Epidemiology of infectious encephalitis, differences between a prospective study and hospital discharge data

Herpes simplex encephalitis in France: incidence, 6-month rehospitalizations and mortality

BACKGROUND

Herpes simplex encephalitis (HSE) is a disease with unfavorable vital and functional prognoses. There are no recent epidemiological data on HSE at a national level using real-life databases, especially in France. This study aimed to report the incidence, the clinical characteristics and outcomes of the patients with HSE.

METHODS

We conducted a comprehensive retrospective cohort study on all patients hospitalized for HSE in France between 2015 and 2022 using national hospital discharge databases. Incidence, socio-demographic and clinical characteristics (including comorbidities, seizure, stays' features, intensive care supports) were described. The short- (first stay) and long-term (6-month) outcomes were reported, in terms of mortality and rehospitalizations.

RESULTS

1425 HSE patients were included (median age 67 [54-77] years old, M/F sex ratio 1.07), giving a mean yearly hospital incidence of 2.3 [2.1-2.5] per 1,000,000 inhabitants. 51.2% of the patients were admitted in ICU (n = 730), of whom 59.0% were mechanically ventilated. The overall mortality during the first stay was 14.3% (n = 204), up to 17.9% for ICU patients. Within 6 months, among the survivors, 10.1% had at least one rehospitalization related to HSE. At 6 months, 16.5% of all patients had died (n = 235), 20.8% for ICU patients.

CONCLUSION

In France, the incidence of hospitalizations for HSE was 2.3 per 1,000,000 inhabitants with more than half of the patients admitted in ICU and a 6-month in-hospital mortality about 16.5%. This real-life update on the characteristics and severe outcomes of the disease raises awareness among care practitioners, of the serious nature of the disease, and thus can lead to higher vigilance.

Activation of neurotoxic A1-reactive astrocytes by SFTS virus infection accelerates fatal brain damage in IFNAR1-/- mice

Severe fever with thrombocytopenia syndrome (SFTS) has a high mortality rate compared to other infectious diseases. SFTS is particularly associated with a high risk of mortality in immunocompromised individuals, while most patients who die of SFTS exhibit symptoms of severe encephalitis before death. However, the region of brain damage and mechanisms by which the SFTS virus (SFTSV) causes encephalitis remains unknown. Here, we revealed that SFTSV infects the brainstem and spinal cord, which are regions of the brain associated with respiratory function, and motor nerves in IFNAR1-/- mice. Further, we show that A1-reactive astrocytes are activated, causing nerve cell death, in infected mice. Primary astrocytes of SFTSV-infected IFNAR1-/- mice also induced neuronal cell death through the activation of A1-reactive astrocytes. Herein, we showed that SFTSV induces fatal neuroinflammation in the brain regions important for respiratory function and motor nerve, which may underlie mortality in SFTS patients. This study provides new insights for the treatment of SFTS, for which there is currently no therapeutic approach.

The Worldwide Prevalence of Herpes Simplex Virus Encephalitis and Meningitis: A Systematic Review and Meta-Analysis

Given the relatively high frequency of central nervous system infections and considerable mor- tality and morbidity reported to be caused by herpes simplex viruses among the other viral agents, having a clear knowledge about their epidemiological profile seems necessary. This systematic review and meta-analysis aimed to determine the relative frequency and preva- lence of herpes simplex encephalitis and meningitis in patients tested for viral etiologies. A comprehensive systematic review was performed in PubMed, Scopus, and Web of Science databases, searching for studies on the prevalence and relative frequency of herpes sim- plex virus 1 and herpes simplex virus 2 encephalitis and meningitis. Seventy-one studies were included. Overall, the prevalence of herpes simplex virus encephalitis among patients tested was 8% (95% confidence interval, 6%-11%; I2 = 98%) and the prevalence of herpes simplex virus meningitis among aseptic patients tested was 4% (95% confidence interval, 3%-7%; I2 = 95%), and a significant difference was observed by region. The results of our subgroup analysis for herpes simplex virus encephalitis revealed a prevalence of 8% for pediatric patients and ado- lescents and 12% for adults. The results for herpes simplex virus meningitis showed a prevalence of 4% for pediatric patients and adolescents and 9% for adults. We observed significant differ- ences in the frequency of herpes simplex virus 1 and herpes simplex virus 2 detection rates by region. Having high rates of missed cases due to inadequate, highly sensitive paraclinical tests performed on patients with suspected viral central nervous system infection is one of the pos- sible factors. More studies are needed to detect the possible flaws in the process of diagnosis in different regions.

Addressing vaccine-preventable encephalitis in vulnerable populations

PURPOSE OF REVIEW

Vaccinations have been pivotal in lowering the global disease burden of vaccine-preventable encephalitides, including Japanese encephalitis, tick-borne encephalitis, measles encephalitis, and rabies encephalitis, among others.

RECENT FINDINGS

Populations vulnerable to vaccine-preventable infections that may lead to encephalitis include those living in endemic and rural areas, military members, migrants, refugees, international travelers, younger and older persons, pregnant women, the immunocompromised, outdoor, healthcare and laboratory workers, and the homeless. There is scope for improving the availability and distribution of vaccinations, vaccine equity, surveillance of vaccine-preventable encephalitides, and public education and information.

SUMMARY

Addressing these gaps in vaccination strategies will allow for improved vaccination coverage and lead to better health outcomes for those most at risk for vaccine-preventable encephalitis.

Seasonal Trends in the Prevalence and Incidence of Viral Encephalitis in Korea (2015-2019)

Viral infections are a common cause of encephalitis. This study investigated the relationship between the incidence of encephalitis and that of respiratory and enteric viral infections in all age groups from 2015 to 2019, using the Health Insurance Review and Assessment (HIRA) Open Access Big Data Platform. We identified monthly incidence patterns and seasonal trends using the autoregressive integrated moving average (ARIMA). The Granger causality test was used to analyze correlations between encephalitis incidence and the positive detection rate (PDR) at 1-month intervals. A total of 42,775 patients were diagnosed with encephalitis during the study period. The incidence of encephalitis was highest in the winter (26.8%). The PDRs for respiratory syncytial virus (HRSV) and coronavirus (HCoV) were associated with the trend in encephalitis diagnosis in all age groups, with a 1-month lag period. In addition, an association with norovirus was observed in patients aged over 20 years, and with influenza virus (IFV) in patients aged over 60 years. This study found that HRSV, HCoV, IFV, and norovirus tended to precede encephalitis by 1 month. Further research is required to confirm the association between these viruses and encephalitis.

Complications Associated with Foodborne Listeriosis: A Scoping Review

Listeria monocytogenes is a relatively rare but highly pathogenic bacterium that can cause foodborne infections. In the United States there are ∼1600 cases per year, 94% of which result in hospitalizations and 20% in deaths. Per-case burden is high because the disease also causes serious complications, including sepsis, encephalitis, meningitis, miscarriage, and stillbirth. The disease burden of L. monocytogenes is underestimated because some of these acute complications can also result in long-term outcomes. In this article, we conducted a scoping review of L. monocytogenes complications and longer term outcomes from articles published between 2000 and 2018. Search terms were developed for four major databases (PubMed, Scopus, Web of Science, and Embase) as well as gray literature and hand searches of review articles. We follow standard scoping review methodology and assessment. Out of 10,618 unique articles originally identified, 115 articles were included, representing 49 unique outcomes. The majority of studies were cohort designs (n = 67) and conducted in the United States or Europe (n = 98). Four major outcome groupings were death, neurological disorders, sepsis, and congenital infection. This study identifies substantial research on the common acute complications of L. monocytogenes and few long-term consequences of L. monocytogenes. We identify the need for additional studies to determine the longer term impacts of these acute complications.

Healthcare resource utilisation pattern and costs associated with herpes simplex virus diagnosis and management: a systematic review

OBJECTIVES

Little is known about the economic burden of herpes simplex virus (HSV) across countries. This article aims to summarise existing evidence on estimates of costs and healthcare resource utilisation associated with genital and neonatal HSV infection.

DESIGN

Systematic literature review.

DATA SOURCES

Seven databases were searched from inception to 31 August 2020. A focused search was performed to supplement the results.

ELIGIBILITY CRITERIA

Studies which reported either healthcare resource utilisation or costs associated with HSV-related healthcare, including screening, diagnosis and treatment of genital HSV infection and neonatal herpes prevention and treatment.

DATA EXTRACTION AND SYNTHESIS

Two independent reviewers extracted data and assessed the risk of bias using the Larg and Moss's checklist. All data were summarised narratively.

RESULTS

Out of 11 443 articles, 38 were included. Most studies (35/38, 94.6%) were conducted in high-income countries, primarily the United States, and were more often related to the prevention or management of neonatal herpes (n=21) than HSV genital ulcer disease (n=17). Most analyses were conducted before 2010. There was substantial heterogeneity in the reporting of HSV-related healthcare resource utilisation, with 74%-93% individuals who sought care for HSV, 11.6%-68.4% individuals who received care, while neonates with herpes required a median of 6-34 hospitalisation days. The costs reported were similarly heterogeneous, with wide variation in methodology, assumptions and outcome measures between studies. Cost for screening ranged from US$7-100, treatment ranged from US$0.53-35 for an episodic therapy, US$240-2580 yearly for suppressive therapy, while hospitalisation for neonatal care ranged from US$5321-32 683.

CONCLUSIONS

A paucity of evidence exists on healthcare resource utilisation and costs associated with HSV infection, especially among low-income and middle-income countries. Future research is needed on costs and healthcare utilisation patterns to improve overall understanding of the global economic burden of HSV.

Measuring complications of serious pediatric emergencies using ICD-10

OBJECTIVE

To create definitions for complications for 16 serious pediatric conditions using the International Classification of Diseases, 10th Revision, Clinical Modification or Procedure Coding System (ICD-10-CM/PCS), and to assess whether complication rates are similar to those measured with ICD-9-CM/PCS.

DATA SOURCES

The Healthcare Cost and Utilization Project State Emergency Department and Inpatient Databases from five states between 2014 and 2017 were used to identify cases and assess complication rates. Incidences were calculated using population counts from the 5-year American Community Survey.

DATA COLLECTION/EXTRACTION METHODS

Patients were identified by the presence of a diagnosis code for one of the 16 serious conditions. Only the first encounter for a given condition by a patient was included. Encounters resulting in transfer were excluded as the presence of complications was unknown.

STUDY DESIGN

We defined complications using data elements routinely available in administrative databases including ICD-10-CM/PCS codes. The definitions were adapted from ICD-9-CM/PCS using general equivalence mappings and refined using consensus opinion. We included 16 serious conditions: appendicitis, bacterial meningitis, compartment syndrome, new-onset diabetic ketoacidosis (DKA), ectopic pregnancy, empyema, encephalitis, intussusception, mastoiditis, myocarditis, orbital cellulitis, ovarian torsion, sepsis, septic arthritis, stroke, and testicular torsion. Using data from children under 18 years, we compared incidences and complication rates across the ICD-10-CM/PCS transition for each condition using interrupted time series.

PRINCIPAL FINDINGS

There were 61 314 ED visits for a serious condition; the most common was appendicitis (n = 37 493). Incidence rates for each condition were not significantly different across the ICD-10-CM/PCS transition for 13/16 conditions. Three differed: empyema (increased 42%), orbital cellulitis (increased 60%), and sepsis (increased 26%). Complication rates were not significantly different for each condition across the ICD-10-CM/PCS transition, except appendicitis (odds ratio 0.62, 95% CI 0.57-0.68), DKA (OR 3.79, 95% CI 1.92-7.50), and orbital cellulitis (OR 0.53, 95% CI 0.30-0.95).

CONCLUSIONS

For most conditions, incidences and complication rates were similar before and after the transition to ICD-10-CM/PCS codes, suggesting our system identifies complications of conditions in administrative data similarly using ICD-9-CM/PCS and ICD-10-CM/PCS codes. This system may be applied to screen for cases with complications and in health services research.

Predicting Inpatient Mortality Among Encephalitis Patients: A Novel Admission Risk Score

Background

Identifying underlying commonalities among all-cause encephalitis cases can be extraordinarily useful in predicting meaningful risk factors associated with inpatient mortality.

Methods

A retrospective cohort of patients with encephalitis was derived from a clinical chart review of adult patients (age ≥18 years) across 16 different hospitals in Houston, Texas, between January 2005 and July 2015. Clinical features at admission were assessed for their correlation with inpatient mortality and used to derive a final risk score prediction tool.

Results

The study included a total of 273 adult patients with all-cause encephalitis, 27 (9.9%) of whom died during hospitalization. A limited number of clinical features were substantially different between patients who survived and those who died (Charlson score, Glasgow coma scale [GCS], immunosuppression, fever on admission, multiple serologic studies, and abnormal imaging). A final multivariable logistic model was derived with the following risk factors, which were transformed into a scoring system: 1 point was assigned to the presence of a Charlson score >2, thrombocytopenia, or cerebral edema, and 2 points for a GCS value <8. Patients were then classified into different risk groups for inpatient mortality: 0 points (0%), 1 point (7%), 2 points (10.9%), 3 points (36.8%), and ≥4 points (81.8%).

Conclusions

The risk score developed from this study shows a high predictive value. This can be highly beneficial in alerting care providers to key clinical risk factors associated with in-hospital mortality in adults with encephalitis.

The longitudinal health economic impact of viral encephalitis in the United States

Introduction. Previous studies of viral encephalitis have focused on acute costs, estimating incidence at 7.3 per 100 000 and total US annual charges at $2 billion in 2010.Aim. We aim to quantify the most updated longitudinal health economic impact of viral encephalitis in the USA from 2008 to 2015.Methodology. Data on patients diagnosed with viral encephalitis were obtained from the Truven Health Analytics MarketScan database. Patients with a primary diagnosis of viral encephalitis, from herpetic viruses and other viral aetiologies (e.g. West Nile fever) were included in the analysis. Data concerning healthcare resource utilization, inpatient mortality, length of stay and accrued healthcare costs were collected for up to 5 years.Results. Among 3985 patients with continuous enrolment for 13 months prior to the encephalitis diagnosis, more non-herpes simplex encephalitis (61.7 %) than herpes simplex encephalitis (HSE; 38.3 %) cases were recorded, with the majority concentrated in the southern USA (29.2 %). One-year inpatient mortality was 6.2 %, which over a 5-year period rose to 8.9 % for HSE and 5.8 % for all other viral encephalitides. HSE resulted in longer cumulative stays in the hospital (11 days vs. 4 days; P=0.0025), and accrued 37 % higher first-year costs, after adjusting for known confounders [P<0.001, cost ratio=1.37, 95 % confidence interval (1.20, 1.57)]. Additionally, HSE was associated with greater 5-year cumulative median charges ($125 338 vs. $82 317, P=0.0015).Conclusion. The health economic impact and long-term morbidity of viral encephalitis in the USA are substantial.

Clinical Features, Diagnosis, and Outcome of Encephalitis in French Guiana

The aim of our study was to describe the clinical features, the etiologies, and the factors associated with poor outcome of encephalitis in French Guiana. Our study was retrospective, including all cases of encephalitis hospitalized in the Cayenne General Hospital, from January 2007 to July 2017. Patients were included through the 2013 encephalitis consortium criteria and the outcome was evaluated using the Glasgow outcome scale at 3 months from the diagnosis of encephalitis. We included 108 patients, giving an approximate incidence rate of four cases/100,000 inhabitants/year. The origin of the encephalitis was diagnosed in 81 cases (75%), and 72 of them (66.7%) were from an infectious origin. The most common infectious causes were Cryptococcus sp. (18.5%) independently of the immune status, Toxoplasma gondii (13.9%), and Streptococcus pneumoniae (5.5%). In the follow-up, 48 patients (46.6%) had poor outcome. Independent risk factors associated with poor outcome at 3 months were “coming from inside area of the region” (P = 0.036, odds ratio [OR] = 4.19; CI 95% = 1.09–16.06), need for mechanical ventilation (P = 0.002, OR = 5.92; CI 95% = 1.95–17.95), and age ≥ 65 years (P = 0.049, OR = 3.99; CI 95% = 1.01–15.89). The most identified cause of encephalitis in French Guiana was Cryptococcus. The shape of the local epidemiology highlights the original infectious situation with some local specific pathogens.

Clinico-epidemiological Study of Viral Acute Encephalitis Syndrome Cases and Comparison to Nonviral Cases in Children from Eastern India

Objectives:

The objective is to study the clinico-epidemiological features of viral acute encephalitis syndrome (AES) cases and compare them with nonviral AES cases in children from Eastern India.

Methods:

This prospective observational study was conducted in the department of pediatrics of a tertiary care teaching hospital in Eastern India over 18-month period. Children (6 months to 15 years) with acute onset of fever (≥37.5°C) and a change in mental status (including symptoms such as confusion, disorientation, coma, or inability to talk) and/or new onset of seizures (excluding simple febrile seizures) were included in the study. The main outcome measures were the etiology and proportion attributed to viruses causing AES with clinical correlation.

Results:

Of 834 of clinically suspected AES cases, viral etiology could be confirmed in 136 (16.3%) cases (herpes simplex virus-1 [HSV-I] was most common). The 5–15 years' age group was most commonly affected (boys > girls). More cases occurred from July to November. The presence of rash and Glasgow Coma Scale <8 at admission was significantly higher in viral AES. During hospitalization, development of shock, ventilatory requirement, duration of stay, and mortality was significantly higher in viral AES. On neuroimaging, global cerebral injury was common in HSV, Japanese encephalitis, and varicella-virus AES.

Conclusions:

Viral etiology forms a significant proportion of pediatric AES. Morbidity and mortality are high in viral compared to nonviral AES. Herpes encephalitis (HSV-I) is the most common cause of pediatric AES in Eastern India. Viral AES has poor prognosis compared to nonviral AES.

National epidemiological study reveals longer paediatric bone and joint infection stays for infants and in general hospitals

AIM

Published studies have suggested that two to five days of intravenous treatment could effectively treat paediatric bone and joint infections (PBJI), allowing a faster discharge. This study analysed the factors associated with PBJI hospital stays lasting longer than five days using the French National Hospital Discharge Database.

METHODS

We selected children under 15 years hospitalised in 2013 with haematogenous PBJIs using a validated French algorithm based on specific diagnosis and surgical procedure codes. Risk factors for stays of more than five days were analysed using logistic regression.

RESULTS

In 2013, 2717 children were hospitalised for PBJI, with 49% staying more than five days. The overall incidence of 22 per 100 000, was highest in males and toddlers. The main causes were septic arthritis (50%) and osteomyelitis (46%) and 50% of the pathogens were Staphylococci. The odd ratios for stays of five days or more were infancy, coded bacteria and sickle cell disease (7.0), having spondylodiscitis rather than septic arthritis (2.2) and being hospitalised in a general hospital rather than a teaching hospital (1.6).

CONCLUSION

Half of the hospital stays exceeded five days, despite scientific evidence supporting a shorter intravenous antibiotherapy regimen. Greater knowledge and widespread use of short treatment regimens are needed.

[The use of administrative health databases in infectious disease epidemiology and public health]

BACKGROUND

The public health burden resulting from infectious diseases requires efforts in surveillance and evaluation of health care. The use of administrative health databases (AHD) and in particular the French national health insurance database (SNIIRAM) is an opportunity to improve knowledge in this field. The SNIIRAM data network (REDSIAM) workshop dedicated to infectious diseases conducted a narrative literature review of studies using French AHD. From the results, benefits and limits of these new tools in the field of infectious diseases are presented.

METHODS

Publications identified by the members of the workgroup were collected using an analytical framework that documented the pathology of interest, the aim of the study, the goal of the developed algorithm, the kind of data, the study period, and the presence of an evaluation or a discussion of the performance of the performed algorithm.

RESULTS

Fifty-five articles were identified. A majority focused on the field of vaccination coverage and joint infections. Excluding vaccine coverage field, the aim of 28 studies was epidemiological surveillance. Twenty-six studies used hospital databases exclusively, 18 used ambulatory databases exclusively and 4 used both. Validation or discussion of the performed algorithm was present in 18 studies.

CONCLUSIONS

The literature review confirmed the interest of the French AHD in the infectious diseases field. The AHD are additional tools of the existing surveillance systems and their use will probably be more frequent in the coming years given their advantage and reliability. However, incoming users need to be assisted. Thus, the workgroup will contribute to a reasonable use of AHD and support future developments.

A Feasibility Study of Quantifying Longitudinal Brain Changes in Herpes Simplex Virus (HSV) Encephalitis Using Magnetic Resonance Imaging (MRI) and Stereology

OBJECTIVES

To assess whether it is feasible to quantify acute change in temporal lobe volume and total oedema volumes in herpes simplex virus (HSV) encephalitis as a preliminary to a trial of corticosteroid therapy.

METHODS

The study analysed serially acquired magnetic resonance images (MRI), of patients with acute HSV encephalitis who had neuroimaging repeated within four weeks of the first scan. We performed volumetric measurements of the left and right temporal lobes and of cerebral oedema visible on T2 weighted Fluid Attenuated Inversion Recovery (FLAIR) images using stereology in conjunction with point counting.

RESULTS

Temporal lobe volumes increased on average by 1.6% (standard deviation (SD 11%) in five patients who had not received corticosteroid therapy and decreased in two patients who had received corticosteroids by 8.5%. FLAIR hyperintensity volumes increased by 9% in patients not receiving treatment with corticosteroids and decreased by 29% in the two patients that had received corticosteroids.

CONCLUSIONS

This study has shown it is feasible to quantify acute change in temporal lobe and total oedema volumes in HSV encephalitis and suggests a potential resolution of swelling in response to corticosteroid therapy. These techniques could be used as part of a randomized control trial to investigate the efficacy of corticosteroids for treating HSV encephalitis in conjunction with assessing clinical outcomes and could be of potential value in helping to predict the clinical outcomes of patients with HSV encephalitis.

Pilot surveillance for childhood encephalitis in Australia using the Paediatric Active Enhanced Disease Surveillance (PAEDS) network

We aimed to assess the performance of active surveillance for hospitalized childhood encephalitis in New South Wales (NSW) using the Paediatric Active Enhanced Disease Surveillance (PAEDS) network to inform methodology for the nationwide Australian childhood encephalitis (ACE) study. We piloted active surveillance for suspected encephalitis from May to December 2013 at the Children's Hospital at Westmead, Sydney, NSW. Cases were ascertained using four screening methods: weekday nurse screening of admission records (PAEDS), cerebrospinal fluid (CSF) microscopy records, magnetic resonance imaging (MRI) reports, and pharmacy dispensing records. Comprehensive clinical data were prospectively collected on consented participants and subsequently reviewed by an expert panel. Cases were categorized as confirmed encephalitis or 'not encephalitis'; encephalitis cases were sub-categorized as infectious, immune-mediated or unknown. We performed an ICD-10 diagnostic code audit of hospitalizations for the pilot period. We compared case ascertainment in the four screening methods and with the ICD code audit. Forty-eight cases of suspected encephalitis were identified by one or more methods. PAEDS was the most efficient mechanism (yield 34%), followed by MRI, CSF, and pharmacy audits (yield 14%, 12%, and 7% respectively). Twenty-five cases met the criteria for confirmed encephalitis. PAEDS was the most sensitive of the mechanisms for confirmed encephalitis (92%) with a positive predictive value (PPV) of 72%. The ICD audit was moderately sensitive (64%) but poorly specific (Sp 9%, PPV 14%). Of the 25 confirmed encephalitis cases, 19 (76%) were sub-categorized as infectious, three (12%) were immune-mediated, and three (12%) were 'unknown'. We identified encephalitis cases associated with two infectious disease outbreaks (enterovirus 71, parechovirus 3). PAEDS is an efficient, sensitive and accurate surveillance mechanism for detecting cases of childhood encephalitis including those associated with emerging infectious diseases. Active surveillance significantly increases the ascertainment of encephalitis cases compared with passive approaches.

Epidemiology and outcomes of acute encephalitis

PURPOSE OF REVIEW

This review seeks to describe recent advances in the epidemiology, outcomes, and prognostic factors in acute encephalitis.

RECENT FINDINGS

Infectious causes continue to account for the largest proportion of encephalitis cases in which a cause is identified, although autoimmune causes are increasingly recognized. Type-A gamma-aminobutyric acid (GABAa) receptor antibodies have been recently identified in encephalitis with refractory seizures, whereas the roles of antibodies to the glycine receptor and dipeptidyl peptidase-like protein 6 have been defined in progressive encephalomyelitis with rigidity and myoclonus. Recent findings in the US cases of encephalomyelitis presenting with acute flaccid paralysis raise the possibility that enterovirus D68, a common respiratory pathogen, may cause central nervous system disease. Mortality from acute encephalitis occurs in about 10% of cases, with a large proportion of survivors suffering from cognitive or physical disability. In addition to delay in institution of appropriate antiviral or immune therapy, several potentially reversible factors associated with poor prognosis have been identified, including cerebral edema, status epilepticus, and thrombocytopenia.

SUMMARY

Encephalitis imposes a significant worldwide health burden and is associated with poor outcomes. Supportive treatment and early institution of therapy may improve outcomes. Careful neurocognitive assessment of survivors of encephalitis is needed to better define long-term outcomes.

Adult encephalitis surveillance: experiences from an Australian prospective sentinel site study

Few countries routinely collect comprehensive encephalitis data, yet understanding the epidemiology of this condition has value for clinical management, detecting novel and emerging pathogens, and guiding timely public health interventions. When this study was conducted there was no standardized diagnostic algorithm to aid identification of encephalitis or systematic surveillance for adult encephalitis. In July 2012 we tested three pragmatic surveillance options aimed at identifying possible adult encephalitis cases admitted to a major Australian hospital: hospital admissions searches, clinician notifications and laboratory test alerts (CSF herpes simplex virus requests). Eligible cases underwent structured laboratory investigation and a specialist panel arbitrated on the final diagnosis. One hundred and thirteen patients were initially recruited into the 10-month study; 20/113 (18%) met the study case definition, seven were diagnosed with infectious or immune-mediated encephalitis and the remainder were assigned alternative diagnoses. The laboratory alert identified 90% (102/113) of recruited cases including six of the seven cases of confirmed encephalitis suggesting that this may be a practical data source for case ascertainment. The application of a standardized diagnostic algorithm and specialist review by an expert clinical panel aided diagnosis of patients with encephalitis.

Long-term outcome of severe herpes simplex encephalitis: a population-based observational study

Introduction

Herpes simplex encephalitis (HSE) is a rare disease with a poor prognosis. No recent evaluation of hospital incidence, acute mortality and morbidity is available. In particular, decompressive craniectomy has rarely been proposed in cases of life-threatening HSE with temporal herniation, in the absence of evidence. This study aimed to assess the hospital incidence and mortality of HSE, and to evaluate the characteristics, management, the potential value of decompressive craniectomy and the outcome of patients with HSE admitted to intensive care units (ICUs).

Methods

Epidemiological study: we used the hospital medical and administrative discharge database to identify hospital stays, deaths and ICU admissions relating to HSE in 39 hospitals, from 2010 to 2013. Retrospective monocentric cohort: all patients with HSE admitted to the ICU of the university hospital during the study were included. The use of decompressive craniectomy and long-term outcome were analyzed. The initial brain images were analyzed blind to outcome.

Results

The hospital incidence of HSE was 1.2/100,000 inhabitants per year, 32 % of the patients were admitted to ICUs and 17 % were mechanically ventilated. Hospital mortality was 5.5 % overall, but was as high as 11.9 % in ICUs. In the monocentric cohort, 87 % of the patients were still alive after one year but half of them had moderate to severe disability. Three patients had a high intracranial pressure (ICP) with brain herniation and eventually underwent decompressive hemicraniectomy. The one-year outcome of these patients did not seem to be different from that of the other patients. It was not possible to predict brain herniation reliably from the initial brain images.

Conclusions

HSE appears to be more frequent than historically reported. The high incidence we observed probably reflects improvements in diagnostic performance (routine use of PCR). Mortality during the acute phase and long-term disability appear to be stable. High ICP and brain herniation are rare, but must be monitored carefully, as initial brain imaging is not useful for identifying high-risk patients. Decompressive craniectomy may be a useful salvage procedure in cases of intractable high ICP.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1046-y) contains supplementary material, which is available to authorized users.

Encephalitis hospitalization rates and inpatient mortality in the United States, 2000-2010

Background

Encephalitis rates by etiology and acute-phase outcomes for encephalitis in the 21^st century are largely unknown. We sought to evaluate cause-specific rates of encephalitis hospitalizations and predictors of inpatient mortality in the United States.

Methods

Using the Nationwide Inpatient Sample (NIS) from 2000 to 2010, a retrospective observational study of 238,567 patients (mean [SD] age, 44.8 [24.0] years) hospitalized within non-federal, acute care hospitals in the U.S. with a diagnosis of encephalitis was conducted. Hospitalization rates were calculated using population-level estimates of disease from the NIS and population estimates from the United States Census Bureau. Adjusted odds of mortality were calculated for patients included in the study.

Results

In the U.S. from 2000–2010, there were 7.3±0.2 encephalitis hospitalizations per 100,000 population (95% CI: 7.1–7.6). Encephalitis hospitalization rates were highest among females (7.6±0.2 per 100,000) and those <1 year and >65 years of age with rates of 13.5±0.9 and 14.1±0.4 per 100,000, respectively. Etiology was unknown for approximately 50% of cases. Among patients with identified etiology, viral causes were most common (48.2%), followed by Other Specified causes (32.5%), which included predominantly autoimmune conditions. The most common infectious agents were herpes simplex virus, toxoplasma, and West Nile virus. Comorbid HIV infection was present in 7.7% of hospitalizations. Average length of stay was 11.2 days with mortality of 5.6%. In regression analysis, patients with comorbid HIV/AIDS or cancer had increased odds of mortality (odds ratio [OR]  = 1.70; 95% CI: 1.30–2.22 and OR = 2.26; 95% CI: 1.88–2.71, respectively). Enteroviral, postinfectious, toxic, and Other Specified causes were associated with lower odds vs. herpes simplex encephalitis.

Conclusions

While encephalitis and encephalitis-related mortality impose a considerable burden in the U.S. in the 21^st Century, the reported demographics of hospitalized encephalitis patients may be changing.

Encephalitis-associated hospitalizations among American Indians and Alaska Natives

Encephalitis produces considerable morbidity in the United States, but morbidity rates among American Indian/Alaska Native (AI/AN) people have not been described. Hospitalization records listing an encephalitis diagnosis were analyzed by using Indian Health Service direct/contract inpatient data. For 1998-2010, there were 436 encephalitis-associated hospitalizations among AI/AN people, an average annual age-adjusted hospitalization rate of 3.1/100,000 population. The rate for infants (11.9) was more than double that for any other age group. Death occurred for 4.1% of hospitalizations. Consistent with reports for the general U.S. population, the rate was high among infants and most (53.9%) hospitalizations were of unexplained etiology. The average annual rate during the study period appeared lower than for the general U.S. population, due particularly to lower rates in the elderly. Future community-based surveillance and mortality studies are needed to confirm these findings and examine reasons underlying the low rates of encephalitis in AI/AN people.