evidence-based therapeutic guidelines. Ongoing surveillance remains important in developing awareness and maintaining public health approaches. Heightened awareness led to early introduction of close observation and supportive care. Signs of autonomic involvement (eg, mottled skin, tachypnea, tachycardia, and high blood pressure), limb weakness, or cranial nerve dysfunction were considered potential indicators of severe disease that warranted immunotherapy.
Among patients who received an early diagnosis and initiation of immunotherapy, there were no fatalities, and favorable prognoses were evident in 77% (44 of 57) and 89% (51 of 57) at 2 months’ and 12 months’ follow-up, respectively, suggesting that the present management approach may have altered the natural history of EV71. While the proportion and severity of patients with invasive CNS disease were greatly diminished in the present outbreak compared with previous experiences in Sydney,16,17 the 4 fatalities related to fulminant disease serve as a stark reminder of the severity of EV71.
The present study demonstrates some of the challenges related to determining the effect of immunotherapy in a disease characterized by unpredictable outbreaks, including trial design, use of sensitive and relevant outcome measures, and targeting of specific patient groups for intervention. It may not be feasible to undertake a randomized clinical trial to further investigate the benefits of corticosteroid use and IVIG treatment in EV71 in view of the expense and finite supply of IVIG. However, it is critical to develop therapeutic guidelines, including algorithms for patient stratification, to assist physicians in the clinical management of these patients.
Enterovirus 71 is a potentially fatal and devastating neurotropic virus that may be considered the new polio because of its long-term functional morbidity of focal paresis linked to involvement of gray matter in the brainstem or spinal cord. Our experience suggests that identification of distinct clinicoradiological syndromes using the WHO classification,5 predominantly involving the spinal cord and brainstem, enables rapid recognition of patients with severe disease in developing outbreaks, which may facilitate prompt initiation of supportive and immunological treatment. It is critical to further develop evidence-based therapeutic guidelines incorporating factors related to outcome and potential responsiveness to disease-modifying immunotherapy. Although vaccination will be an important future preventive strategy, children seen with fulminant CNS disease that leads to permanent disability represent a major diagnostic and therapeutic challenge.
Accepted for Publication: November 13, 2015.
Corresponding Author: Hugo Sampaio, FRACP, Department of Neurology, Sydney Children’s Hospital, High Street, Randwick, New South Wales, Australia 2031 (email@example.com).
Published Online: January 19, 2016. doi:10.1001/jamaneurol.2015.4388.
Author Contributions: Dr Teoh had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Drs Farrar and Sampaio contributed equally to this work.
Study concept and design: Teoh, Britton, Kandula, Jones, Andrews, Farrar, Sampaio.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Teoh, Mohammad, Britton, Rawlinson, Andrews, Farrar, Sampaio.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Teoh, Britton, Andrews, Sampaio.
Obtained funding: Booy, Jones.
Administrative, technical, or material support: Teoh, Jones, Ramachandran, Dale, Farrar, Sampaio.
Study supervision: Jones, Rawlinson, Andrews, Dale, Farrar, Sampaio.
Conflict of Interest Disclosures: None reported.
Funding/Support: Dr Teoh received scholarship support from the Thyne Reid Foundation. Dr Britton was supported by scholarship grant 1074547 from the Australian Government National Health and Medical Research Council (NHMRC), The Royal Australasian College of Physicians Paediatrics & Child Health Division, a Child Health NHMRC Award for Excellence, and a Norah Therese-Hayes Dean’s Pediatric Infectious Disease Fellow Award. Drs Booy and Jones are funded by a NHMRC Centre for Research Excellence in Critical Infection.
Role of the Funder/Sponsor: The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.