Incidence, aetiology, and sequelae of viral meningitis in UK adults: a multicentre prospective observational cohort study

Aetiologies, neuroradiological features, and risk factors for mortality and long-term neurosequelae of febrile coma in Malawian children: a prospective cohort study

BACKGROUND

Children in febrile coma in Africa are frequently hospitalised, with poorer outcomes than those in high-income settings. Cerebral malaria is historically the most common cause of febrile coma. Due to limited diagnostic and radiological resources and a decrease in malaria prevalence, there might be under-recognition of non-malarial coma. However, prospective data are scarce. We aimed to determine causes, neuroradiological features, risk factors for mortality, and neurosequelae of children in febrile coma in Malawi.

METHODS

In this prospective cohort study, we enrolled children in a coma (Blantyre Coma Scale score ≤2) who were aged between 3 months and 15 years at Queen Elizabeth Central Hospital, Blantyre, Malawi. We used pathogen-specific PCR analysis of blood and cerebrospinal fluid for 15 pathogens including Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, Salmonella spp, non-typhoidal Salmonella, Salmonella enterica serotype Typhi (S Typhi), Klebsiella spp, Escherichia coli, Mycobacterium tuberculosis (also using GeneXpert), Streptococcus agalactiae, herpes simplex virus (types 1 and 2), varicella zoster virus, cytomegalovirus, enteroviruses, and SARS-CoV-2; microscopy for malaria; admission brain MRI to enhance the diagnosis of cause and identify brain injury, swelling, and any other complications; and electroencephalography tracings were used identify subclinical seizures or non-convulsive status epilepticus. Assessment of malarial retinopathy was performed by a trained ophthalmologist. We used regression models to estimate risk factors for (and the difference in) 30-day mortality and 180-day neurosequelae (outcome assessed in-person) between children with non-malarial coma and cerebral malaria.

FINDINGS

Between Jan 31, 2018, and June 30, 2021, we recruited 352 children with febrile coma. Cerebral malaria was the most common cause (in 231 [66%] of 352 children). Pathogenic diagnosis was possible in 289 (82%) of 352 children. Co-infection was identified in 63 (27%) of 231 children with cerebral malaria, of which 49 (78%) were bacterial. The most common non-malarial causes of coma were meningitis (48 [14%] of 352 children) and encephalitis (24 [7%] of 352); 32 (9%) cases had an unknown cause. Compared with standard cultures, PCR significantly increased pathogen diagnosis (p<0·0001), with the highest yield in patients with meningitis (seven [15%] of 48 vs 30 [63%] of 48). S pneumoniae (n=44) and non-typhoidal salmonella or S Typhi (n=24) were the most frequently detected bacterial pathogens. Brain parenchymal abnormalities were identified on MRI in most children with febrile coma (165 [92%] of 178), and were significantly more common in children with non-malarial coma (68 [100%] of 68]) than cerebral malaria (98 [89%] of 110; p<0·0001). Overall, at 30 days after discharge, death (69 [21%] of 323) or any neurological impairment (163 [50%] of 323) were common, but poorer long-term outcomes were more frequent following non-malarial coma than cerebral malaria (death at 30 days: 32 [28%] of 114 vs 37 [18%] of 209, p=0·029; severe neurological impairment at 180 days: 19 [17%] of 114 vs 15 [7%] of 209, p=0·0079). Children who had cerebral malaria with CNS co-infection had higher mortality (ten [37%] of 27) than those with cerebral malaria alone (19 [12%] of 154, p=0·0033).

INTERPRETATION

Despite malaria control efforts, cerebral malaria remains the most common cause of febrile coma in Malawi. However, non-malarial coma causes a greater disease burden (death and disability), and a higher case-fatality rate was observed in non-malarial coma and cerebral malaria with non-malarial co-infection than cerebral malaria alone. To adequately treat severe invasive bacterial infections, that are frequently not detected in routine clinical practice, commencing empirical antimicrobials in all children in febrile coma, including those with cerebral malaria, could and should be rapidly implemented across Africa and must be considered. The study highlights the value of molecular diagnostics and imaging to guide diagnosis. The frequent findings of brain abnormalities from imaging at admission emphasises the need for earlier escalation of children with febrile coma to specialist care. Further work is needed to develop feasible molecular and radiological diagnostics for their successful deployment across the continent. Implementation of these methods could improve diagnosis and outcomes for children with febrile coma in Africa.

FUNDING

Wellcome Trust TRANSLATIONS: For the Chichewa, French and Portuguese translations of the abstract see Supplementary Materials section.

Corticosteroids for viral central nervous system infections

PURPOSE OF REVIEW

Viruses are frequent causes of central nervous system (CNS) infection. Lacking specific antiviral treatment or inadequate clinical response may lead to treatment with corticosteroids. This review describes the rationale for and clinical experience with the use of adjunctive corticosteroids for viral CNS infections.

RECENT FINDINGS

Corticosteroids display anti-inflammatory, immunosuppressive, antiproliferative, and vasoconstrictive effects by genomic and nongenomic regulation of human cells. Recent population-based studies consistently show that empiric dexamethasone during diagnostic work-up for meningitis has neither been associated with improved outcome nor adverse effects in viral meningitis. Myelitis is most often due to noninfectious causes and standard empiric treatment includes high-dose methylprednisolone. There are no convincing data on viral myelitis to support a change of this approach. Corticosteroids have occasionally been employed in different types of viral encephalitis. Observational data and a few randomized clinical trials have not documented any substantial beneficial effects of adjunctive corticosteroids in viral encephalitis. Risks of harm with current treatment regimens remained low in published studies.

SUMMARY

Except for myelitis, there are no data to support routine use of corticosteroids for viral CNS infections. Large, multidisciplinary syndromic platform trials of all-cause encephalitis may be a viable way to inform treatment guidelines.

Ability to return to work and persistent symptoms six months after viral meningitis - a retrospective single-centre cohort study

BACKGROUND

Viral meningitis (VM) is often perceived as mild and self-limiting, but some studies indicate reduced ability to work and cognitive sequelae post-infection.

OBJECTIVES

To investigate VM patients' self-reported return to work, persistent symptoms, and social limitations up to 6 months post-hospitalisation, assess predictors for full return to work at 6 months, and quantify neuropsychological testing use.

METHODS

Retrospective single-centre cohort study of VM patients from 2015 to 2020. Data collected covered hospitalisation, work status at admission, Glasgow Outcome Scale (GOS) score at discharge and neuropsychological testing. Additionally, information on work status and persistent symptoms (headaches, concentration difficulty, social limitations and sound sensitivity) at 1-, 3- and 6-month follow-up appointments.

RESULTS

In total, 246 patients were included in the study (median age 33 years, 51.6% female). In all, 26.0% of patients underwent neuropsychological testing. Persistent symptoms could be assessed in 223 patients at follow-up appointments. Headaches were most reported symptom, occurring in 55.6%, 37.7% and 27.8% of patients at 1, 3 and 6 months, respectively. Work status could be assessed in 199 patients. At 6 months, 52.8%patients were fully returned to work, while 24.1% reported a phased or no return. Full return to work was associated with male sex (OR 4.19, p = 0.003) and GOS score 5 at discharge (OR 15.11, p < 0.001).

CONCLUSION

Six months post-VM, approximately 25% of patients had reduced/no work ability and 30% at least one persistent symptom. Women had increased risk of not returning to full work.

Clinical features and risk factors for Epstein-Barr virus-associated encephalitis: a retrospective cohort study

BACKGROUND

Epstein-Barr virus (EBV) has been gradually recognized as an important pathogen of encephalitis, but our knowledge of EBV-associated encephalitis is still limited. The aim of this study was to describe the clinical features and explore the risk factors for EBV-associated encephalitis in a large cohort of Chinese patients.

METHODS

All patients with confirmed encephalitis in our center from June 2020 to April 2021 were enrolled. Data were extracted from the electronic medical record system and analyzed by Student's t test, Mann-Whitney U test, chi-square test, and logistic regression analyses.

RESULTS

This study included a total of 364 patients diagnosed with encephalitis, among which 86 cases (23.6%) had EBV detected in their cerebrospinal fluid (CSF), and 39 cases were diagnosed with EBV-associated encephalitis. The clinical characteristics of EBV-associated encephalitis differ from those caused by other herpes viruses. Compared to other herpes virus-related encephalitis, patients with EBV encephalitis exhibited significantly higher protein levels (1.310 [0.695, 1.840] vs. 0.710 [0.490, 1.700], p < 0.001), lower glucose levels (3.030 [2.585, 3.640] vs. 3.380 [2.990, 4.030], p < 0.001), and a higher incidence of meningeal involvement on MRI (11 (30.6%) vs. 3 (6.5%), p = 0.010). Additionally, univariate logistic regression analysis revealed that age (OR = 1.015, 95% CI: 1.002-1.029), HIV infection (OR = 4.285, 95% CI: 1.582-11.816), non-tumor immunosuppression (OR = 5.713, 95% CI: 1.588-22.883), and peripheral blood EBV infection (OR = 10.204, 95% CI: 4.231-26.346) were independent risk factors for CNS EBV infection.

CONCLUSION

Compared to other herpes virus-associated encephalitis, EBV encephalitis is characterized by a higher degree of meningeal involvement, elevated CSF protein levels, lower glucose levels, and a reduced T-lymphocyte count in peripheral blood. These characteristics suggest that EBV encephalitis may have a distinct pathophysiology.

Varicella-Zoster Virus Meningitis With Hypoglycorrhachia Mimicking Tuberculous Meningitis: A Case Report

Varicella-Zoster virus (VZV) meningitis poses diagnostic challenges and often presents with atypical clinical and laboratory findings. We present a case of VZV meningitis with hypoglycorrhachia mimicking tuberculous meningitis (TBM). A 65-year-old Japanese woman with a past history of successfully treated tuberculosis presented with a persistent headache. Cerebrospinal fluid (CSF) analysis showed lymphocytic pleocytosis and hypoglycorrhachia (CSF glucose: 43 mg/dL, CSF-to-serum glucose ratio: 0.34) with borderline elevated adenosine deaminase ADA level (9.1 IU/L), raising concern for TBM. Head computed tomography (CT) was unremarkable, and chest CT showed only calcified nodules consistent with prior tuberculous infection. The patient met the criteria for possible TBM based on clinical and CSF findings. Empirical treatment with broad-spectrum antibiotics and dexamethasone was initiated for suspected bacterial meningitis. Her symptoms improved rapidly, and both CSF and blood cultures were negative. A multiplex polymerase chain reaction (PCR) test later identified VZV as the causative pathogen. Antiviral therapy was withheld, as the patient's symptoms had fully resolved by the time of diagnosis. She remained well thereafter, with no complications during follow-up. This case illustrates how VZV meningitis can mimic TBM through marked hypoglycorrhachia and a remote history of tuberculosis.

A multifaceted intervention to improve diagnosis and early management of hospitalised patients with suspected acute brain infections in Brazil, India, and Malawi: an international multicentre intervention study

BACKGROUND

Brain infections pose substantial challenges in diagnosis and management and carry high mortality and morbidity, especially in low-income and middle-income countries. We aimed to improve the diagnosis and early management of patients admitted to hospital (adults aged 16 years and older and children aged >28 days) with suspected acute brain infections at 13 hospitals in Brazil, India, and Malawi.

METHODS

With hospital stakeholders, policy makers, and patient and public representatives, we co-designed a multifaceted clinical and laboratory intervention, informed by an evaluation of routine practice. The intervention, tailored for each setting, included a diagnostic and management algorithm, a lumbar puncture pack, a testing panel, and staff training. We used multivariable logistic regression and interrupted time series analysis to compare the coprimary outcomes-the percentage of patients achieving a syndromic diagnosis and the percentage achieving a microbiological diagnosis before and after the intervention. The study was registered at ClinicalTrials.gov (NCT04190303) and is complete.

FINDINGS

Between Jan 5, 2021, and Nov 30, 2022, we screened 10 462 patients and enrolled a total of 2233 patients at 13 hospital sites connected to the four study centres in Brazil, India, and Malawi. 1376 (62%) were recruited before the intervention and 857 (38%) were recruited after the intervention. 2154 patients (96%) had assessment of the primary outcome (1330 [62%] patients recruited pre-intervention and 824 [38%] recruited post-intervention). The median age across centres was 23 years (IQR 6-44), with 1276 (59%) being adults aged 16 years or older and 888 (41%) children aged between 29 days and 15 years; 1264 (59%) patients were male and 890 (41%) were female. Data on race and ethnicity were not recorded. 1020 (77%) of 1320 patients received a syndromic diagnosis before the intervention, rising to 701 (86%) of 813 after the intervention (adjusted odds ratio [aOR] 1·81 [95% CI 1·40-2·34]; p<0·0001). A microbiological diagnosis was made in 294 (22%) of 1330 patients pre-intervention, increasing to 250 (30%) of 824 patients post-intervention (aOR 1·46 [95% CI 1·18-1·79]; p=0·00040). Interrupted time series analysis confirmed that these increases exceeded a modest underlying trend of improvement over time. The percentage receiving a lumbar puncture, time to appropriate therapy, and functional outcome also improved.

INTERPRETATION

Diagnosis and management of patients with suspected acute brain infections improved following introduction of a simple intervention package across a diverse range of hospitals on three continents. The intervention is now being implemented in other settings as part of the WHO Meningitis Roadmap and encephalitis control initiatives.

FUNDING

UK National Institute for Health and Care Research.

Retrospective Analysis of Blood Biomarkers of Neurological Injury in Human Cases of Viral Infection and Bacterial Sepsis

BACKGROUND

Blood biomarkers of neurological injury could provide a rapid diagnosis of central nervous system injury caused by infections. A Food and Drug Administration (FDA)-approved assay for mild traumatic brain injury (TBI) measures glial fibrillary acidic protein (GFAP) and ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), which signal astrocyte and neuronal injury, respectively. Here, we assessed the applicability of this biomarker assay for determining infection-induced brain injury.

METHODS

We measured serum levels of GFAP and UCH-L1 retrospectively in serum samples from 3 study populations: (1) human cases infected with Venezuelan equine encephalitis virus (VEEV) and Madariaga virus (MADV) (n = 73), (2) human sepsis patients who were severely ill or diagnosed with encephalitis (n = 66), and (3) sepsis cases that were subsequently evaluated for cognitive impairment (n = 64).

RESULTS

In the virus infection group, we found elevated GFAP for VEEV (P = .014) and MADV (P = .011) infections, which correlated with seizures (P = .006). In the bacterial sepsis group, GFAP was elevated in cases diagnosed with encephalitis (P = .0007) and correlated with headaches (P = .0002). In the bacterial sepsis cases with a later cognitive assessment, elevated GFAP (P = .0057) at study enrollment was associated with cognitive impairment 6 months later with a positive prognostic capacity of 79% (95% confidence interval, 66%-95%; P = .0068).

CONCLUSIONS

GFAP and UCH-L1 levels measured using an FDA-approved assay for TBI may indicate brain injury resulting from viral or bacterial infections and could predict the development of neurological sequelae.

Herpes simplex-2 meningitis presenting with headache in pregnancy

Herpes simplex virus (HSV) is a double-stranded DNA virus, whose primary target is epithelial cells. It is disseminated by hematogenous spread. HSV type 2 (HSV-2) usually causes genital infection with mucocutaneous lesions or it may be asymptomatic. HSV-2 is also an important cause of meningitis either during primary infection or by (recurrent) reactivation of dormant virus within the central nervous system. The authors present the case of a nulliparous woman in her mid-20s presenting to the emergency department at 22 weeks' gestation with acute onset of headache. CT of the head and magnetic resonance angiography (MRA) were unremarkable. She received broad-spectrum antimicrobial therapy for suspected meningitis. Her cerebrospinal fluid culture detected HSV-2. She denied a history of oral or genital herpes. She commenced treatment with intravenous acyclovir 10 mg/kg 8 hourly for 7 days. She responded clinically and her headache resolved. There remains a relative dearth of cases of HSV-2 meningitis reported in the literature hence making pregnancy management and delivery planning challenging for obstetricians. This case demonstrates the importance of the multidisciplinary team involvement of genitourinary medicine and sexual health physicians, obstetricians and neonatologists with formal documentation of a birth and postnatal care plan.

Unraveling the interplay between meningitis and mitochondria: Etiology, pathogenesis, and therapeutic insights

Meningitis, characterized by an inflammatory response affecting the membranes surrounding the brain and spinal cord, poses a formidable challenge to global public health. Its etiology spans a spectrum of infectious agents, ranging from bacteria, to viruses, fungi, and parasites. Concurrently, mitochondria-traditionally known as 'cellular powerhouses'-have emerged as critical players in various essential biological functions, including but not limited to, energy production, metabolic regulation, and cell fate determination. Emerging evidence suggests that mitochondria may play vital roles in the pathogenesis of meningitis. In this review, we delineated the definition, classification, etiology, pathogenesis, and clinical manifestations of meningitis, and elucidated the structure, dynamics and functions of mitochondria. We subsequently delved into the intricate interplay between meningitis and mitochondria, identifying potential therapeutic interventions targeting mitochondria for the first time. With clinical trials on the horizon, our review lays the foundation for a transformative era in meningitis therapeutics, where unraveling the intricate interplay between meningitis and mitochondria offers promise for mitigating neuroinflammation and improving patient outcomes.

A Multiplex Polymerase Chain Reaction Assay for the Detection of Herpes Simplex Virus, Cytomegalovirus, and Varicella-Zoster Virus in Cerebrospinal Fluid

Viral meningitis poses a significant clinical challenge due to its rapid onset and potential progression to life-threatening encephalitis. Early detection of treatable viral pathogens such as Herpes simplex virus (HSV), Cytomegalovirus (CMV), and Varicella-zoster virus (VZV) is essential for initiating appropriate therapies. However, multiplex PCRs for the rapid and simultaneous detection of these pathogens are scarce due to the complex PCR design and the elaborate validation process using cerebrospinal fluid samples. In this study, we established and validated a novel multiplex PCR assay for detecting HSV, CMV, and VZV in cerebrospinal fluid samples and implemented the assay on a fully automated platform.

Cost-effectiveness of cenobamate as a therapeutic alternative for the treatment of focal epilepsy in adults with inadequate seizure control

Introduction

This study assesses the cost-effectiveness of cenobamate relative to brivaracetam, lacosamide, eslicarbazepine acetate, and perampanel in the management of focal onset seizures (FOS). The objective is to determine whether cenobamate offers enhanced therapeutic benefits and economic viability.

Methods

A comprehensive cost-effectiveness analysis was performed using a lifetime horizon model that encompassed drug acquisition costs, background therapy, monitoring, and seizure management expenses. The incremental cost-effectiveness ratio (ICER) was calculated to evaluate the quality-adjusted life years (QALYs) gained from cenobamate compared to its alternatives.

Results

Findings revealed that cenobamate while incurring slightly higher initial acquisition costs, leads to significant cost offsets due to reductions in overall seizure management expenses and minimized reliance on subsequent anti-seizure medications (ASMs). Additionally, cenobamate significantly enhances patient quality of life, demonstrated by superior response rates (seizure reduction >50%) and remission rates (100% seizure reduction) compared to the analyzed comparators. The cost-effectiveness analysis established that cenobamate is dominant across all evaluated treatment options, achieving greater QALYs at a lower total cost.

Conclusion

Cenobamate represents a more effective and economically advantageous treatment for patients with FOS when compared to brivaracetam, lacosamide, eslicarbazepine acetate, and perampanel. Its capacity to improve seizure control and enhance the quality of life, alongside favorable economic implications, underscores its position as the preferred therapeutic option in this patient population.

Dexamethasone in adults with viral meningitis: an observational cohort study

OBJECTIVES

To investigate whether there is a dose-dependent association between empiric dexamethasone and outcome in viral meningitis.

METHODS

Observational cohort study of adults hospitalized for viral meningitis, both with and without a microbiologically confirmed diagnosis, in Denmark between 2015 and 2020. Dose-dependent associations between dexamethasone (one dose = 10 mg) and an unfavourable outcome (Glasgow Outcome Scale score 1-4) at 30 days after discharge were assessed using weighted logistic regression. Entropy balancing was used to compute weights.

RESULTS

Of 1025 included patients, 658 (64%) did not receive dexamethasone, 115 (11%) received 1-2 doses, 131 (13%) received 3-4 doses, and 121 (12%) received ≥5 doses. Among patients treated with dexamethasone, the median number of doses was higher for those without an identified pathogen than for those with a microbiologically confirmed viral aetiology (5 [interquartile range (IQR) 3-8] vs. 3 [IQR 2-5]; p < 0.001). Using no doses of dexamethasone as a reference, the weighted OR for an unfavourable outcome were 0.55 (95% CI, 0.29-1.07) for 1-2 doses, 1.13 (95% CI, 0.67-1.89) for 3-4 doses, and 1.43 (95% CI, 0.77-2.64) for ≥5 doses. In the subgroup of enteroviral meningitis, the weighted OR was 3.08 (95% CI, 1.36-6.94) for ≥5 doses, but decreased to 2.35 (95% CI, 0.65-8.40) when the reference group was restricted to patients treated with antibiotics for suspected bacterial meningitis.

DISCUSSION

This study showed no dose-dependent association between dexamethasone and an unfavourable outcome in patients with viral meningitis. In enteroviral meningitis, ≥5 doses were associated with an increased risk of an unfavourable outcome. However, sensitivity analysis indicated that the association was affected by unmeasured or residual confounding by severity.

Molecular diagnostics in cerebrospinal fluid for the diagnosis of central nervous system infections

SUMMARYCentral nervous system (CNS) infections can be caused by various pathogens, including bacteria, viruses, fungi, and parasites. Molecular diagnostic methods are pivotal for identifying the different causative pathogens of these infections in clinical settings. The efficacy and specificity of these methods can vary per pathogen involved, and in a substantial part of patients, no pathogen is identified in the cerebrospinal fluid (CSF). Over recent decades, various molecular methodologies have been developed and applied to patients with CNS infections. This review provides an overview of the accuracy of nucleic acid amplification methods in CSF for a diverse range of pathogens, examines the potential value of multiplex PCR panels, and explores the broad-range bacterial and fungal PCR/sequencing panels. In addition, it evaluates innovative molecular approaches to enhance the diagnosis of CNS infections.

Enhanced pathogen identification among patients with clinically suspected meningitis

Background

Delayed or incorrect treatment of meningitis may result in adverse patient outcomes. However, laboratory testing in resource-limited settings is often limited to conventional diagnostic methods. We explored the utility of syndromic molecular assays for diagnosis.

Objectives

We tested cerebrospinal fluid (CSF) specimens collected from patients with clinically suspected meningitis submitted to a tertiary hospital laboratory in January 2021 - May 2021. Primary microbiological analysis (culture, Gram stain and cytochemical analysis) was performed as part of routine testing.

Method

Residual CSF specimens were tested using a bacterial triplex real-time polymerase chain reaction (PCR) assay and a syndromic multi-pathogen real-time PCR assay for the detection of up to 18 bacterial and viral pathogens. Pathogen detection was compared between conventional and molecular assays.

Results

A potential pathogen was detected in 6% (12/188) and 47% (89/188) of specimens on the triplex and the multi-pathogen assay, respectively. Epstein-Barr virus (49/188; 26%), human herpes virus 7 (22/188; 12%), herpes simplex virus 1 (13/188; 7%) and Streptococcus pneumoniae (10/188; 5%) were the leading pathogens detected on the syndromic multi-pathogen PCR. Further, using the multi-pathogen PCR assay, a potential pathogen was detected in 44% (73/166) of the specimens which were negative following routine testing. Overall, combining routine testing and molecular platforms significantly improved pathogen detection (p < 0.001); a potential pathogen was identified in 51% (95/188) of the specimens tested, compared to 12% (22/188) using routine methods alone.

Conclusion

The use of molecular tests improved pathogen detection by 39% when paired with routine methods.

Contribution

Multi-pathogen molecular testing is useful for rapidly diagnosing meningitis cases.

Viral Etiology of Aseptic Meningitis and Clinical Prediction of Herpes Simplex Virus Type 2 Meningitis

BACKGROUND

Aseptic meningitis comprises meningeal inflammation and cerebrospinal fluid (CSF) pleocytosis without positive Gram stain and culture. Regional differences exist in the prevalence of viral etiologies of aseptic meningitis. We aimed to assess the etiologies of aseptic meningitis in immunocompetent adults, focusing on herpes simplex virus type 2 (HSV-2).

METHODS

This study retrospectively analyzed immunocompetent adults diagnosed with meningitis at a Korean tertiary care hospital from 2016 to 2018. Aseptic meningitis was defined through clinical and CSF analysis. We compared clinical and laboratory characteristics across viral etiologies and investigated predictors of HSV-2 meningitis.

RESULTS

A total of 98 patients (46.9% female) with aseptic meningitis were finally enrolled. The etiologies of aseptic meningitis were identified in 62 patients (63.3%), including enterovirus (28.5%), HSV-2 (16.3%), and varicella zoster virus (VZV, 15.3%). HSV-2 showed female predominance, with shorter admission times with longer hospital stays and a recurrent meningitis history. Compared to other viral etiologies, HSV-2 showed higher CSF white blood cell (WBC) counts and protein levels but lower C-reactive protein (CRP) levels. A random forest model identified previous meningitis history and serum CRP level as key predictors of HSV-2 meningitis.

CONCLUSIONS

This study provides insights into the etiologies of aseptic meningitis in a specific Korean region, identifying HSV-2 as a notable cause. The prediction model suggested that the clinical history of previous meningitis and serum CRP level may guide clinical assessment of meningitis.

The Clinical Manifestations, Risk Factors, Etiologies, and Outcomes of Adult Patients with Infectious Meningitis and Encephalitis: Single Center Experience

(1) Background: Central nervous system (CNS) infections, including meningitis and encephalitis, are serious conditions which are associated with high morbidity and mortality. This study aims to identify the clinical manifestations, etiologies, and outcomes of meningitis and encephalitis in adult patients in Saudi Arabia, addressing the current gap in understanding these conditions within this population. (2) Methods: This is a single-center retrospective study which included all adult patients diagnosed with meningitis and encephalitis from March 2016 to May 2022. (3) Results: This study found that most cases of meningitis and encephalitis occurred due to unknown pathogens. Pretreatment with antibiotics prior to lumbar puncture (LP) was found in 71.2% of patients with meningitis. Altered mental status and seizures were common presenting symptoms among patients with encephalitis while altered mental status and fever were common among patients with meningitis. (4) Conclusions: Adherence to guidelines in treating meningitis and encephalitis and performing LPs in a timely manner are important. Establishing national biobanks with biological samples from patients suspected of having meningitis or encephalitis will significantly enhance our understanding of these conditions in Saudi Arabia.

Biomarkers and genotypes in patients with Central nervous system infection caused by enterovirus

PURPOSE

Enteroviruses (EV) comprises many different types and are the most common cause of aseptic meningitis. How the virus affects the brain including potential differences between types are largely unknown. Measuring biomarkers in CSF is a tool to estimate brain damage caused by CNS infections.

METHODS

A retrospective study was performed in samples from 38 patients with acute neurological manifestations and positive CSF-EV RNA (n = 37) or serum-IgM (n = 1). The EV in 17 samples were typed by sequencing. The biomarkers neurofilament light (NFL), glial fibrillary acidic protein (GFAP), S-100B protein, amyloid-β (Aβ) 40 and Aβ42, total-tau (T-tau) and phosphorylated tau (P-tau) were measured and compared with data derived from a control group (n = 19).

RESULTS

There were no increased levels of GFAP (p ≤ 0.1) nor NFL (p ≤ 0.1) in the CSF of patients with EV meningitis (n = 38) compared with controls. However, we found decreased levels of Aβ42 (p < 0.001), Aβ40 (p < 0.001), T-tau (p ≥ 0.01), P-tau (p ≤ 0.001) and S-100B (p ≤ 0.001). E30 (n = 9) and CVB5 (n = 6) were the most frequent EV-types identified, but no differences in biomarker levels or other clinical parameters were found between the infecting virus type. Seven patients who were followed for longer than one month reported remaining cognitive impairment, although no correlations with biomarker concentrations were observed.

CONCLUSION

There are no indication of neuronal or astrocyte damage in patients with EV meningitis. Yet, decreased concentrations of Aβ40, Aβ42, P-tau and T-tau were shown, a finding of unknown importance. Cognitive impairment after acute disease occurs, but with only a limited number of patients analysed, no conclusion can be drawn concerning any association with biomarker levels or EV types.

Metagenomic next-generation sequencing of cerebrospinal fluid reveals etiological and microbiological features in patients with various central nervous system infections

The application of metagenomic next-generation sequencing (mNGS) in pathogens detection of cerebrospinal fluid (CSF) is limited because clinical, microbiological, and biological information are not well connected. We analyzed the 428 enrolled patients' clinical features, pathogens diagnostic efficiency of mNGS in CSF, microbial community structure and composition in CSF, and correlation of microbial and clinical biomarkers in CSF. General characteristics were unspecific but helpful in formulating a differential diagnosis. CSF mNGS has a higher detection rate (34.6%) compared to traditional methods (5.4%). mNGS detection rate was higher when the time from onset to CSF collection was ≤20 days, the CSF leukocytes count was >200 × 106/L, the CSF protein concentration was >1.3 g/L, or CSF glucose concentration was ≤2.5 mmol/L in non-postoperative bacterial CNS infections (CNSi). CSF was not strictly a sterile environment, and the potential pathogens may contribute to the dysbiosis of CSF microbiome. Furthermore, clinical biomarkers were significantly relevant to CNS pathogens. Clinical data are helpful in choosing a proper opportunity to obtain an accurate result of mNGS, and can speculate whether the mNGS results are correct or not. Our study is a pioneering study exploring the CSF microbiome in different CNSIs.

Long-term sequelae after viral meningitis and meningoencephalitis are frequent, even in mildly affected patients, a prospective observational study

Introduction

An increasing number of studies demonstrate that viral meningitis and meningoencephalitis, even those with a mild course of meningitis, can result in residual sequelae.

Methods

We aimed to investigate the long-term outcome in both viral meningitis and meningoencephalitis/encephalitis patients and impact of long-term sequelae on patients' social and professional daily lives in a prospective observational study with a follow-up period of 20 months.

Results

A total of 50 patients (12% encephalitis, 58% meningoencephalitis and 30% meningitis) and 21 control persons participated in the study. The most common cause was the tick-borne encephalitis (TBE) virus. The most important persistent signs and symptoms after 2 years were subjective cognitive impairment (36%), fatigue and/or excessive daytime sleepiness (31%), disturbed nighttime sleep (31%) and headaches (13%), as well as feeling more rapidly exhausted after cognitive effort (53%). Independent of disease severity in the acute phase, almost one third of patients still reported mildly impaired social and/or professional life due to the long-term sequelae, with scores in the health status assessment still significantly lower compared to healthy controls.

Discussion

Regardless of the severity of the acute illness and despite constant improvement within 2 years, 67% of patients still had persistent signs and symptoms, but these were only relevant to everyday social or professional life in about 30% of these patients.

New Insights Into the Therapeutic Management of Varicella Zoster Virus Meningitis: A Series of 123 Polymerase Chain Reaction-Confirmed Cases

Background

Varicella zoster virus (VZV) can reactivate and cause meningitis, but few studies have distinguished it from meningoencephalitis regarding treatment recommendations.The objective of this study was to assess the outcomes of a large series of patients with VZV meningitis according to their therapeutic management.

Methods

We conducted a bicentric retrospective cohort study, in Paris, France, including all adult patients with a cerebrospinal fluid sample positive for VZV by polymerase chain reaction between April 2014 and June 2022. We distinguished meningitis from encephalitis according to the International Encephalitis Consortium criteria. Unfavorable outcome was defined as mortality or functional sequelae defined by a loss of 2 points on the modified Rankin Scale.

Results

We included 123 patients with meningitis. Among them, 14% received no antivirals, while 20% were treated with oral valacyclovir alone, 41% with a short course of intravenous (IV) acyclovir before switch to valacyclovir, and 25% with a long course of IV acyclovir. Outcomes were favorable regardless of antiviral regimen. In multivariate analysis, only age, underlying immunosuppression, and cranial radiculitis appear to be predictive factors for longer IV therapy, based on the Akaike information criterion.

Conclusions

In this study, patients with VZV meningitis had a good outcome, with no evidence of any impact of the treatment strategy. However, further studies are needed to support the possibility of milder treatment in immunocompetent patients, avoiding cost and side effects of IV acyclovir.

Clinical presentation, management, and outcome of suspected central nervous system infections in Indonesia: a prospective cohort study

BACKGROUND

Little is known about the etiology, clinical presentation, management, and outcome of central nervous system (CNS) infections in Indonesia, a country with a high burden of infectious diseases and a rising prevalence of HIV.

METHODS

We included adult patients with suspected CNS infections at two referral hospitals in a prospective cohort between April 2019 and December 2021. Clinical, laboratory, and radiological assessments were standardized. We recorded initial and final diagnoses, treatments, and outcomes during 6 months of follow-up.

RESULTS

Of 1051 patients screened, 793 were diagnosed with a CNS infection. Patients (median age 33 years, 62% male, 38% HIV-infected) presented a median of 14 days (IQR 7-30) after symptom onset, often with altered consciousness (63%), motor deficits (73%), and seizures (21%). Among HIV-uninfected patients, CNS tuberculosis (TB) was most common (60%), while viral (8%) and bacterial (4%) disease were uncommon. Among HIV-infected patients, cerebral toxoplasmosis (41%) was most common, followed by CNS TB (19%), neurosyphilis (15%), and cryptococcal meningitis (10%). A microbiologically confirmed diagnosis was achieved in 25% of cases, and initial diagnoses were revised in 46% of cases. In-hospital mortality was 30%, and at six months, 45% of patients had died, and 12% suffered from severe disability. Six-month mortality was associated with older age, HIV, and severe clinical, radiological and CSF markers at presentation.

CONCLUSION

CNS infections in Indonesia are characterized by late presentation, severe disease, frequent HIV coinfection, low microbiological confirmation and high mortality. These findings highlight the need for earlier disease recognition, faster and more accurate diagnosis, and optimized treatment, coupled with wider efforts to improve the uptake of HIV services.

A Specific Pattern of Routine Cerebrospinal Fluid Parameters Might Help to Identify Cases of West Nile Virus Neuroinvasive Disease

BACKGROUND

Viral meningitis/encephalitis (ME) is a rare but potentially harmful disease. The prompt identification of the respective virus is important to guide not only treatment but also potential public health countermeasures. However, in about 40% of cases, no virus is identified despite an extensive diagnostic workup. The aim of the present study was to analyze demographic, seasonal, and routine cerebrospinal fluid (CSF) parameters in cases of viral ME and assess their utility for the prediction of the causative virus.

METHODS

Demographic data, season, and routine CSF parameters (total leucocytes, CSF cell differentiation, age-adjusted CSF/serum albumin ratio, and total immunoglobulin ratios) were retrospectively assessed in cases of viral ME.

RESULTS

In total, 156 cases of acute viral ME (74 female, median age 40.0 years) were treated at a tertiary-care hospital in Germany. Specific viral infections were detected in 93 (59.6%) cases. Of these, 14 (9.0%) cases were caused by herpes simplex virus (HSV), 36 (23.1%) by varicella-zoster virus (VZV), 27 (17.3%) by enteroviruses, 9 (5.8%) by West Nile virus (WNV), and 7 (4.5%) by other specific viruses. Additionally, 64 (41.0%) cases of ME of unknown viral etiology were diagnosed. Cases of WNV ME were older, predominantly male, showed a severe disruption of the blood-CSF-barrier, a high proportion of neutrophils in CSF, and an intrathecal total immunoglobulin M synthesis in the first CSF sample. In a multinominal logistic regression analysis, the accuracy of these CSF parameters together with age and seasonality was best for the prediction of WNV (87.5%), followed by unknown viral etiology (66.7%), VZV (61.8%), and enteroviruses (51.9%).

CONCLUSIONS

Cases with WNV ME showed a specific pattern of routine CSF parameters and demographic data that allowed for their identification with good accuracy. These findings might help to guide the diagnostic workup in cases with viral ME, in particular allowing the timely identification of cases with ME due to WNV.

Characteristics and long-term prognosis of Danish residents with a positive intrathecal antibody index test for herpes simplex virus or varicella-zoster virus compared with individuals with a positive cerebrospinal fluid PCR: a nationwide cohort study

OBJECTIVES

We compared characteristics and outcomes of individuals who in the cerebrospinal fluid (CSF) were positive for herpes simplex virus (HSV) or varicella-zoster virus (VZV)-intrathecal antibody index test ([AI]-positive) vs. individuals who were PCR-positive for HSV type 1 (HSV1), type 2 (HSV2), and for VZV.

METHODS

Nationwide cohort study of all Danish residents with positive CSF-AI or -PCR for HSV or VZV (1995-2021). We calculated short- and long-term risks as age-, sex-, and comorbidity-adjusted odds ratios (aOR), adjusted hazard ratios (aHR), and absolute risk differences with 95% CIs.

RESULTS

Compared with individuals with positive PCR for HSV1 (n = 321), HSV2 (n = 497), and VZV (n = 1054), individuals with a positive AI for HSV (n = 177) and VZV (n = 219) had CSF pleocytosis less frequently (leucocyte count >10/μL: HSV-AI: 39%, VZV-AI: 52%, HSV1-PCR: 81%, HSV2-PCR: 92%, VZV-PCR: 83%), and were less frequently diagnosed with central nervous system infection ([aOR {95%CI}]: HSV-AI vs. HSV1-PCR: [0.1 {0.1, 0.2}], HSV-AI vs. HSV2-PCR: [0.1 {0.0, 0.1}], VZV-AI vs. VZV-PCR: [0.2 {0.2, 0.3}]). Individuals with a positive HSV-AI or VZV-AI had increased risk of demyelinating disease ([aOR {95%CI}; aHR {95%CI}]: HSV-AI vs. HSV1-PCR: [4.6 {0.9, 24.5}; aHR not applicable], HSV-AI vs. HSV2-PCR: [10.4 {2.3, 45.9}; 12.4 {2.3, 66.0}], VZV-AI vs. VZV-PCR: [aOR not applicable; 10.3 {1.8, 58.8}]). Disability pension was less frequent among HSV-AI than HSV1-PCR cohort members (5-year risk difference: -23.6%, 95%CI: -35.2, -11.8), and more frequent among VZV-AI than VZV-PCR cohort members (5-year risk difference: 16.8%, 95%CI: 5.0, 28.7).

DISCUSSION

AI-positive individuals differ from PCR-positive individuals in several aspects. AI appears unspecific for current central nervous system infections.

Clinical features, etiologies, and outcomes of central nervous system infections in intensive care: A multicentric retrospective study in a large Brazilian metropolitan area

PURPOSE

The goal of this study was to investigate severe central nervous system infections (CNSI) in adults admitted to the intensive care unit (ICU). We analyzed the clinical presentation, causes, and outcomes of these infections, while also identifying factors linked to higher in-hospital mortality rates.

MATERIALS AND METHODS

We conducted a retrospective multicenter study in Rio de Janeiro, Brazil, from 2012 to 2019. Using a prediction tool, we selected ICU patients suspected of having CNSI and reviewed their medical records. Multivariate analyses identified variables associated with in-hospital mortality.

RESULTS

In a cohort of 451 CNSI patients, 69 (15.3%) died after a median 11-day hospitalization (5-25 IQR). The distribution of cases was as follows: 29 (6.4%) had brain abscess, 161 (35.7%) had encephalitis, and 261 (57.8%) had meningitis. Characteristics: median age 41 years (27-53 IQR), 260 (58%) male, and 77 (17%) HIV positive. The independent mortality predictors for encephalitis were AIDS (OR = 4.3, p = 0.01), ECOG functional capacity limitation (OR = 4.0, p < 0.01), ICU admission from ward (OR = 4.0, p < 0.01), mechanical ventilation ≥10 days (OR = 6.1, p = 0.04), SAPS 3 ≥ 55 points (OR = 3.2, p = 0.02). Meningitis: Age > 60 years (OR = 234.2, p = 0.04), delay >3 days for treatment (OR = 2.9, p = 0.04), mechanical ventilation ≥10 days (OR = 254.3, p = 0.04), SOFA >3 points (OR = 2.7, p = 0.03). Brain abscess: No associated factors found in multivariate regression.

CONCLUSIONS

Patients' overall health, prompt treatment, infection severity, and prolonged respiratory support in the ICU all significantly affect in-hospital mortality rates. Additionally, the implementation of CNSI surveillance with the used prediction tool could enhance public health policies.

Infectious Myelopathies

OBJECTIVE

Infectious myelopathy of any stage and etiology carries the potential for significant morbidity and mortality. This article details the clinical presentation, risk factors, and key diagnostic components of infectious myelopathies with the goal of improving the recognition of these disorders and guiding subsequent management.

LATEST DEVELOPMENTS

Despite our era of advanced multimodal imaging and laboratory diagnostic technology, a causative organism often remains unidentified in suspected infectious and parainfectious myelopathy cases. To improve diagnostic capability, newer technologies such as metagenomics are being harnessed to develop diagnostic assays with a greater breadth of data from each specimen and improvements in infection identification. Conventional assays have been optimized for improved sensitivity and specificity.

ESSENTIAL POINTS

Prompt recognition and treatment of infectious myelopathy decreases morbidity and mortality. The key diagnostic tools include serologies, CSF analysis, and imaging; however clinical presentation, epidemiologic risk factors, and history of recent illness are all vital to making the proper diagnosis because current laboratory and imaging modalities are often inconclusive. The cornerstone of recommended treatment is targeted antimicrobials with appropriate immune modulation, surgical intervention, supportive care, and interdisciplinary involvement, all of which further improve outcomes for patients with infectious myelopathy.

A retrospective analysis of 20,178 adult neurological infection admissions to United Kingdom critical care units from 2001 to 2020

BACKGROUND

Neurological infection is an important cause of critical illness, yet little is known on the epidemiology of neurological infections requiring critical care.

METHODS

We analysed data on all adults with proven or probable neurological infection admitted to UK (NHS) critical care units between 2001 and 2020 reported to the Intensive Care National Audit and Research Centre. Diagnoses, physiological variables, organ support and clinical outcomes were analysed over the whole period, and for consecutive 5-year intervals within it. Predictors of in-hospital mortality were identified using a backward stepwise regression model.

RESULTS

We identified 20,178 critical care admissions for neurological infection. Encephalitis was the most frequent presentation to critical care, comprising 6725 (33.3%) of 20,178 cases. Meningitis- bacterial, viral or unspecified cases - accounted for 10,056 (49.8%) of cases. In-hospital mortality was high, at 3945/19,765 (20.0%) overall. Over the four consecutive 5-year periods, there were trends towards higher Glasgow Coma Scale scores on admission, longer critical care admissions (from median 4 [IQR 2-8] to 5 days [IQR 2-10]), and reduced in-hospital mortality (from 24.9 to 18.1%). We identified 12 independent predictors of in-hospital death which when used together showed good discrimination between patients who die and those who survive (AUC = 0.79).

CONCLUSIONS

Admissions with neurological infection to UK critical care services are increasing and the mortality, although improving, remains high. To further improve outcomes from severe neurological infection, novel approaches to the evaluation of risk stratification, monitoring and management strategies are required.

Understanding the Neurotrophic Virus Mechanisms and Their Potential Effect on Systemic Lupus Erythematosus Development

Central nervous system (CNS) pathologies are a public health concern, with viral infections one of their principal causes. These viruses are known as neurotropic pathogens, characterized by their ability to infiltrate the CNS and thus interact with various cell populations, inducing several diseases. The immune response elicited by neurotropic viruses in the CNS is commanded mainly by microglia, which, together with other local cells, can secrete inflammatory cytokines to fight the infection. The most relevant neurotropic viruses are adenovirus (AdV), cytomegalovirus (CMV), enterovirus (EV), Epstein-Barr Virus (EBV), herpes simplex virus type 1 (HSV-1), and herpes simplex virus type 2 (HSV-2), lymphocytic choriomeningitis virus (LCMV), and the newly discovered SARS-CoV-2. Several studies have associated a viral infection with systemic lupus erythematosus (SLE) and neuropsychiatric lupus (NPSLE) manifestations. This article will review the knowledge about viral infections, CNS pathologies, and the immune response against them. Also, it allows us to understand the relevance of the different viral proteins in developing neuronal pathologies, SLE and NPSLE.

Adult risk groups for vaccine preventable respiratory infections: an overview of the UK environment

INTRODUCTION

Vaccine-preventable respiratory infections (VPRI) including those caused by Streptococcus pneumoniae, influenza, respiratory syncytial virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pose substantial challenges to health and social care systems. In the UK, routine adult respiratory vaccination programs are in place. The objective of this article is to review the current evidence on the impact of four seasonal VPRIs in adults risk group definitions and to explore the strengths and limitations of current recommendations, and to identify evidence gaps for further research.

AREAS COVERED

Relevant evidence on UK data from surveillance systems, observational studies and publicly available government documents is collated and reviewed, as well as selected global data.

EXPERT OPINION

Disparities exist between adult risk group categories for different respiratory vaccination programs as defined in the current vaccination guidance. The burden of multiple respiratory pathogens signifies importance of routine multi-pathogen testing with the need for a resilient and large-scale national surveillance system. Further understanding of epidemiological trends and disease burden will help guide decision-making and planning of targeted strategies for disease prevention and control. Addressing inequalities in disease burden and vaccine coverage particularly in clinical risk groups, and promoting equitable vaccine access remain a priority.

Serologic and Genomic Investigation of West Nile Virus in Kosovo

The prevalence of West Nile virus (WNV) is increasing across Europe, with cases emerging in previously unaffected countries. Kosovo is situated in a WNV-endemic region where the seroepidemiological data on WNV in humans remains absent. To address this issue, we have conducted a seroepidemiological investigation of 453 randomly selected sera from a hospital in Kosovo, revealing a 1.55% anti-WNV IgG seroprevalence. Comparative and phylogeographic analyses of the WNV genomes obtained by sequencing archived samples from patients with West Nile fever indicate at least two recent and distinct introductions of WNV lineage 2 into Kosovo from neighboring countries. These findings confirm the eco-epidemiological status of WNV in southeast Europe, where long- and short-range dispersion of lineage 2 strains contributes to a wider circulation via central Europe. Our results suggest an increasing risk for WNV spreading in Kosovo, underscoring the need for an integrated national surveillance program targeting vectors and avian populations for early epidemic detection, as well as the screening of blood donors to gauge the impact of virus circulation on the human population.

Pre-hospital symptoms associated with acute bacterial meningitis differs between children and adults

Community acquired bacterial meningitis (CABM) is a medical emergency requiring timely appropriate action. More knowledge about pre-hospital symptoms is needed. Retrospective observational study of pre-hospital management in patients with CABM between 2016 and 2021 admitted to a hospital in the Capital Region of Denmark. Reported symptoms were extracted from archived audio files of the initial phone call to emergency medical service. The majority of the 209 patients (82%) were adults. The most common symptoms were altered mental state (58%) and fever (57%), while neck stiffness was less common (9%). Children more often presented with fever, fatigue, rashes, and neck stiffness, while adults more often presented with altered mental state, and leg pain. Most patients (85%) reported at least 1 of the 3 symptoms in the classical triad of meningitis, while 3% reported all 3. Children more often presented at least 2 of 3 symptoms in the triad. One child (3%) and 7 adults (4%) received antibiotics pre-admission. Patients with CABM reported a variety of symptoms that differed significantly in children and adults. The classic triad was rare. Very few patients received antibiotics pre-admission. We suggest that questioning relevant symptoms should be done in febrile or mentally altered patients.

Cognitive dysfunction in post-COVID-19 condition: Mechanisms, management, and rehabilitation

The long-term effects of COVID-19 on cognitive function have become an area of increasing concern. This paper provides an overview of characteristics, risk factors, possible mechanisms, and management strategies for cognitive dysfunction in post-COVID-19 condition (PCC). Prolonged cognitive dysfunction is one of the most common impairments in PCC, affecting between 17% and 28% of the individuals more than 12 weeks after the infection and persisting in some cases for several years. Cognitive dysfunctions can be manifested as a wide range of symptoms including memory impairment, attention deficit, executive dysfunction, and reduced processing speed. Risk factors for developing PCC, with or without cognitive impairments, include advanced age, preexisting medical conditions, and the severity of acute illness. The underlying mechanisms remain unclear, but proposed contributors include neuroinflammation, hypoxia, vascular damage, and latent virus reactivation not excluding the possibility of direct viral invasion of the central nervous system, illustrating complex viral pathology. As the individual variation of the cognitive impairments is large, a neuropsychological examination and a person-centered multidimensional approach are required. According to the World Health Organization, limited evidence on COVID-19-related cognitive impairments necessitates implementing rehabilitation interventions from established practices of similar conditions. Psychoeducation and compensatory skills training are recommended. Assistive products and environmental modifications adapted to individual needs might be helpful. In specific attention- and working memory dysfunctions, cognitive training-carefully monitored for intensity-might be effective for people who do not suffer from post-exertional malaise. Further research is crucial for evidence-based interventions specific to COVID-19-related cognitive impairments.

Untargeted metagenomic sequencing identifies Toscana virus in patients with idiopathic meningitis, southern Spain, 2015 to 2019

BackgroundVarious pathogens, including bacteria, fungi, parasites, and viruses can lead to meningitis. Among viruses causing meningitis, Toscana virus (TOSV), a phlebovirus, is transmitted through sandfly bites. TOSV infection may be suspected if patients with enterovirus- and herpesvirus-negative aseptic (non-bacterial) meningitis recall recent insect bites. Other epidemiological factors (season, rural area) may be considered. The broad range of possible meningitis aetiologies poses considerable diagnosis challenges. Untargeted metagenomic next-generation sequencing (mNGS) can potentially identify pathogens, which are not considered or detected in routine diagnostic panels.AimIn this retrospective, single-centre observational study, we investigated mNGS usefulness to understand the cause of meningitis when conventional approaches fail.MethodsCerebrospinal fluid (CSF) samples from patients hospitalised in southern Spain in 2015-2019 with aseptic meningitis and no aetiology found by conventional testing, were subjected to mNGS. Patients' demographic characteristics had been recorded and physicians had asked them about recent insect bites. Obtained viral genome sequences were phylogenetically analysed.ResultsAmong 23 idiopathic cases, TOSV was identified in eight (all male; median age:  39 years, range: 15-78 years). Five cases lived in an urban setting, three occurred in autumn and only one recalled insect bites. Phylogenetic analysis of TOSV segment sequences supported one intra-genotype reassortment event.ConclusionsOur study highlights the usefulness of mNGS for identifying viral pathogens directly in CSF. In southern Spain, TOSV should be considered regardless of recalling of insect bites or other epidemiological criteria. Detection of a disease-associated reassortant TOSV emphasises the importance of monitoring the spread and evolution of phleboviruses in Mediterranean countries.

Clinical features and prognostic factors in adults with viral meningitis

Clinical features applicable to the entire spectrum of viral meningitis are limited, and prognostic factors for adverse outcomes are undetermined. This nationwide population-based prospective cohort study included all adults with presumed and microbiologically confirmed viral meningitis in Denmark from 2015 until 2020. Prognostic factors for an unfavourable outcome (Glasgow Outcome Scale score of 1-4) 30 days after discharge were examined by modified Poisson regression. In total, 1066 episodes of viral meningitis were included, yielding a mean annual incidence of 4.7 episodes per 100 000 persons. Pathogens were enteroviruses in 419/1066 (39%), herpes simplex virus type 2 in 171/1066 (16%), varicella-zoster virus in 162/1066 (15%), miscellaneous viruses in 31/1066 (3%) and remained unidentified in 283/1066 (27%). The median age was 33 years (IQR 27-44), and 576/1066 (54%) were females. In herpes simplex virus type 2 meningitis, 131/171 (77%) were females. Immunosuppression [32/162 (20%)] and shingles [90/149 (60%)] were frequent in varicella-zoster virus meningitis. The triad of headache, neck stiffness and hyperacusis or photophobia was present in 264/960 (28%). The median time until lumbar puncture was 3.0 h (IQR 1.3-7.1), and the median CSF leucocyte count was 160 cells/µl (IQR 60-358). The outcome was unfavourable in 216/1055 (20%) 30 days after discharge. Using unidentified pathogen as the reference, the adjusted relative risk of an unfavourable outcome was 1.34 (95% CI 0.95-1.88) for enteroviruses, 1.55 (95% CI 1.00-2.41) for herpes simplex virus type 2, 1.51 (95% CI 0.98-2.33) for varicella-zoster virus and 1.37 (95% CI 0.61-3.05) for miscellaneous viruses. The adjusted relative risk of an unfavourable outcome was 1.34 (95% CI 1.03-1.75) for females. Timing of acyclovir or valacyclovir was not associated with the outcome in meningitis caused by herpes simplex virus type 2 or varicella-zoster virus. In summary, the outcome of viral meningitis was similar among patients with different aetiologies, including those with presumed viral meningitis but without an identified pathogen. Females had an increased risk of an unfavourable outcome. Early antiviral treatment was not associated with an improved outcome in meningitis caused by herpes simplex virus type 2 or varicella-zoster virus.

RNA-sequencing-based detection of human viral pathogens in cerebrospinal fluid and serum samples from children with meningitis and encephalitis

Encephalitis and meningitis are notable global public health concerns, especially among infants or children. Metagenomic next-generation sequencing (mNGS) has greatly advanced our understanding of the viruses responsible for these diseases. However, the detection rate of the aetiology remains low. We conducted RNA sequencing and virome analysis on cerebrospinal fluid (CSF) and serum samples commonly used in the clinical diagnosis to detect viral pathogens. In total, 226 paired CSF and serum samples from 113 children with encephalitis and meningitis were enrolled. The results showed that the diversity of viruses was higher in CSF, with a total of 12 viral taxa detected, including one case each of herpesvirus, coronavirus and enterovirus, and six cases of adenovirus related to human diseases. In contrast, the Anelloviridae was the most abundant viral family detected in serum, and only a few samples contained human viral pathogens, including one case of enterovirus and two cases of adenovirus. The detection rate for human viral pathogens increases to 10.6 %(12/113) when both types of samples are used simultaneously, compared to CSF along 7.9 % (9/113) or serum alone 2.6 % (3/113). However, we did not detect these viruses simultaneously in paired samples from the same case. These results suggest that CSF samples still have irreplaceable advantages for using mNGS to detect viruses in patients with meningitis and encephalitis, and serum can supplement to improve the detection rate of viral encephalitis and meningitis. The findings of this study could help improve the etiological diagnosis, clinical management and prognosis of patients with meningitis and encephalitis in children.

Viral meningitis and encephalitis: an update

PURPOSE OF REVIEW

The most common infectious etiologies of meningitis and encephalitis are viruses. In this review, we will discuss current epidemiology, prevention, diagnosis, and treatment of the most common causes of viral meningitis and encephalitis worldwide.

RECENT FINDINGS

Viral meningitis and encephalitis are increasingly diagnosed as molecular diagnostic techniques and serologies have become more readily available worldwide but recent progress in novel antiviral therapies remains limited. Emerging and re-emerging viruses that have caused endemic or worldwide outbreaks or epidemics are arboviruses (e.g., West Nile virus, Japanese encephalitis, Tick borne encephalitis, Dengue, Zika, Toscana), enteroviruses (e.g., Enterovirus 71, Enterovirus D68), Parechoviruses, respiratory viruses [e.g., severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza, metapneumoviruses, measles, mumps], and herpes viruses [e.g., herpes simplex virus (HSV) type 1 (HSV-1), HSV-2, human herpes (HV) 6, varicella zoster virus (VZV)]. Future efforts should concentrate in increasing availability for those viruses with effective vaccination [e.g., Japanese encephalitis, Tick borne encephalitis, varicella zoster viruses, SARS-CoV-2, influenza], prompt initiation of those with encephalitis with treatable viruses (e.g., HSV-1, VZV), increasing the diagnostic yield by using novel techniques such as metagenomic sequencing and avoiding unnecessary antibiotics in those with viral meningitis or encephalitis.

SUMMARY

We review the current epidemiology, clinical presentation, diagnosis, and treatment of the common causative agents of viral meningitis and encephalitis worldwide.

Clinical features, etiologies, and outcomes in adult patients with meningoencephalitis requiring intensive care (EURECA): an international prospective multicenter cohort study

PURPOSE

We aimed to characterize the outcomes of patients with severe meningoencephalitis requiring intensive care.

METHODS

We conducted a prospective multicenter international cohort study (2017-2020) in 68 centers across 7 countries. Eligible patients were adults admitted to the intensive care unit (ICU) with meningoencephalitis, defined by an acute onset of encephalopathy (Glasgow coma scale (GCS) score [Formula: see text] 13), a cerebrospinal fluid pleocytosis [Formula: see text] 5 cells/mm3, and at least two of the following criteria: fever, seizures, focal neurological deficit, abnormal neuroimaging, and/or electroencephalogram. The primary endpoint was poor functional outcome at 3 months, defined by a score of three to six on the modified Rankin scale. Multivariable analyses stratified on centers investigated ICU admission variables associated with the primary endpoint.

RESULTS

Among 599 patients enrolled, 589 (98.3%) completed the 3-month follow-up and were included. Overall, 591 etiologies were identified in those patients which were categorized into five groups: acute bacterial meningitis (n = 247, 41.9%); infectious encephalitis of viral, subacute bacterial, or fungal/parasitic origin (n = 140, 23.7%); autoimmune encephalitis (n = 38, 6.4%); neoplastic/toxic encephalitis (n = 11, 1.9%); and encephalitis of unknown origin (n = 155, 26.2%). Overall, 298 patients (50.5%, 95% CI 46.6-54.6%) had a poor functional outcome, including 152 deaths (25.8%). Variables independently associated with a poor functional outcome were age > 60 years (OR 1.75, 95% CI 1.22-2.51), immunodepression (OR 1.98, 95% CI 1.27-3.08), time between hospital and ICU admission > 1 day (OR 2.02, 95% CI 1.44-2.99), a motor component on the GCS [Formula: see text] 3 (OR 2.23, 95% CI 1.49-3.45), hemiparesis/hemiplegia (OR 2.48, 95% CI 1.47-4.18), respiratory failure (OR 1.76, 95% CI 1.05-2.94), and cardiovascular failure (OR 1.72, 95% CI 1.07-2.75). In contrast, administration of a third-generation cephalosporin (OR 0.54, 95% CI 0.37-0.78) and acyclovir (OR 0.55, 95% CI 0.38-0.80) on ICU admission were protective.

CONCLUSION

Meningoencephalitis is a severe neurologic syndrome associated with high mortality and disability rates at 3 months. Actionable factors for which improvement could be made include time from hospital to ICU admission, early antimicrobial therapy, and detection of respiratory and cardiovascular complications at admission.

An Adagio for Viruses, Played Out on Ancient DNA

Studies of ancient DNA have transformed our understanding of human evolution. Paleogenomics can also reveal historic and prehistoric agents of disease, including endemic, epidemic, and pandemic pathogens. Viruses-and in particular those with single- or double-stranded DNA genomes-are an important part of the paleogenomic revolution, preserving within some remains or environmental samples for tens of thousands of years. The results of these studies capture the public imagination, as well as giving scientists a unique perspective on some of the more slowly evolving viruses which cause disease. In this review, we revisit the first studies of historical virus genetic material in the 1990s, through to the genomic revolution of recent years. We look at how paleogenomics works for viral pathogens, such as the need for careful precautions against modern contamination and robust computational pipelines to identify and analyze authenticated viral sequences. We discuss the insights into virus evolution which have been gained through paleogenomics, concentrating on three DNA viruses in particular: parvovirus B19, herpes simplex virus 1, and smallpox. As we consider recent worldwide transmission of monkeypox and synthetic biology tools that allow the potential reconstruction of extinct viruses, we show that studying historical and ancient virus evolution has never been more topical.

Pentraxin 3 in the cerebrospinal fluid during central nervous system infections: A retrospective cohort study

The present study describes diagnostic and prognostic abilities of Cerebrospinal fluid (CSF) Pentraxin 3 (PTX3) in central nervous system (CNS) infections. CSF PTX3 was measured retrospectively from 174 patients admitted under suspicion of CNS infection. Medians, ROC curves and Youdens index was calculated. CSF PTX3 was significantly higher among all CNS infections and undetectable in most of the patients in the control group, and significantly higher in bacterial infections compared to viral and Lyme infections. No association was found between CSF PTX3 and Glasgow Outcome Score. PTX3 in the CSF can distinguish bacterial infection from viral and Lyme infections and non-CNS infections. Highest levels were found in bacterial meningitis. No prognostic abilities were found.

A risk score for identifying patients at a low risk of bacterial meningitis amongst adults with cerebrospinal fluid leucocytosis and a negative gram stain result: a derivation and validation study

OBJECTIVES

We aimed to derive and validate a risk score to differentiate patients with bacterial meningitis from those with viral meningitis or encephalitis amongst patients presenting with cerebrospinal fluid (CSF) leucocytosis and a negative Gram staining result.

METHODS

We included adults with bacterial and viral meningitis or encephalitis presenting with CSF leukocyte counts of >10 per mm³ and a negative Gram staining result from cohorts in Houston, Texas (2004-2019), and the Netherlands (2012-2021). Derivation and the first validation were performed in the American patients and further validation in the Dutch patients.

RESULTS

Derivation was performed in 109 American patients with bacterial meningitis (median age, 56 years; interquartile range [IQR], 46-66 years; 46% women) and 194 with viral meningitis or encephalitis (median age, 46 years; IQR, 33-60 years; 53% women). Serum leukocyte counts of >10.0 × 10⁹/L, CSF leukocyte counts of >2000 per mm³, granulocyte counts of >1180 per mm³, protein levels of >2.2 g/L, glucose levels of <1.9 mmol/L and fever on admission were included in the risk score, which was dichotomized into 'low risk' (0 present) and 'high risk' (>0 present). The first validation showed a sensitivity of 100% (95% CI, 96.6-100) and specificity of 34.0% (95% CI, 27.4-41.2). Further validation in 262 Dutch patients with bacterial meningitis (median age, 57 years; IQR 44-70 years; 45% women) and 68 with viral meningitis (median age, 34 years; IQR, 28-45 years; 60% women) showed a sensitivity of 99.6% (95% CI, 97.9-100) and specificity of 41.2% (95% CI, 29.4-53.7).

CONCLUSIONS

Our risk score may be able to rule out bacterial meningitis amongst patients presenting with CSF leucocytosis and a negative Gram staining result. However, it needs prospective testing prior to clinical implementation.

Case report: Clinical and virological characteristics of aseptic meningitis caused by a recombinant echovirus 18 in an immunocompetent adult

Echovirus 18 has been recognized as an important causative pathogen of aseptic meningitis in young children worldwide, and echovirus 18-induced meningitis is rarely found in adults with immunocompetence. In this case study, we report the clinical and virological characteristics of aseptic meningitis caused by recombinant echovirus 18 in an adult with immunocompetence. A 31-year-old woman with immunocompetence was admitted to our hospital with fever, dizziness, severe headache, nausea, and vomiting for the past 1 day and was diagnosed with viral meningitis based on the clinical manifestations and laboratory results from cerebrospinal fluid (CSF). The patient received antiviral treatment with ribavirin and interferon as soon as the enterovirus infection was identified using qRT-PCR and was cured after 4 days. From the oropharyngeal swab and CSF samples, two echovirus 18 strains were isolated with a single nucleotide difference located at the 5' UTR. Phylogenetic analyses based on the VP1 gene showed that the two strains belonged to the subgenotype C2 and were clustered with sequences obtained from China after 2015, while the results from the 3D polymerase region showed that the two strains were closely related to the E30 strains. Bootscanning results using the 5' UTR to 2A region and the 2B to 3' UTR region showed that potential intertypic recombination had occurred in the 2B gene. Recombination analyses further confirmed that the two strains (echovirus 18) presented genome recombination with echovirus 30 in the nucleotide regions of the 2B gene. To the best of our knowledge, this is the first report of echovirus 18-induced meningitis in an adult with immunocompetence from mainland China, highlighting the need for close surveillance of echovirus 18 both in children and adults in the future.

Epidemiological characteristics and climatic variability of viral meningitis in Kazakhstan, 2014-2019

Background

The comprehensive epidemiology and impact of climate on viral meningitis (VM) in Kazakhstan are unknown. We aimed to study the incidence, in-hospital mortality and influence of climatic indicators on VM from 2014 to 2019.

Methods

Nationwide electronic healthcare records were used to explore this study. ICD-10 codes of VM, demographics, and hospital outcomes were evaluated using descriptive statistics and survival analysis.

Results

During the 2014-2019 period, 10,251 patients with VM were admitted to the hospital. 51.35% of them were children, 57.85% were males, and 85.9% were from the urban population. Enteroviral meningitis was the main cause of VM in children. The incidence rate was 13 and 18 cases per 100,000 population in 2014 and 2019, respectively. Case fatality rate was higher in 2015 (2.3%) and 2017 (2.0%). The regression model showed 1°C increment in the daily average temperature might be associated with a 1.05-fold (95% CI 1.047-1.051) increase in the daily rate of VM cases, 1hPa increment in the average air pressure and 1% increment in the daily average humidity might contribute to a decrease in the daily rate of VM cases with IRRs of 0.997 (95% CI 0.995-0.998) and 0.982 (95% CI 0.981-0.983), respectively. In-hospital mortality was 35% higher in males compared to females. Patients residing in rural locations had a 2-fold higher risk of in-hospital death, compared to city residents. Elderly patients had a 14-fold higher risk of in-hospital mortality, compared to younger patients.

Conclusion

This is the first study in Kazakhstan investigating the epidemiology and impact of climate on VM using nationwide healthcare data. There was a tendency to decrease the incidence with outbreaks every 5 years, and mortality rates were higher for Russians and other ethnicities compared to Kazakhs, for males compared to females, for elder patients compared to younger patients, and for patients living in rural areas compared to city residents. The climatic parameters and the days of delay indicated a moderate interaction with the VM cases.

Surveillance of tick-borne encephalitis in emerging risk areas in southern Sweden: a retrospective case finding study

Tick-borne encephalitis (TBE) is an emerging infection causing CNS infection of various severity. Good knowledge of the incidence in the population and defined risk areas is important in risk communication and vaccination recommendations. The aim of this study was to investigate potential underreporting by retrospectively diagnose TBE among patients with viral CNS infections of unknown etiology in a region with emerging risk areas for TBE, and define variables associated with performed TBE serology at the time of infection. Epidemiological data and microbiological diagnostics of cases with viral CNS infection of unknown etiology treated at departments of infectious diseases and pediatrics in Skåne County during 2000-2012 were investigated. Analyses to evaluate variables associated with performed TBE serology at the time of infection were performed. Retrospective TBE serology was performed on stored blood samples when available. TBE serology was already performed at the time of CNS infection in 193 out of 761 cases. Department, type of clinical manifestation, time period of illness, and whether Borrelia serology had been performed were independent variables associated with having had TBE serology performed or not at the time of illness. Only one of 137 cases, where samples could be retrospectively analyzed for TBE, turned out positive. This study shows a low frequency of TBE sampling among patients with meningoencephalitis in a region with emerging risk for TBE. A higher awareness of TBE as differential diagnosis could contribute to earlier detection of new risk areas and adequate preventive advice to the public.

Bacterial ribosomal RNA detection in cerebrospinal fluid using a viromics approach

BACKGROUND

In patients with central nervous system (CNS) infections identification of the causative pathogen is important for treatment. Metagenomic next-generation sequencing techniques are increasingly being applied to identify causes of CNS infections, as they can detect any pathogen nucleic acid sequences present. Viromic techniques that enrich samples for virus particles prior to sequencing may simultaneously enrich ribosomes from bacterial pathogens, which are similar in size to small viruses.

METHODS

We studied the performance of a viromic library preparation technique (VIDISCA) combined with low-depth IonTorrent sequencing (median ~ 25,000 reads per sample) for detection of ribosomal RNA from common pathogens, analyzing 89 cerebrospinal fluid samples from patients with culture proven bacterial meningitis.

RESULTS

Sensitivity and specificity to Streptococcus pneumoniae (n = 24) before and after optimizing threshold parameters were 79% and 52%, then 88% and 90%. Corresponding values for Neisseria meningitidis (n = 22) were 73% and 93%, then 67% and 100%, Listeria monocytogenes (n = 24) 21% and 100%, then 27% and 100%, and Haemophilus influenzae (n = 18) 56% and 100%, then 71% and 100%. A higher total sequencing depth, no antibiotic treatment prior to lumbar puncture, increased disease severity, and higher c-reactive protein levels were associated with pathogen detection.

CONCLUSION

We provide proof of principle that a viromic approach can be used to correctly identify bacterial ribosomal RNA in patients with bacterial meningitis. Further work should focus on increasing assay sensitivity, especially for problematic species (e.g. L. monocytogenes), as well as profiling additional pathogens. The technique is most suited to research settings and examination of idiopathic cases, rather than an acute clinical setting.

Treatment of Herpes Simplex Virus Type 2 Meningitis: A Survey Among Infectious Diseases Specialists in France, Sweden, Australia, and Denmark

Background

We aimed to describe attitudes toward treatment of herpes simplex virus type 2 (HSV-2) meningitis and prioritize future trials.

Methods

This was a self-administered online survey of HSV-2 meningitis treatment among infectious diseases (ID) specialists in France, Sweden, Australia, and Denmark.

Results

A total of 223 ID specialists (45% female) from France (36%), Denmark (24%), Sweden (21%), and Australia (19%) participated in the survey, primarily from university hospitals (64%). The estimated overall response rate was 11% and ranged from 6% (Australia) to 64% (Denmark). Intravenous (IV) acyclovir followed by oral valacyclovir was the favored treatment in 110 of 179 (61%), whereas monotherapy with either IV acyclovir or oral valacyclovir was used by 35 of 179 (20%) and 34 of 179 (19%), respectively. The median total duration was reported to be 7 days (interquartile range, 7-10 days) regardless of antiviral regimen. Immunocompromise influenced decisions on antiviral treatment in 110 of 189 (58%) of respondents, mainly by prolonged total duration of treatment (36/110 [33%]), prolonged IV administration (31/110 [28%]), and mandatory antiviral treatment (25/110 [23%]). Treatment with acyclovir/valacyclovir versus placebo and comparison of acyclovir versus valacyclovir were assigned the highest prioritization scores for future randomized controlled trials on HSV-2 meningitis.

Conclusions

Perceptions of indications for as well as type and duration of antiviral treatment varied substantially among ID specialists.

Primary HSV-2 Infection Complicated by Radiculomyelitis in a Young Immunocompetent Female Patient with Inherited Chromosomally Integrated HHV-6: A Case Report

Background: HSV-1, HSV-2 and VZV are alpha Herpesviruses, neurotropic viruses that are associated with various neurologic complications upon primary infection or reactivation. Cases of myelitis and radiculomyelitis are rare and appropriate etiologic diagnoses can be tricky. Case presentation: Here we describe the case of a young immunocompetent woman who developed painful and extended vesicular genital lesions, with subsequent radiculomyelitis. HSV-1/-2 PCRs in the cerebrospinal fluid were misleadingly negative, whereas HHV-6 PCR was positive. Positive anti-HSV-2 IgM and IgG in serum was consistent with HSV-2 primary infection. On the other hand, the detection of HHV-6 DNA was explained by inherited chromosomally integrated HHV-6. The clinical course was favorable with high-dose IV acyclovir and corticosteroids. Conclusion: HSV-2-related radiculomyelitis is a rare clinical entity, which can be difficult to diagnose. In this case report, the causative virus was not detected in the patient’s CSF, whereas HHV-6 DNA, non-pathogenic in this situation, was paradoxically positive. The diagnosis was based on the clinical features typical for HSV-2 primary infection, confirmed by the serology results. The delay between the genital lesions and the appearance of the radiculomyelitis, along with the absence of HSV-2 detection in the CSF, suggests a possible immuno-mediated physiopathological process. As for the HHV-6 DNA detection in the patient’s CSF, it was explained by inherited chromosomally integrated HHV-6. This case illustrates how both negative and positive clinical virology results need careful interpretation according to the clinical findings.

The management of acute meningitis: an update

Meningitis remains an important cause of mortality and morbidity. Clinicians should be alert to this diagnosis and have a low threshold for investigation and treatment of meningitis. This article provides an update of current evidence and existing guidelines for the management of suspected acute meningitis in adults in the UK.

Neurofilament light chain in central nervous system infections: a prospective study of diagnostic accuracy

Diagnosing central nervous system (CNS) infections quickly is often difficult. Neurofilament light chain (NfL) is a component of the axonal cytoskeleton and identified as marker of neuronal damage in several CNS diseases. We evaluated the diagnostic accuracy of NfL for diagnosing CNS infections. We included patients from a prospective cohort of consecutive patients in whom a lumbar puncture was performed for suspected CNS infection in an academic hospital in The Netherlands. The index test was NfL in cerebrospinal fluid (CSF) and reference standard the final clinical diagnosis. Diagnostic accuracy was determined using the area-under-the-curve (AUC) with 95% confidence intervals (CI). The association of CSF NfL with clinical characteristics, diagnosis and outcome was evaluated. Between 2012 and 2015, 273 episodes in adults of which sufficient CSF was available were included. CNS infection was diagnosed in 26%(n = 70), CNS inflammatory disease in 7%(n = 20), systemic infection in 32%(n = 87), and other neurological disorders in 33%(n = 90). Median CSF NfL level was 593 pg/ml (IQR 249–1569) and did not discriminate between diagnostic categories or CNS infection subcategories. AUC for diagnosing any CNS infection compared to patients without CNS infections was 0.50 (95% CI 0.42–0.59). Patients presenting with an altered mental status had higher NfL levels compared to other patients. We concluded that NfL cannot discriminate between causes in patients suspected of CNS infections. High concentrations of NfL are associated with severe neurological disease and the prognostic value of NfL in patients with CNS infections should be investigated in future research.