Characteristics and long-term prognosis of Danish patients with varicella zoster virus detected in the cerebrospinal fluid, compared with the background population

Current epidemiology of infectious encephalitis: a narrative review

BACKGROUND

Infectious encephalitis poses a global health challenge with high mortality and severe neurological consequences in survivors. Emerging pathogens and outbreaks are reshaping the patterns of the disease.

OBJECTIVES

The objective of this study is to understand the current epidemiology for improving prevention, diagnosis, and treatment.

SOURCES

Medline/PubMed was searched using 'encephalitis' and related MeSH terms from 2020 to September 2024. Population-based and case-control studies on encephalitis were searched without time restrictions. Other studies known by the authors were also included.

CONTENT

The incidence of infectious encephalitis ranged from 1.4 to 13.8 cases per 100 000 per year with a bimodal peak in infants and older adults. Herpes viruses remain the most common causes of sporadic encephalitis with herpes simplex virus type 1 and varicella zoster virus reported most frequently. In endemic regions, arboviruses such as Japanese encephalitis virus and West Nile virus contribute significantly to the disease burden. Climate change is adding to the spread of these vector-borne viruses thereby both altering the geographical distribution of causative agents and increasing the frequency of outbreaks. Evidence on risk factors associated with encephalitis is scarce and hampered by the absence of population-based case-control studies. The prognosis of infectious encephalitis remains unchanged during recent decades with high case-fatality rates and may vary according to, e.g. aetiology, age, and presence of immunocompromising conditions or other comorbidities. Importantly, a substantial proportion of survivors are left with disabling neurological sequelae.

IMPLICATIONS

The findings underscore the importance of public health surveillance and prevention strategies to address the changing epidemiology of encephalitis. This can be pursued through vaccination programmes and vector control efforts. Future research should focus on identifying risk factors, improving diagnostic tools, optimizing current treatment as well as exploring novel therapies for patients with encephalitis. Timely treatment and specialised post-hospital rehabilitation remain essential for patient management.

Incidence and Risk Factors for Varicella-Zoster Virus-Associated Central Nervous System Infections: A Nationwide Swedish Retrospective Case-Control Study

The determinants of varicella-zoster virus (VZV)-associated central nervous system (CNS) infection have not been fully elucidated. This study aimed to investigate the incidence and risk factors, including immunosuppression, for different manifestations of VZV-associated CNS infection. Patient registers were used to include adults diagnosed with VZV-associated CNS infections between 2010 and 2019 in Sweden. Nationwide registers covering specialized care, and regional registers covering primary care, were used. Controls without a VZV diagnosis during the study period were matched by age and sex. Risk factors were calculated using multivariable logistic regression. A total of 1488 adult cases with VZV-associated CNS infection were identified, yielding an incidence of 1.92/100 000 person-years, which increased over the study period. Meningitis was the most frequent (45%), followed by encephalitis (38%), and Ramsay Hunt syndrome (17%). The highest incidence was observed in individuals over 70 years of age (4.15/100 000 person-years), in whom encephalitis was most common. Statistically significant risk factors for VZV-associated CNS infection were HIV, hematological cancer, treatment with specific immunosuppressants or glucocorticoids, chronic obstructive pulmonary disease, diabetes, solid cancer, stroke, and congestive heart failure. Encephalitis was associated with older age, more immunosuppressive conditions, and more comorbidities than other manifestations. In conclusion, VZV is a common cause of adult viral CNS infection, for which elderly individuals with immunosuppressive or comorbid conditions are at the highest risk. The strongest risk factors found were HIV, hematological cancer, and treatment with specific immunosuppressants or high-dose glucocorticoids.

Increase in Adult Patients with Varicella Zoster Virus-Related Central Nervous System Infections, Japan

An increase in the number of herpes zoster patients has been reported since universal varicella immunization was introduced, perhaps because of reduced opportunities for varicella patients to experience the natural booster effect caused by reexposure. We investigated recent trends of varicella zoster virus (VZV)-related central nervous system (CNS) infections at a university hospital in Japan. We enrolled patients with suspected CNS infection during 2013-2022 and tested cerebrospinal fluid samples by real-time PCR for DNA from 7 human herpesviruses. VZV DNA was the most commonly detected in 62 (10.2%) of 615 patients. Kulldorff's circular spatial scan statistics demonstrated a significant temporal cluster of patients with VZV-related CNS infections during 2019-2022 (p = 0.008). Among persons with such infections, the percentage with aseptic meningitis was significantly higher during 2019-2022 (86.8%), when the temporal cluster of cases occurred, than during 2013-2018 (50.0%) (p = 0.0029).

The association between varicella zoster virus and dementia: a systematic review and meta-analysis of observational studies

PURPOSE

The relationship between varicella zoster virus (VZV) infection and the risk of dementia has not been previously studied specifically. Therefore, this study sought to determine the relationship between studying VZV infection and dementia occurring in the general population by conducting an extensive meta-analysis of published cases.

METHOD

A systematic literature search was conducted in seven online databases by October 31, 2022. Heterogeneity was tested by the I2 index. Pooled HR and 95% CI were used to estimate the effect of VZV infection on dementia. Sensitivity analyses and publication bias were also performed.

RESULT

Nine studies involving 3,326,673 subjects were included. VZV infection was associated with an increased risk of dementia (HR = 1.11, 95% CI: 1.02-1.21). The risk of dementia was reduced in those who received antiviral therapy compared to those who did not (HR = 0.84, 95% CI: 0.71-0.99). In addition, VZV infection was found to be associated with an increased risk of developing dementia in the pooled results of the moderate quality study (HR = 1.81,95% CI: 1.27-2.59), and this association persisted when subgroup analyses were performed based on region (Asia: HR = 1.18,95% CI: 1.04-1.33).

CONCLUSIONS

Our results suggest that VZV infection might increase the risk of developing dementia, but there is no clear mechanism about the true relationship, and since there is no effective treatment for dementia, and our results suggest that some populations can benefit from antiviral therapy, it is at least arguable that patients who develop VZV infection should be treated with appropriate antiviral medications.

Can we forecast poor outcome in herpes simplex and varicella zoster encephalitis? A narrative review

Herpes simplex virus (HSV) and varicella zoster virus (VZV) are among the most commonly diagnosed infectious causes of sporadic encephalitis worldwide. Despite treatment, mortality and morbidity rates remain high, especially for HSV encephalitis. This review is intended to provide an overview of the existing scientific literature on this topic from the perspective of a clinician who is confronted with serious decisions about continuation or withdrawal of therapeutic interventions. We performed a literature review searching two databases and included 55 studies in the review. These studies documented or investigated specifically outcome and predictive parameters of outcome of HSV and/or VZV encephalitis. Two reviewers independently screened and reviewed full-text articles meeting the inclusion criteria. Key data were extracted and presented as a narrative summary. Both, HSV and VZV encephalitis have mortality rates between 5 and 20% and complete recovery rates range from 14 to 43% for HSV and 33 to 49% for VZV encephalitis. Prognostic factors for both VZV and HSV encephalitis are older age and comorbidity, as well as severity of disease and extent of magnetic resonance imaging (MRI) lesions on admission, and delay in treatment initiation for HSV encephalitis. Although numerous studies are available, the main limiting factors are the inconsistent patient selection and case definitions as well as the non-standardised outcome measures, which hampers the comparability of the studies. Therefore, larger and standardised observational studies applying validated case definitions and outcome measures including quality of life assessment are required to provide solid evidence to answer the research question.

Risk of Psychiatric Disorders, Use of Psychiatric Hospitals, and Receipt of Psychiatric Medication in Patients With Brain Abscess in Denmark

BACKGROUND

It is unknown whether patients diagnosed with brain abscess have an increased risk of psychiatric disorders.

METHODS

In this nationwide, population-based matched cohort study from Denmark, we compared the incidence of psychiatric disorders, use of psychiatric hospitals, and receipt of psychiatric medications between patients diagnosed with brain abscess and individuals from the general population, matched on date of birth, sex, and residential area.

RESULTS

We included 435 patients diagnosed with brain abscess and 3909 individuals in the comparison cohort: 61% were male and median age was 54 years. Patients diagnosed with brain abscess were more likely to suffer from comorbidity. The risk of a hospital diagnosis of psychiatric disorders was increased the first 5 years of observation. In the subpopulation, who had never been in contact with psychiatric hospitals or received psychiatric medication before study inclusion, the risk of developing psychiatric disorders was close to that of the background population, especially when we excluded dementia from this outcome. There was a substantial increase in the receipt of anxiolytics and antidepressants. The difference in the proportion of individuals who received anxiolytics and antidepressants increased from 4% (95% confidence interval [CI], 0%-7%) and 2% (95% CI, -1% to 5%) 2 years before study inclusion to 17% (95% CI, 12%-21%) and 11% (95% CI, 7%-16%) in the year after study inclusion.

CONCLUSIONS

Patients with brain abscess without prior psychiatric disorders or receipt of psychiatric medicine are not at increased risk psychiatric disorders diagnosed in psychiatric hospitals, but they have an increased receipt of psychiatric medication.

Incident Herpes Zoster and Risk of Dementia: A Population-Based Danish Cohort Study

BACKGROUND AND OBJECTIVES

Herpes zoster (HZ) is caused by reactivation of the neurotrophic varicella-zoster virus (VZV). Zoster may contribute to development of dementia through neuroinflammation, cerebral vasculopathy, or direct neural damage, but epidemiologic evidence is limited. We used data from linked nationwide Danish registries to conduct a cohort study of the association between zoster and dementia during 1997-2017. As secondary aims, we examined whether associations were more pronounced for zoster involving cranial nerves (mainly ophthalmic zoster) or the CNS and Alzheimer disease as an outcome.

METHODS

We included people aged ≥40 years with zoster and a general population comparison cohort matched 5:1 by sex and birth year. We identified zoster and dementia in the registries using prescription records in the community and hospital diagnoses. We used Cox regression to compute confounder-adjusted hazard ratios (HRs) with 95% CIs for dementia associated with zoster during 0-1 year and 1-21 years of follow-up. We compared the cumulative incidence of dementia, inverse probability weighted for confounders.

RESULTS

The study included 247,305 people with zoster and 1,235,890 matched general population comparators (median age 64 years; 61% female). The HR of all-cause dementia was 0.98 (95% CI 0.92-1.04) during the first year and 0.93 (95% CI 0.90-0.95) thereafter in people with zoster vs matched comparators. Dementia was diagnosed in 9.7% of patients with zoster and 10.3% of matched comparators by the end of follow-up. We observed no increased long-term risk of dementia in subgroup analyses, except possibly in people with CNS infection (HR 1.94; 95% CI 0.78-4.80). Analyses of Alzheimer disease as a separate outcome showed similar results.

DISCUSSION

HZ is not associated with an increased risk of dementia, and contrary to expectation, we found a small decrease in the risk. The explanation for this finding is unclear, and systematic errors should be considered. Patients with CNS involvement had an almost 2-fold increased relative risk of dementia. The population attributable fraction of dementia due to this rare complication is estimated at 0.014%. Therefore, universal vaccination against VZV in the elderly is unlikely to reduce dementia risk.

Existing Data Sources for Clinical Epidemiology: The Danish Study Group of Infections of the Brain Database (DASGIB)

Central nervous system (CNS) infections are rare diseases that are associated with considerable morbidity and mortality. Increased knowledge based on contemporary data is a prerequisite for improved management and prevention of these serious conditions. Yet, population-based databases of patients hospitalized with CNS infections remain scarce. The Danish Study Group of Infections of the Brain (DASGIB) has prospectively registered information on all adults ≥18 years of age admitted with CNS infections at departments of infectious diseases in Denmark since 2015. The main variables collected are baseline demographics, blood and cerebrospinal fluid tests, imaging results, and outcome using the Glasgow Outcome Scale score. To investigate important aspects for each type of CNS infections, additional variables are included specifically for bacterial meningitis, viral meningitis, encephalitis, brain abscess, neurosyphilis, and Lyme neuroborreliosis. From 2015 to 2020, a total of 3579 cases of CNS infections have been recorded in the DASGIB database. Using the unique civil registration number assigned to all Danish residents, the database can be unambiguously linked with nationwide healthcare registries at the individual level. This enables researchers to conduct detailed population-based and longitudinal observational studies of risk and prognosis of CNS infections and to compare them with matched population cohorts. The database is well-suited for epidemiological research and the DASGIB network forms a solid infrastructure for future national and international collaborations.