Hybrid capture shotgun sequencing detected unexpected viruses in the cerebrospinal fluid of children with acute meningitis and encephalitis.

PURPOSE: Investigation of undiagnosed cases of infectious neurological diseases, especially in the paediatric population, remains a challenge. This study aimed to enhance understanding of viruses in CSF from children with clinically diagnosed meningitis and/or encephalitis (M/ME) of unknown aetiology using shotgun sequencing enhanced by hybrid capture (HCSS). METHODS: A single-centre prospective study was conducted at Sant Joan de Déu University Hospital, Barcelona, involving 40 M/ME episodes of unknown aetiology, recruited from May 2021 to July 2022. All participants had previously tested negative with the FilmArray Meningitis/Encephalitis Panel. HCSS was used to detect viral nucleic acid in the patients' CSF. Sequencing was performed on Illumina NovaSeq platform. Raw sequence data were analysed using CZ ID metagenomics and PikaVirus bioinformatics pipelines. RESULTS: Forty episodes of M/ME of unknown aetiology in 39 children were analysed by HCSS. A significant viral detection in 30 CSF samples was obtained, including six parechovirus A, three enterovirus ACD, four polyomavirus 5, three HHV-7, two BKV, one HSV-1, one VZV, two CMV, one EBV, one influenza A virus, one rhinovirus, and 13 HERV-K113 detections. Of these, one sample with BKV, three with HHV-7, one with EBV, and all HERV-K113 were confirmed by specific PCR. The requirement for Intensive Care Unit admission was associated with HCSS detections. CONCLUSION: This study highlights HCSS as a powerful tool for the investigation of undiagnosed cases of M/ME. Data generated must be carefully analysed and reasonable precautions must be taken before establishing association of clinical features with unexpected or novel virus findings.

Metagenomic Next-Generation Sequencing (mNGS) of cerebrospinal fluid for diagnosis of human herpesvirus 6B encephalitis following transplantation for severe aplastic anemia.

INTRODUCTION: Human herpesvirus 6B (HHV-6B) encephalitis is common in immunosuppressed patients and presents a diagnostic challenge for physicians. Metagenomic next-generation sequencing (mNGS) may facilitate early diagnosis of HHV-6B encephalitis. Herein, we described a case of HHV-6B encephalitis following transplantation for severe aplastic anemia (SAA) diagnosed by mNGS. CASE SUMMARY: A 31-year-old male underwent myeloablative haploid hematopoietic stem cell transplantation for the treatment of SAA. On day + 21 after transplantation, the patient developed symptoms such as sudden epilepsy, drowsiness, memory dislocation, and memory loss. HHV-6B encephalitis was confirmed based on cranial MRI and mNGS of cerebrospinal fluid. Following antiviral therapy with sodium foscarnet, the symptoms improved and HHV-6B was negative by mNGS. There were no serious sequelae. Currently, the patient is in good health and is still under follow-up. CONCLUSIONS: A case of HHV-6B encephalitis after SAA transplantation was diagnosed by mNGS of cerebrospinal fluid in time and was effectively treated with sodium foscarnet.

Evolving etiologies, comorbidities, survival, and costs of care in adult encephalitis.

Encephalitis is a central nervous system disorder, often caused by infectious agents or aberrant immune responses. We investigated causes, comorbidities, costs, and outcomes of encephalitis in a population-based cohort. ICD-10 codes corresponding to encephalitis were used to identify health services records for all adults from 2004 to 2019. Data were cross-validated for identified diagnoses based on laboratory confirmation using univariate and multivariate statistical analyses. We identified persons with a diagnosis of encephalitis and abnormal cerebrospinal fluid (CSF) results (n = 581) in whom viral genome was detected (n = 315) in a population of 3.2 million adults from 2004 to 2019. Viral genome-positive CSF samples included HSV-1 (n = 133), VZV (n = 116), HSV-2 (n = 34), enterovirus (n = 4), EBV (n = 5), and CMV (n = 3) with the remaining viruses included JCV (n = 12) and HHV-6 (n = 1). The mean Charlson Comorbidity Index (2.0) and mortality rate (37.6%) were significantly higher in the CSF viral genome-negative encephalitis group although the mean costs of care were significantly higher for the CSF viral genome-positive group. Cumulative incidence rates showed increased CSF VZV detection in persons with encephalitis, which predominated in persons over 65 years with a higher mean Charlson index. We detected HSV-2 and VZV more frequently in CSF from encephalitis cases with greater material-social deprivation. The mean costs of care were significantly greater for HSV-1 encephalitis group. Encephalitis remains an important cause of neurological disability and death with a viral etiology in 54.2% of affected adults accompanied by substantial costs of care and mortality. Virus-associated encephalitis is evolving with increased VZV detection, especially in older persons.

The efficacy of haemoperfusion combined with continuous venovenous haemodiafiltration in the treatment of severe viral encephalitis in children.

BACKGROUND: This study investigated the efficacy of the integrated blood purification mode of early haemoperfusion (HP) combined with continuous venovenous haemodiafiltration (CVVHDF) in children with severe viral encephalitis, and evaluated the correlation of cerebrospinal fluid (CSF) neopterin (NPT) levels with prognosis. METHODS: The records of children with viral encephalitis who received blood purification treatment in the authors' hospital from September 2019 to February 2022 were retrospectively analysed. According to the blood purification treatment mode, they were divided into the experimental group (HP + CVVHDF, 18 cases), control group A (CVVHDF only, 14 cases), and control group B (16 children with mild viral encephalitis who did not receive blood purification treatment). The correlation between the clinical features, severity of the disease and the extent of lesions on brain magnetic resonance imaging (MRI) and the CSF NPT levels was analysed. RESULTS: The experimental group and control group A were comparable with respect to age, gender and hospital course (P > 0.05). There was no significant difference in speech and swallowing functions between the two groups after treatment (P > 0.05) and no significant difference in 7 and 14-day mortality (P > 0.05). The CSF NPT levels in the experimental group before treatment were significantly higher compared with control group B (P < 0.05). The extent of brain MRI lesions correlated positively with CSF NPT levels (P < 0.05). In the experimental group (14 cases), the serum NPT levels decreased after treatment, whereas the CSF NPT levels increased after treatment, and the differences were statistically significant (P < 0.05). Dysphagia and motor dysfunction correlated positively with CSF NPT levels (P < 0.05). CONCLUSION: Early HP combined with CVVHDF in the treatment of severe viral encephalitis in children may be a better approach than CVVHDF only for improving prognosis. Higher CSF NPT levels indicated the likelihood of a more severe brain injury and a greater possibility of residual neurological dysfunction.

Structured Imaging Approach for Viral Encephalitis.

MR imaging is essential in diagnosing viral encephalitis. Clinical features, cerebrospinal fluid analysis and pathogen confirmation by polymerase chain reaction can be supported by assessing imaging features. MR imaging patterns with typical locations can identify pathogens such as temporal lobe for herpes simplex virus type 1; bilateral thalami for Japanese encephalitis and influenza virus ; and brainstem for enterovirus and rabies. In this article, we have reviewed representative viral encephalitis and its MR imaging patterns. In addition, we also presented acute viral encephalitis without typical MR imaging patterns, such as dengue and varicella-zoster virus encephalitis.

Intrathecal Antibody Production Against Epstein-Barr, Herpes Simplex, and Other Neurotropic Viruses in Autoimmune Encephalitis.

BACKGROUND AND OBJECTIVES: Neurotropic viruses are suspected to play a role in the pathogenesis of autoimmune diseases of the CNS such as the association between the Epstein-Barr virus (EBV) and multiple sclerosis (MS). A group of autoimmune encephalitis (AE) is linked to antibodies against neuronal cell surface proteins. Because CNS infection with the herpes simplex virus can trigger anti-NMDA receptor (NMDAR) encephalitis, a similar mechanism for EBV and other neurotropic viruses could be postulated. To investigate for previous viral infections of the CNS, intrathecally produced virus-specific antibody synthesis was determined in patients with AE. METHODS: Antibody-specific indices (AIs) against EBV and measles, rubella, varicella zoster, herpes simplex virus, and cytomegalovirus were determined in 27 patients having AE (anti-NMDAR encephalitis, n = 21, and LGI1 encephalitis, n = 6) and in 2 control groups comprising of 30 patients with MS and 21 patients with noninflammatory CNS diseases (NIND), which were sex and age matched. RESULTS: An intrathecal synthesis of antibodies against EBV was found in 5/27 (19%) patients with AE and 2/30 (7%) of the patients with MS. All these patients had also at least 1 additional elevated virus-specific AI. In contrast, in none of the patients with NIND, an elevated virus-specific AI was detected. DISCUSSION: Intrathecally produced antibodies against EBV can be found in patients with AE and MS but only together with antibodies against different neurotropic viruses. Evidence of these antibodies is the result of a polyspecific immune response similar yet distinct from MS response rather than an elapsed infection of the CNS.

COVID-19 Encephalitis with SARS-CoV-2 Detected in Cerebrospinal Fluid Presenting as a Stroke Mimic.

We report the case of a 35-year-old male with COVID-19 encephalitis presenting as a stroke mimic with sudden-onset expressive and receptive dysphasia, mild confusion and right arm incoordination. The patient received thrombolysis for a suspected ischaemic stroke, but later became febrile and SARS-CoV-2 was detected in cerebrospinal fluid. Electroencephalography demonstrated excess in slow waves, but neuroimaging was reported as normal. Respiratory symptoms were absent throughout and nasopharyngeal swab was negative for SARS-CoV-2. At the most recent follow-up, the patient had made a full neurological recovery. Clinicians should therefore consider testing for SARS-CoV-2 in CSF in patients who present with acute focal neurology, confusion and fever during the pandemic, even when there is no evidence of respiratory infection.

Reduced impact of viral load of HHV-6 in liquor on severity of AESD due to exanthema subitum: A case report and literature review.

BACKGROUND: The most common causative pathogen of acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) was reported as HHV-6. Although excitotoxic injury with delayed neuronal death is considered to be a possible pathogenesis of AESD, the detailed pathophysiology remains unclear. CASE PRESENTATION: We present a twelve-month-old girl with AESD due to HHV-6 primary infection. She was successfully treated for AESD including targeted temperature management and the administration of vitamin B1, B6, and L-carnitine. Although the viral load of HHV-6 in her liquor was high (12,000 copies/mL), she fully recovered without antiviral agent use. DISCUSSION: There has been no study focusing on the HHV-6 viral load in patients with AESD, and only a few case reports have been published. We reviewed the clinical features and viral load in the liquor of our case and four reported infants with AESD due to HHV-6 primary infection who had real-time PCR tests results. Viral loads in the three patients with a poor prognosis were 31.5, negative, and 3,390 copies/mL, respectively. On the other hand, the copy numbers of HHV-6 DNA in the two patients with no sequelae were 12,000 and 106 copies/mL, respectively, and our case had the highest viral load among the five summarized patients.

Procalcitonin measurement using antibody-conjugated fluorescent microspheres distinguishes atypical bacterial meningitis from viral encephalitis in children.

Examination of cerebrospinal fluid in atypical bacterial meningitis (ABM) is similar to that of viral encephalitis (VE), so ABM can easily be misdiagnosed as VE, which can delay diagnosis and treatment. We developed a simple, rapid hand-held lateral flow immunoassay detection system based on fluorescent microspheres (FMS) for procalcitonin (PCT) detection, which provides an indicator to differentiate between ABM and VE. With this novel method, the antigen-antibody reaction systems involve different species, making the test strips more stable than those utilizing one species. The strips exhibited a wide dynamic range (0.04-50 ng/mL) and good sensitivity (0.03 ng/mL). The function of PCT in the identification of ABM and VE in children was further studied. A significant difference in PCT levels was observed between the ABM and VE groups (P = 0.00) and between the ABM and the normal control groups (P = 0.00). PCT levels were not significantly different between the VE and normal control groups (P = 0.30). The area under the receiver operating characteristic curve of PCT for the diagnosis of ABM was 0.95. These findings collectively indicate the usefulness of the PCT detection method based on FMS for clinically differentiating between ABM and VE.

Human Herpesvirus 6 Encephalitis in Immunocompetent and Immunocompromised Hosts.

OBJECTIVE: The aim of this study was to analyze the clinical, radiologic, and biological features associated with human herpesvirus 6 (HHV-6) encephalitis in immunocompetent and immunocompromised hosts to establish which clinical settings should prompt HHV-6 testing. METHODS: We performed a retrospective research in the virology database of Fondazione IRCCS Policlinico San Matteo (Pavia, Italy) for all patients who tested positive for HHV-6 DNA in the CSF and/or in blood from January 2008 to September 2018 and separately assessed the number of patients meeting the criteria for HHV-6 encephalitis in the group of immunocompetent and immunocompromised hosts. RESULTS: Of the 926 patients tested for HHV-6 during the period of interest, 45 met the study criteria. Among immunocompetent hosts (n = 17), HHV-6 encephalitis was diagnosed to 4 infants or children presenting with seizures or mild encephalopathy during primary HHV-6 infection (CSF/blood replication ratio <<1 in all cases). Among immunocompromised hosts (n = 28), HHV-6 encephalitis was diagnosed to 7 adolescents/adults with hematologic conditions presenting with altered mental status (7/7), seizures (3/7), vigilance impairment (3/7), behavioral changes (2/7), hyponatremia (2/7), and anterograde amnesia (1/7). Initial brain MRI was altered only in 2 patients, but 6 of the 7 had a CSF/blood replication ratio >1. CONCLUSIONS: The detection of a CSF/blood replication ratio >1 represented a specific feature of immunocompromised patients with HHV-6 encephalitis and could be of special help to establish a diagnosis of HHV-6 encephalitis in hematopoietic stem cell transplant recipients lacking radiologic evidence of limbic involvement.

Clinical significance of Epstein-Barr virus in the cerebrospinal fluid of immunocompetent patients.

INTRODUCTION: Polymerase chain reaction (PCR)-based testing of cerebrospinal fluid (CSF) samples has greatly facilitated the diagnosis of central nervous system (CNS) infections. However, the clinical significance of Epstein-Barr virus (EBV) DNA in CSF of individuals with suspected CNS infection remains unclear. We wanted to gain a better understanding of EBV as an infectious agent in immunocompetent patients with CNS disorders. METHODS: We identified cases of EBV-associated CNS infections and reviewed their clinical and laboratory characteristics. The study population was drawn from patients with EBV PCR positivity in CSF who visited Pusan National University Hospital between 2010 and 2019. RESULTS: Of the 780 CSF samples examined during the 10-year study period, 42 (5.4 %) were positive for EBV DNA; 9 of the patients (21.4 %) were diagnosed with non-CNS infectious diseases, such as optic neuritis, Guillain-Barré syndrome, and idiopathic intracranial hypotension, and the other 33 cases were classified as CNS infections (22 as encephalitis and 11 as meningitis). Intensive care unit admission (13/33 patients, 39.3 %) and presence of severe neurological sequelae at discharge (8/33 patients, 24.2 %) were relatively frequent. In 10 patients (30.3 %), the following pathogens were detected in CSF in addition to EBV: varicella-zoster virus (n = 3), cytomegalovirus (n = 2), herpes simplex virus 1 (n = 1), herpes simplex virus 2 (n = 1), Streptococcus pneumomiae (n = 2), and Enterococcus faecalis (n = 1). The EBV-only group (n = 23) and the co-infection group (n = 10) did not differ in age, gender, laboratory data, results of brain imaging studies, clinical manifestations, or prognosis; however, the co-infected patients had higher CSF protein levels. CONCLUSION: EBV DNA in CSF is occasionally found in the immunocompetent population; the virus was commonly associated with encephalitis and poor prognosis, and frequently found together with other microbes in CSF.

Cerebrospinal fluid metabolites in tryptophan-kynurenine and nitric oxide pathways: biomarkers for acute neuroinflammation.

AIM: To explore the cerebrospinal fluid (CSF) metabolite features in acute neuroinflammatory diseases and identify potential biomarkers to diagnose and monitor neuroinflammation. METHOD: A cohort of 14 patients (five females, nine males; mean [median] age 7y 9mo [9y], range 6mo-13y) with acute encephalitis (acute disseminated encephalomyelitis n=6, unknown suspected viral encephalitis n=3, enteroviral encephalitis n=2, seronegative autoimmune encephalitis n=2, herpes simplex encephalitis n=1) and age-matched non-inflammatory neurological disease controls (n=14) were investigated using an untargeted metabolomics approach. CSF metabolites were analyzed with liquid chromatography coupled to high resolution mass spectrometry, followed by subsequent multivariate and univariate statistical methods. RESULTS: A total of 35 metabolites could be discriminated statistically between the groups using supervised orthogonal partial least squares discriminant analysis and analysis of variance. The tryptophan-kynurenine pathway contributed nine key metabolites. There was a statistical increase of kynurenine, quinolinic acid, and anthranilic acid in patients with encephalitis, whereas tryptophan, 3-hydroxyanthrnailic acid, and kynurenic acid were decreased. The nitric oxide pathway contributed four metabolites, with elevated asymmetric dimethylarginine and argininosuccinic acid, and decreased arginine and citrulline in patients with encephalitis. An increase in the CSF kynurenine/tryptophan ratio (p<0.001), anthranilic acid/3-hydroxyanthranilic acid ratio (p<0.001), asymmetric dimethylarginine/arginine ratio (p<0.001), and neopterin (p<0.001) strongly predicted neuroinflammation. INTERPRETATION: The combination of alterations in the tryptophan-kynurenine pathway, nitric oxide pathway, and neopterin represent a useful potential panel for neuroinflammation and holds potential for clinical translation practice. WHAT THIS PAPER ADDS: The kynurenine/tryptophan and anthranilic acid/3-hydroxyanthranilic acid ratios hold great potential as biomarkers of neuroinflammation. Elevation of the asymmetric dimethylarginine/arginine ratio in acute brain inflammation shows dysregulation of the nitric oxide pathway.

Prospective case-control study of enterovirus detection differences in children's cerebrospinal fluid between multiplex PCR and real-time RT-PCR assay.

BACKGROUND: Viral encephalitis is common in childhood. It is an acute brain parenchymal inflammation caused by a variety of viral infection, and enterovirus accounts for the majority. Due to atypical clinical manifestations, pathogenic testing is important for assisting clinical diagnosis. The purpose of this study was to evaluate the performance of the multiplex PCR assay compared with quantitative real-time PCR for enterovirus detection. METHODS: A prospective case-control study was performed involving 103 pediatric patients suspected for viral encephalitis and cerebrospinal fluid (CSF) samples were collected and tested for 9 pathogens using multiplex PCR assay during April to November in 2018. In parallel, an aliquot of samples was tested for enterovirus infection by real-time PCR assay. RESULTS: There were 85.4% children were confirmed as viral encephalitis on discharge, the remaining ones were diagnosed as other CNS diseases, such as epilepsy. The specificity of the two methods was the same as that of the clinical diagnosis, but the sensitivity and consistency with clinical diagnosis of multiplex PCR were both higher than the real-time PCR. Besides of enterovirus, multiplex PCR could also detect coinfection of enterovirus with Epstein-Barr virus and mumps virus. CONCLUSION: Results of multiplex PCR method are more consistent with the clinical diagnosis and are superior to real-time PCR for detecting enterovirus in CSF.

Neurological Manifestations of COVID-19 Feature T Cell Exhaustion and Dedifferentiated Monocytes in Cerebrospinal Fluid.

Patients suffering from Coronavirus disease 2019 (COVID-19) can develop neurological sequelae, such as headache and neuroinflammatory or cerebrovascular disease. These conditions-termed here as Neuro-COVID-are more frequent in patients with severe COVID-19. To understand the etiology of these neurological sequelae, we utilized single-cell sequencing and examined the immune cell profiles from the cerebrospinal fluid (CSF) of Neuro-COVID patients compared with patients with non-inflammatory and autoimmune neurological diseases or with viral encephalitis. The CSF of Neuro-COVID patients exhibited an expansion of dedifferentiated monocytes and of exhausted CD4+ T cells. Neuro-COVID CSF leukocytes featured an enriched interferon signature; however, this was less pronounced than in viral encephalitis. Repertoire analysis revealed broad clonal T cell expansion and curtailed interferon response in severe compared with mild Neuro-COVID patients. Collectively, our findings document the CSF immune compartment in Neuro-COVID patients and suggest compromised antiviral responses in this setting.

Cerebrospinal fluid confirmed COVID-19-associated encephalitis treated successfully.

The COVID-19 pandemic that attracted global attention in December 2019 is well known for its clinical picture that is consistent with respiratory symptoms. Currently, the available medical literature describing the neurological complications of COVID-19 is gradually emerging. We hereby describe a case of a 31-year-old COVID-19-positive patient who was admitted on emergency basis. His clinical presentation was primarily neurological, rather than the COVID-19's classical respiratory manifestations. He presented with acute behavioural changes, severe confusion and drowsiness. The cerebrospinal fluid analysis was consistent with COVID-19 encephalitis, as well as the brain imaging. This experience confirms that neurological manifestations might be expected in COVID-19 infections, despite the absence of significant respiratory symptoms. Whenever certain red flags are raised, physicians who are involved in the management of COVID-19 should promptly consider the possibility of encephalitis. Early recognition of COVID-19 encephalitis and timely management may lead to a better outcome.

Acute viral encephalitis associated with human parvovirus B19 infection: unexpectedly diagnosed by metagenomic next-generation sequencing.

We report here a case of a 17-year-old boy with viral encephalitis associated with human parvovirus B19 who presented consciousness disturbance, left hemiparesis, and focal neurologic signs. The diagnosis was based on the specific sequence reads corresponding to human parvovirus B19 (PVB19) in a CSF sample as analyzed by metagenomic next-generation sequencing (mNGS). Thus, PVB19 should be considered in the differential diagnosis of encephalitis and encephalopathy of unknown etiology. The introduction of mNGS into the diagnostic protocol of neuropathies, especially for those undiagnosed, could interrogate all genetic information in a biologic sample and facilitate the identification of the etiological agent.

Pseudorabies virus encephalitis in humans: a case series study.

Pseudorabies virus (PRV) is known to cause severe encephalitis in juvenile pigs and various non-native hosts; recent evidences suggest that PRV might cause encephalitis in humans. In a multicenter cohort study in China, next-generation sequencing of cerebrospinal fluid (CSF) was performed to detect pathogens in all patients with clinically suspected central nervous system infections. This study involved all the patients whose CSF samples were positive for PRV-DNA; their clinical features were evaluated, and species-specific PCR and serological tests were sequentially applied for validation. Among the 472 patients tested from June 1, 2016, to December 1, 2018, six were positive for PRV-DNA, which were partially validated by PCR and serological tests. Additionally, we retrospectively examined another case with similar clinical and neuroimaging appearance and detected the presence of PRV-DNA. These patients had similar clinical manifestations, including a rapid progression of panencephalitis, and similar neuroimaging features of symmetric lesions in the basal ganglia and bilateral hemispheres. Six of the patients were engaged in occupations connected with swine production. PRV infection should be suspected in patients with rapidly progressive panencephalitis and characteristic neuroimaging features, especially with exposure to swine.

Encephalopathy and Encephalitis Associated with Cerebrospinal Fluid Cytokine Alterations and Coronavirus Disease, Atlanta, Georgia, USA, 2020.

There are few detailed investigations of neurologic complications in severe acute respiratory syndrome coronavirus 2 infection. We describe 3 patients with laboratory-confirmed coronavirus disease who had encephalopathy and encephalitis develop. Neuroimaging showed nonenhancing unilateral, bilateral, and midline changes not readily attributable to vascular causes. All 3 patients had increased cerebrospinal fluid (CSF) levels of anti-S1 IgM. One patient who died also had increased levels of anti-envelope protein IgM. CSF analysis also showed markedly increased levels of interleukin (IL)-6, IL-8, and IL-10, but severe acute respiratory syndrome coronavirus 2 was not identified in any CSF sample. These changes provide evidence of CSF periinfectious/postinfectious inflammatory changes during coronavirus disease with neurologic complications.

Parechovirus-A3 encephalitis presenting with focal seizure mimicking herpes simplex virus infection.

BACKGROUND: Febrile neonates and young infants presenting with seizure require immediate evaluation and treatment. Herein we experienced two young infants with parechovirus-A3 (PeV-A3) encephalitis, initially presented with focal seizure suspecting herpes simplex virus (HSV) encephalitis. CASES: We have experienced 2 infantile cases, initially presented with focal seizure. At presentation, HSV encephalitis was strongly suspected and empiric acyclovir therapy was started; however, serum and/or cerebrospinal fluid (CSF) PCR for HSV were negative. Instead, serum and/or CSF PCR for parechovirus-A was positive. PeV-A3 infection was confirmed by genetic sequence analyses. Both cases required multiple anticonvulsant therapy and intensive care for intractable seizure. Diffusion-weighted imaging of brain magnetic resonance imaging (MRI) showed distinct findings; high-intensity lesions in the gray matter of parietal and occipital lobes in Case 1, and bilateral decreased diffusion of the deep white matter and corpus callosum in Case 2. We have followed two cases more than four years; Case 1 developed epilepsy, has been on an anticonvulsant to control her seizure. Case 2 has significant neurodevelopmental delay, unable to stand or communicate with language. CONCLUSIONS: PeV-A3 encephalitis needs to be in differential diagnosis when neonates and young infants present with focal seizure, mimicking HSV encephalitis. Special attention may be necessary in patients with PeV-A3 encephalitis given it could present with intractable seizure with high morbidity in a long-term.