Comparison of the epidemiological and clinical features of tick-borne encephalitis in children and adults

Tick-Borne Encephalitis Vaccine: Recommendations of the Advisory Committee on Immunization Practices, United States, 2023

Tick-borne encephalitis (TBE) virus is focally endemic in parts of Europe and Asia. The virus is primarily transmitted to humans by the bites of infected

Ixodes species ticks but can also be acquired less frequently by alimentary transmission. Other rare modes of transmission include through breastfeeding, blood transfusion, solid organ transplantation, and slaughtering of viremic animals. TBE virus can cause acute neurologic disease, which usually results in hospitalization, often permanent neurologic or cognitive sequelae, and sometimes death. TBE virus infection is a risk for certain travelers and for laboratory workers who work with the virus. In August 2021, the Food and Drug Administration approved Ticovac TBE vaccine for use among persons aged ≥1 year. This report summarizes the epidemiology of and risks for infection with TBE virus, provides information on the immunogenicity and safety of TBE vaccine, and summarizes the recommendations of the Advisory Committee on Immunization Practices (ACIP) for use of TBE vaccine among U.S. travelers and laboratory workers.

The risk for TBE for most U.S. travelers to areas where the disease is endemic is very low. The risk for exposure to infected ticks is highest for persons who are in areas where TBE is endemic during the main TBE virus transmission season of April–November and who are planning to engage in recreational activities in woodland habitats or who might be occupationally exposed. All persons who travel to areas where TBE is endemic should be advised to take precautions to avoid tick bites and to avoid the consumption of unpasteurized dairy products because alimentary transmission of TBE virus can occur. TBE vaccine can further reduce infection risk and might be indicated for certain persons who are at higher risk for TBE. The key factors in the risk-benefit assessment for vaccination are likelihood of exposure to ticks based on activities and itinerary (e.g., location, rurality, season, and duration of travel or residence). Other risk-benefit considerations should include 1) the rare occurrence of TBE but its potentially high morbidity and mortality, 2) the higher risk for severe disease among certain persons (e.g., older persons aged ≥60 years), 3) the availability of an effective vaccine, 4) the possibility but low probability of serious adverse events after vaccination, 5) the likelihood of future travel to areas where TBE is endemic, and 6) personal perception and tolerance of risk

ACIP recommends TBE vaccine for U.S. persons who are moving or traveling to an area where the disease is endemic and will have extensive exposure to ticks based on their planned outdoor activities and itinerary. Extensive exposure can be considered based on the duration of travel and frequency of exposure and might include shorter-term (e.g., <1 month) travelers with daily or frequent exposure or longer-term travelers with regular (e.g., a few times a month) exposure to environments that might harbor infected ticks. In addition, TBE vaccine may be considered for persons who might engage in outdoor activities in areas where ticks are likely to be found, with a decision to vaccinate made on the basis of an assessment of their planned activities and itinerary, risk factors for a poor medical outcome, and personal perception and tolerance of risk. In the laboratory setting, ACIP recommends TBE vaccine for laboratory workers with a potential for exposure to TBE virus

Tick-borne encephalitis in children

The incidence of tick-borne encephalitis in Norway is increasing. The risk of infection shows considerable geographical variations, with clusters of cases in certain municipalities in the counties of Agder, and Vestfold and Telemark. There is also a major variation in clinical presentation. Only a small number of cases of tick-borne encephalitis in children have been reported in Norway, and the condition may be underdiagnosed. We present a clinical review, including two case studies, that focuses on the clinical presentation and diagnosis of tick-borne encephalitis in children.

Effectiveness of Tick-borne Encephalitis Vaccines in Children, Latvia, 2018-2020

BACKGROUND

Tick-borne encephalitis (TBE) is an infection by the tick-borne encephalitis virus (TBEV) with symptoms of central nervous system inflammation. TBE is endemic in Latvia and other parts of Europe. TBE vaccination is recommended for children in Latvia. TBE vaccine effectiveness (VE) was estimated in Latvia, a country with high TBE incidence, providing the first VE estimates against a range of TBEV infection outcomes in children 1-15 years-of-age.

METHODS

Rīga Stradinš University conducted nationwide surveillance for suspected TBE cases. Serum and cerebrospinal fluid were ELISA tested for TBEV-specific IgG and IgM antibodies. A fully vaccinated child was an individual who had received the 3-dose primary series and appropriately timed boosters. The proportion of laboratory-confirmed TBE cases fully vaccinated (PCV) was determined from interviews and medical records. The proportion of the general population fully vaccinated (PPV) was determined from national surveys conducted in 2019 and 2020. TBE VE in children 1-15 years-of-age was estimated using the screening method: VE = 1 - [PCV/(1 - PCV)/PPV/(1 - PPV)].

RESULTS

From 2018 to 2020, surveillance identified 36 TBE cases in children 1-15 years-of-age; all were hospitalized, 5 (13.9%) for >12 days. Of the TBE cases, 94.4% (34/36) were unvaccinated compared with 43.8% of children in the general population. VE against TBE hospitalization in children 1-15 years-of-age was 94.9% (95% confidence interval 63.1-99.3). In 2018-2020, vaccination in children 1-15 years-of-age averted 39 hospitalized TBE cases.

CONCLUSION

Pediatric TBE vaccines were highly effective in preventing TBE in children. Increasing TBE vaccine uptake in children is essential to maximize the public health impact of TBE vaccination.

Associations of the cerebrospinal fluid lymphocyte population with a clinical presentation of tick-borne encephalitis

In tick-borne encephalitis (TBE), lymphocytes infiltrating central nervous system are indispensable for the infection control, but also potentially immunopathogenic. To clarify their roles, we have evaluated cerebrospinal fluid (CSF) count of the main lymphocyte populations (considered as a proxy of the brain parenchyma lymphocytic infiltrate) in TBE patients and analyzed if they associate with clinical presentation, blood-brain barrier disruption and intrathecal antibody synthesis. We have studied CSF from 96 adults with TBE (50 with meningitis, 40 with meningoencephalitis, 6 with meningoencephalomyelitis), 17 children and adolescents with TBE and 27 adults with non-TBE lymphocytic meningitis. Th CD3+CD4+, Tc CD3+CD8+, double positive T CD3+CD4+CD8+, B CD19+ and NK CD16+/56+ cells were counted cytometrically with a commercial fluorochrome-stained monoclonal antibody set. The associations between the counts and fractions of these cells and clinical parameters were analyzed with non-parametric tests, p<0.05 considered significant. The TBE patients had lower pleocytosis with similar proportions of the lymphocyte populations compared to non-TBE meningitis. The different lymphocyte populations correlated positively with one another, as well as with CSF albumin, IgG and IgM quotients. The higher pleocytosis and expansion of Th, Tc and B cells associated with a more severe disease and neurologic involvement: Th with encephalopathy, myelitis and weakly with cerebellar syndrome, Tc with myelitis and weakly with encephalopathy, B with myelitis and with at least moderately severe encephalopathy. The double-positive T lymphocytes associated with myelitis, but not with other forms of CNS involvement. The fraction of double positive T cells decreased in encephalopathy and the fraction of NK in patients with neurologic deficits. In children with TBE, Tc and B counts were increased at the expense of Th lymphocytes in comparison with adults. The concerted intrathecal immune response, involving the main lymphocyte populations, increases with the clinical severity of TBE, with no evidently protective or pathogenic elements distinguishable. However, the particular populations including B, Th and Tc cells associate with different, though overlapping, spectra of CNS manifestations, suggesting they may be specifically related to TBE manifesting as myelitis, encephalopathy and cerebellitis. The double-positive T and NK cells do not expand evidently with severity and may be most closely associated with the protective anti-TBEV response.

Tick-borne encephalitis: Acute clinical manifestations and severity in 581 cases from Germany, 2018-2020

OBJECTIVES

Tick-borne encephalitis (TBE) is a growing public health problem with an average of 361 cases notified annually to Germany's passive surveillance system since 2001. We aimed to assess clinical manifestations and identify covariates associated with severity.

METHODS

We included cases notified 2018-2020 in a prospective cohort study and collected data with telephone interviews, questionnaires to general practitioners, and hospital discharge summaries. Covariates' causal associations with severity were evaluated with multivariable logistic regression, adjusted for variables identified via directed acyclic graphs.

RESULTS

Of 1220 eligible cases, 581 (48%) participated. Of these, 97.1% were not (fully) vaccinated. TBE was severe in 20.3% of cases (children: 9.1%, ≥70-year-olds: 48.6%). Routine surveillance data underreported the proportion of cases with central nervous system involvement (56% vs. 84%). Ninety percent required hospitalization, 13.8% intensive care, and 33.4% rehabilitation. Severity was most notably associated with age (odds ratio (OR): 1.04, 95% confidence interval (CI): 1.02-1.05), hypertension (OR: 2.27, 95%CI: 1.37-3.75), and monophasic disease course (OR: 1.67, 95%CI: 1.08-2.58).

CONCLUSIONS

We observed substantial TBE burden and health service utilization, suggesting that awareness of TBE severity and vaccine preventability should be increased. Knowledge of severity-associated factors may help inform patients' decision to get vaccinated.

Tick-borne encephalitis in pediatrics: An often overlooked diagnosis

Tick-borne encephalitis (TBE) is a vector-borne disease caused by a flavivirus, the tick-borne encephalitis virus (TBEV), and transmitted by the bite of infected Ixodes ricinus ticks. The European subtype (TBEV-Eu) is endemic in 27 European countries. During the last decade, increased TBE incidence was observed in many countries, including some of those believed to be of low endemicity/devoid of TBEV circulation. However, data dealing with TBE in children are far less profuse than with adults. Historically, children are known to have mild TBEV infection with favorable outcomes. That said, recent case reports and observational studies on pediatric cohorts have challenged this point of view. Like adults, children may present severe forms and fail to completely recover following TBE infection, at times leading to long-term cognitive impairment. In this review, we comprehensively describe the incidence, exposure factors, and transmission routes of TBEV in children, as well as the clinical and biological manifestations of TBE and imaging findings in this population. We also harness new data on long-term outcomes and sequelae in pediatric cohorts. Finally, we provide an overview of vaccination recommendations for children in European countries.

Vaccine uptake in 20 countries in Europe 2020: Focus on tick-borne encephalitis (TBE)

Vaccination as a highly effective measure to protect against tick-borne encephalitis (TBE) comes into new focus as known risk areas are expanding across Europe and Asia. Here we present an online household survey conducted in 20 European countries spanning endemic and non-endemic regions of TBE in 2020. With a comprehensive and standardized list of questions, this survey provided a unique opportunity to compare TBE/TBE vaccine awareness, TBE severity perception, vaccine uptake, vaccination completeness/compliance and motivators/barriers for vaccination across Europe. Among the 51,478 participants, tetanus- (72-92%), influenza- (83-98%), and measles-awareness (79-96%) were highest, but awareness was low for Lyme borreliosis, bacterial meningitis and pneumococcal pneumonia. Awareness towards TBE and a TBE vaccine was 74% and 56% in endemic countries, respectively, compared to 30% and 12% in non-endemic countries. Vaccine uptake defined as at least one TBE vaccination was found to be highly heterogenous across both endemic (range 7-81%) and non-endemic countries (range 1-8%). Compliance with the recommended vaccination schedule was 21% for the primary vaccination series and dropped to 7% for the first booster vaccination in endemic countries. The percentage of participants protected against TBE by vaccination at the time of the survey ranged from 21% in Slovakia to 69% in Lithuania. The perception of personal risk or lack thereof was found to be the most influencing factor for and against TBE vaccination. Overall, these data indicate highly heterogenous responses in different European countries regarding not only awareness towards a TBE vaccine, but also regarding TBE vaccine uptake and compliance. Regionally focused strategies to increase diagnostic completeness as well as TBE vaccination are needed across Europe.

A Retrospective Analysis of Tick-borne Encephalitis in Children Treated in Kaunas Hospital During 2012 to 2019

BACKGROUND

Lithuania has the highest tick-borne encephalitis (TBE) rates in Europe. Although TBE incidence in children is lower, it may still cause long-term consequences. So far pediatric epidemiological and clinical characteristics of TBE in Lithuania were not described.

METHODS

We performed a retrospective analysis of 87 cases of children who were hospitalized for TBE in Kaunas Hospital of the Lithuanian University of Health Sciences from 2012 to 2019. Each case was identified with neurological symptoms and positive serological tests.

RESULTS

Around half of the children (50.6%) reported having a tick bite, whereas 6.9% stated having exposure to unpasteurized milk. Biphasic course of the disease occurred in 70.1% of the cases. The most common clinical symptoms were headache (100%), fever (100%), nausea (85.1%), vomiting (78.2%), drowsiness (67.8%) and general weakness (66.7%). Meningeal symptoms were present in 93.1% of the cases, and 93.1% of the children had at least one focal neurological sign (tremor 82.3%, impaired balance 73.6%). Isolated meningitis was diagnosed in 57.5%, meningoencephalitis in 41.4% and meningoencephalomyelitis in 1.1% of the cases. Majority of younger children (1-8 years old) had meningitis (77.3%), whereas 49.2% of older children (9-17 years old) had more severe forms of TBE. Cerebrospinal fluid pleocytosis was found in 94.3% of cases (average white blood cell count: 111.7 per μL, protein: 0.5 g/L). Higher levels of cerebrospinal fluid protein were associated with more severe forms of TBE and older age. Duration of the symptomatic disease lasted ≈11 days. Early residual signs were observed in 75.9% of all cases.

CONCLUSIONS

The epidemiological and clinical characteristics of TBE in children in Lithuania are similar to those described in other countries. Only half of the subjects reported having a tick bite. Younger children tend to suffer from meningoencephalitis and meningoencephalomyelitis less frequently than elder ones. Focal neurological signs were commonly observed. Majority of children had lasting symptoms of TBE upon discharge from the hospital.

Back to School: Academic Functioning and Educational Needs among Youth with Acquired Brain Injury

Youth with a history of traumatic or non-traumatic acquired brain injury are at increased risk for long-lasting cognitive, emotional, behavioral, social, and physical sequelae post-injury. Such sequelae have great potential to negatively impact this population’s academic functioning. Consistently, poorer academic achievement and elevated need for educational supports have been well-documented among youth with a history of acquired brain injury. The current paper reviews the literature on neuropsychological, psychiatric, and academic outcomes of pediatric acquired brain injury. A discussion of special education law as it applies to this patient population, ongoing limitations within the field, and a proposal of solutions are also included.

Photophobia in headache disorders: characteristics and potential mechanisms

Photophobia is present in multiple types of headache disorders. The coexistence of photophobia and headache suggested the potential reciprocal interactions between visual and pain pathways. In this review, we summarized the photophobic characteristics in different types of headache disorders in the context of the three diagnostic categories of headache disorders: (1) primary headaches: migraine, tension-type headache, and trigeminal autonomic cephalalgias; (2) secondary headaches: headaches attributed to traumatic brain injury, meningitis, non-traumatic subarachnoid hemorrhage and disorder of the eyes; (3) painful cranial neuropathies: trigeminal neuralgia and painful optic neuritis. We then discussed potential mechanisms for the coexistence of photophobia and headache. In conclusion, the characteristics of photophobia are different among these headache disorders. The coexistence of photophobia and headache is associated with the interactions between visual and pain pathway at retina, midbrain, thalamus, hypothalamus and visual cortex. The communication between these pathways may depend on calcitonin gene-related peptide and pituitary cyclase-activating polypeptide transmission. Moreover, cortical spreading depression, an upstream trigger of headache, also plays an important role in photophobia by increased nociceptive input to the thalamus.

The Unexpected Holiday Souvenir: The Public Health Risk to UK Travellers from Ticks Acquired Overseas

Overseas travel to regions where ticks are found can increase travellers' exposure to ticks and pathogens that may be unfamiliar to medical professionals in their home countries. Previous studies have detailed non-native tick species removed from recently returned travellers, occasionally leading to travel-associated human cases of exotic tick-borne disease. There are 20 species of tick endemic to the UK, yet UK travellers can be exposed to many other non-native species whilst overseas. Here, we report ticks received by Public Health England's Tick Surveillance Scheme from humans with recent travel history between January 2006 and December 2018. Altogether, 16 tick species were received from people who had recently travelled overseas. Confirmed imports (acquired outside of the UK) were received from people who recently travelled to 22 countries. Possible imports (acquired abroad or within the UK) were received from people who had recently travelled to eight European countries. Species-specific literature reviews highlighted nine of the sixteen tick species are known to vector at least one tick-borne pathogen to humans in the country of acquisition, suggesting travellers exposed to ticks may be at risk of being bitten by a species that is a known vector, with implications for novel tick-borne disease transmission to travellers.

Comparison of tick-borne encephalitis between children and adults-analysis of 669 patients

The aim of our study was to compare the course of TBE in children and adults. A retrospective analysis of the medical records of 669 patients was performed. The patients were categorized into 2 groups: Group I with 68 children and group II with 601 adults. TBE symptoms in children were milder compared with adults, with meningitis in 97% of cases. In adults, meningoencephalitis and meningoencephalomyelitis made up 49.26% of cases. Nausea and vomiting are more frequent in children, while neurological manifestations are more frequent in adults. There were no differences in CSF pleocytosis at the onset of disease in both groups, while CSF protein concentration was higher in adults. Children treated with corticosteroids over 7 days had higher checkup pleocytosis than pleocytosis at the onset of disease compared with adults. Corticosteroid use prolongs the disease duration but does not influence the development of TBE sequelae. Children had more favourable outcomes than adult patients.

Tick-borne encephalitis virus (TBEV) infection in pregnancy: Absence of virus transmission to the fetuses despite severe maternal disease - A case study

Tick-borne encephalitis (TBE) is an emerging infectious disease in large parts of Europe and Asia. Whereas other members of the Flaviviridae family can harm fetal development, there are only very few reports on TBE virus (TBEV) infections during pregnancy. Thus, the implications for fetal health remain largely unknown. In this study, we present detailed pre- and postnatal health assessment of three children in the context of severe maternal TBEV infection during pregnancy. Following acute TBEV infection of the mothers, intrauterine growth and development of all children were assessed by repetitive prenatal ultrasound. Postnatal examinations included clinical and virological analyses over a follow-up period of 18 months. Prenatally, no signs of intrauterine growth restrictions were observed. All neonates were delivered at term. Umbilical cord blood of the newborns tested negative for TBEV RNA. Virus-specific IgG antibodies were positive at birth but negative at 9 and 11 months of age. Importantly, IgM antibodies remained negative throughout the period of observation. Taken together, these clinical and virological data strongly suggest that fetal TBEV infection did not occur, despite severe manifestations in the mothers.

The lymphocyte populations and their migration into the central nervous system in tick-borne encephalitis

In tick-borne encephalitis (TBE) the cerebrospinal fluid (CSF) cytosis is dominated by T CD3+CD4+ and T CD3+CD8+ lymphocytes, but their pathogenetic roles and mechanisms of migration into central nervous system (CNS) are unclear. Currently, we have studied CSF lymphocyte subsets and chemotactic axes in TBE patients stratified according to the clinical presentation. Blood and CSF were obtained from 51 patients with TBE (presenting as meningitis in 30, meningoencephalitis in 18 and meningoencephalomyelitis in 3), 20 with non-TBE meningitis and 11 healthy controls. We have studied: (1) abundances of the main lymphocyte subsets and (2) CXCR3 and CCR5 expression on CD3+CD4+ and CD3+CD8+ lymphocytes cytometrically with fluorochrome-stained monoclonal antibodies; (3) concentrations of chemotactic cytokines: CCL5 (CCR5 ligand), CXCL10 (CXCR3 ligand), IL-16, CCL2, CCL20 and CXCL5 with ELISA. Cytokine concentrations were additionally studied in 8 pediatric TBE patients. Data were analyzed with non-parametric tests, p < 0.05 considered significant. The higher CSF lymphocyte counts were associated with symptoms of CNS involvement, especially with altered consciousness (B, Th and Tc cells) and focal neurologic deficits (B cells). The minor fraction of double-positive T CD4+CD8+ cells was unique in associating negatively with encephalitis and altered consciousness. CSF CD3+CD4+ and CD3+CD8+ lymphocyte population was enriched in CCR5-positive cells and CCL5 concentration in CSF was increased and associated with a milder presentation. Although CXCL10 was vividly up-regulated intrathecally and correlated with CSF T lymphocyte counts, the CXCR3 expression in CSF T lymphocytes was low. Serum and CSF concentrations of CCL2, CXCL5 and IL-16 were increased in adult TBE patients, CCL2 created a chemotactic gradient towards CSF and both CCL2 and IL-16 concentrations correlated positively with CSF lymphocyte counts. The particular lymphoid cell populations in CSF associate differently with the clinical presentation of TBE, suggesting their distinct roles in pathogenesis. CCR5/CCL5 axis probably contributes to T lymphocyte migration into CNS. CXCL10 mediates the intrathecal immune response, but is probably not directly responsible for T cell migration. Additional chemotactic factors must be involved, probably including CCL2 and IL-16.

Comparison of Neuroborreliosis Between Children and Adults

BACKGROUND

Lyme neuroborreliosis (NB) is a tick-borne infectious disorder of the nervous system caused by Borrelia burgdorferi spirochetes. There are not many data available regarding the differences in the course of NB in children and adults. The aim of our study was to compare the clinical course of NB between children and adults.

METHODS

Retrospective analysis of medical documentation of 181 patients with NB was performed. The patients were divided into 2 groups: Group I: 57 children with NB; Group II: 124 adults with NB. Medical data, such as patients' age, sex, place of living (residence), time from a tick bite, subjective complaints, general examination results, laboratory parameters and treatment were analyzed.

RESULTS

In children, the most common symptoms were headache (89.5%), neck stiffness (64.9%) and nausea and vomiting (56.1%). In adults, the most common symptoms were headache (77.4%), facial nerve palsy (59.7%), neck stiffness (59.7%), vertigo (41.9%) and lumbosacral region pain (37.1%). Bannwarth's syndrome was observed in 10.5% of children and 36.3% of adults. In cerebrospinal fluid (CSF) in children, the pleocytosis at admission was higher than in adults, but protein concentration was significantly lower. There were no differences in percentage of mononuclear cells in CSF smear between the groups. In CSF examination after treatment, a decrease in pleocytosis and protein concentration was observed in both groups. Analysis of effectiveness of treatment mostly with third generation cephalosporins (defined as complete recovery) between the groups, calculated by the Kaplan-Meier method and compared with the use of the log-rank test, showed no significant differences between children and adults (log-rank P = 0.619).

CONCLUSIONS

In children, NB more frequently presented as meningitis, and in adults in the form of Bannwarth's syndrome. CSF pleocytosis in children with NB was higher than in adults, while the protein concentration in children was lower. Outcomes in children and adults were favorable and did not differ after standard NB treatment.

Virus RNA Load in Patients with Tick-Borne Encephalitis, Slovenia

We determined levels of tick-borne encephalitis (TBE) virus (TBEV) RNA in serum samples obtained from 80 patients during the initial phase of TBE in Slovenia. For most samples, levels were within the range of 3-6 log₁₀ copies RNA/mL. Levels were higher in female patients than in male patients, but we found no association between virus load and several laboratory and clinical parameters, including severity of TBE. However, a weak humoral immune response was associated with a more severe disease course, suggesting that inefficient clearance of virus results in a more serious illness. To determine whether a certain genetic lineage of TBEV had a higher virulence potential, we obtained 56 partial envelope protein gene sequences by directly sequencing reverse transcription PCR products from clinical samples of patients. This method provided a large set of patient-derived TBEV sequences. We observed no association between phylogenetic clades and virus load or disease severity.

Reviewing estimates of the burden in disability-adjusted life years (DALYs) of tick-borne encephalitis in Slovenia

INTRODUCTION

Tick-borne encephalitis (TBE) reflects an increasing burden and can affect public health policy. Vaccination could be the most effective option to reduce the disease burden, this review can support national recommendations for TBE vaccination in Slovenia.

AREAS COVERED

This burden is relatively high in Slovenia and can be estimated by using an incidence-based disability-adjusted life years (DALYs) methodology. Notably, DALYs have been estimated for Slovenia in various studies. The present study summarizes the main differences and conclusions between two studies that dealt with the calculation of DALYs for TBE in Slovenia. The databases of PubMed and Embase were used to get information about publications that dealt with the TBE burden, using an incidence-based DALYs methodology, in Slovenia.

EXPERT OPINION

Permanent sequelae contribute the most to the total burden in DALYs. Increasing vaccination in all ages and age groups can be the most effective and efficient strategy to reduce the burden of TBE and protect the whole population health.

Factors associated with severity of tick-borne encephalitis: A prospective observational study

BACKGROUND

Information on parameters associated with the severity of tick-borne encephalitis (TBE) is limited.

METHODS

The association between 15 pre-defined parameters and the severity of TBE was evaluated in 717 consecutive adult patients diagnosed in Slovenia 2007-2012.

RESULTS

Multivariable logistic regression showed that patient age (odds ratio, OR 1.26, 95% CI 1.11-1.44; P = 0.001), previous vaccination against TBE (OR 14.23, 95% CI 1.72-117.87; P = 0.014), blood leukocyte count (OR 1.45, 95% CI 1.13-1.85; P = 0.004), and level of specific TBE virus serum IgG antibodies (OR 0.85, 95% CI 0.75-0.96; P = 0.009) were associated with severe acute illness based on the clinical diagnosis. When severity of TBE was based on the severity score and linear regression was used, corresponding association was found for age (estimated coefficient, EC 1.70, 95% CI 1.06-2.33; P<0.001), previous vaccination against TBE (EC 11.16, 95% CI 5.05-17.27; P < 0.001), serum C-reactive protein level (EC 1.20, 95% CI 0.48-1.91; P = 0.001), and level of specific TBE virus serum IgG antibodies (EC -0.74, 95% CI -1.27-0.20; P = 0.007).

CONCLUSIONS

Previous vaccination against TBE, low levels of TBE virus serum IgG antibodies, older age, higher blood leukocyte count, and higher serum C-reactive protein levels are associated with more severe TBE.

Fatigue following Paediatric Acquired Brain Injury and its Impact on Functional Outcomes: A Systematic Review

Fatigue is a commonly reported sequela following an acquired brain injury (ABI), and can have a negative impact on many areas of a child's life. However, there is minimal research that focuses on fatigue specifically, and so factors such as its occurrence, duration, and impact on functioning remain uncertain. This systematic review aims to provide a comprehensive summary of the research to date, bringing together a number of studies with a focus on paediatric ABI and fatigue. Terms were searched in relevant databases (PsycInfo, Medline, CINAHL), and articles were included or excluded based on specified criteria. Of the 1177 papers identified in the original search, a total of 9 papers met inclusion criteria, and were categorised as traumatic brain injury (TBI; n = 4), meningitis and meningococcal disease (n = 2), brain tumours (n = 2), and mixed ABI group (n = 1). Key findings suggest that fatigue is a problem encountered by a significant proportion of patients in all the studies reviewed, and often occurred regardless of the cause; fatigue was also associated with poor academic achievement, limited physical activity, and social and emotional problems. Injuries of greater severity were associated with higher levels of fatigue and worse outcomes. Several management options were suggested, though their efficacy was not reported. Future research is required with a suggested focus on using multiple time points to better understand the trajectories of fatigue following childhood ABI, and to build an evidence base to determine which management options are most suitable.

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.

Increased working memory related fMRI signal in children following Tick Borne Encephalitis

OBJECTIVE

Tick Borne Encephalitis (TBE) is a viral infection in the central nervous system endemic in Europe and Asia. While pediatric infection may carry a lower risk for serious neurological sequelae compared to adults, a large proportion of children experience long term cognitive problems, most markedly decreased working memory capacity. We explored whether task related functional magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) could reveal a biological correlate of status-post TBE in children.

METHODS

We examined 11 serologically verified pediatric TBE patients with central nervous system involvement with 55 healthy controls with working memory tests and MRI.

RESULTS

The TBE patients showed a prominent deficit in working memory capacity and an increased task related functional MRI signal in working memory related cortical areas during a spatial working memory task performed without sedation. No diffusion differences could be found with DTI, in line with the reported paucity of anatomical abnormalities.

CONCLUSION

This study is the first to demonstrate functional MRI abnormalities in TBE patients that bears similarity to other patient groups with diffuse neuronal damage.

The Burden of Tick-Borne Encephalitis in Disability-Adjusted Life Years (DALYs) for Slovenia

BACKGROUND

Tick-borne encephalitis (TBE) presents an increasing burden in many parts of Europe, Asian Russia, Siberia, Asian former USSR and Far East. Incidence can be considered as one way to express the burden. A more comprehensive measure concerns disability-adjusted life years (DALYs), better characterizing the full burden of TBE. TBE burden in DALYs has not yet been estimated, nor has it been specified by the Global Burden of Disease (GBD) studies.

OBJECTIVE

The purpose of the present study is to estimate the burden of TBE in Slovenia, expressed in DALYs, both from the population and individual perspectives. We discuss the impact of TBE burden on public health and potential strategies to reduce this burden in Slovenia.

METHODS

The burden of TBE is estimated by using the updated DALYs' methodology first introduced in the GBD project. The DALYs᾽ calculations are based on the health outcomes of the natural course of the disease being modelled. Corrections for under-reporting and under-ascertainment are applied. The impact of uncertainty in parameters in the model was assessed using sensitivity analyses.

RESULTS

From the population perspective, total DALYs amount to 3,450 (167.8 per 100,000 population), while from the individual perspective they amount to 3.1 per case in 2011. Notably, the consequences of TBE present a larger burden than TBE itself.

CONCLUSIONS

TBE presents a relatively high burden expressed in DALYs compared with estimates for other infectious diseases from the GBD 2010 study for Slovenia. Raising awareness and increasing vaccination coverage are needed to reduce TBE and its consequences.

Tick-borne encephalitis: A review of epidemiology, clinical characteristics, and management

Tick-borne encephalitis is an infection of central nervous system caused by tick-borne encephalitis virus transmitted to humans predominantly by tick bites. During the last few decades the incidence of the disease has been increasing and poses a growing health problem in almost all endemic European and Asian countries. Most cases occur during the highest period of tick activity, in Central Europe mainly from April to November. Tick-borne encephalitis is more common in adults than in children. Clinical spectrum of the disease ranges from mild meningitis to severe meningoencephalitis with or without paralysis. Rare clinical manifestations are an abortive form of the disease and a chronic progressive form. A post-encephalitic syndrome, causing long-lasting morbidity that often affects the quality of life develops in up to 50% of patients after acute tick-borne encephalitis. Clinical course and outcome vary by subtype of tick-borne encephalitis virus (the disease caused by the European subtype has milder course and better outcome than the disease caused by Siberian and Far-Easter subtypes), age of patients (increasing age is associated with less favorable outcome), and host genetic factors. Since clinical features and laboratory results of blood and cerebrospinal fluid are nonspecific, the diagnosis must be confirmed by microbiologic findings. The routine laboratory confirmation of the tick-borne encephalitis virus infection is based mainly on the detection of specific IgM and IgG antibodies in serum (and cerebrospinal fluid), usually by enzyme-linked immunosorbent assay. There is no specific antiviral treatment for tick-borne encephalitis. Vaccination can effectively prevent the disease and is indicated for persons living in or visiting tick-borne encephalitis endemic areas.

Clinical course and sequelae for tick-borne encephalitis among children in South Moravia (Czech Republic)

This study of 170 children in the Czech Republic examines the clinical course and sequelae for tick-borne encephalitis. Evaluated were demographic and epidemiological data, signs and symptoms at admission, clinical course during hospital stay and laboratory findings. Cerebrospinal fluid was analysed for white blood cells, protein, impairment of blood-cerebrospinal fluid (CSF) barrier and tick-borne encephalitis virus (TBEV)-specific antibodies. Subjective complaints and objective neurological deficits were investigated. Tick bites were reported in 74 % of the children. The illness had a biphasic clinical course in 58 % of cases. The second phase was characterized by headache in 98 %, high fever in 86 % (more than 38.5 °C), vomiting in 64 % and meningeal signs in 92 % of children. Meningitis (77 %) dominated over meningoencephalitis (13 %). Inflammatory changes in CSF were found in 90 % of children. Immunoglobulin M (IgM) antibodies against TBEV in serum were found early in the infection in 99 %. IgM positivity lasted up to 1,126 days. Neurocognitive abnormalities were found in 19 (11 %) of children. Acquired aphasia, lasting tremor of the upper extremities, speech impairment, inversion of sleep and wakefulness, abnormal hyperkinetic movements and vertigo were found to be permanent but not progressing. Severe sequelae persisted in two children (1 %) while in three (2 %) were classified as mild or moderate.

CONCLUSION

Tick-borne encephalitis in children has a benign course with minimal sequelae. Meningitis with biphasic course is the prevalent involvement and the duration of IgM antibodies in serum and index of positivity are not decisive for postencephalitic disorders.

Quantitative evaluation of the severity of acute illness in adult patients with tick-borne encephalitis

The aim of the present study was to quantify the severity of acute illness in patients with tick-borne encephalitis and to ascertain this approach by comparing it to standard clinical assessment. We designed scoring system for quantification of the severity of acute illness in patients with tick-borne encephalitis. Certain number of points was allotted to the presence, intensity, and duration of individual symptoms/signs. According to the obtained score the disease was classified as mild, moderate, and severe. Tick-borne encephalitis was assessed clinically as mild when only signs/symptoms of meningeal involvement were found, moderate in case of monofocal neurological signs and/or mild to moderate signs/symptoms of central nervous system dysfunction, and severe in patients with multifocal neurological signs and/or symptoms of severe dysfunction of central nervous system. By designed scoring system 282 adult patients, 146 males and 136 females, average aged 52.2 ± 15.5 years (range 15–82 years), with confirmed tick-borne encephalitis, were prospectively assessed. In 279/282 (98.9%) patients the severity according to clinical assessment matched with the score ranges for mild, moderate, and severe disease. The proposed approach enables precise and straightforward appraisal of the severity of acute illness and could be useful for comparison of findings within/between study groups.

Tick-borne encephalitis carries a high risk of incomplete recovery in children

OBJECTIVE

To examine long-term outcome after tick-borne encephalitis (TBE) in children.

STUDY DESIGN

In this population-based cohort, 55 children with TBE with central nervous system involvement infected during 2004-2008 were evaluated 2-7 years later using the Rivermead post-concussion symptoms questionnaire (n = 42) and the Behavior Rating Inventory of Executive Functioning for parents and teachers (n = 32, n = 22, respectively). General cognitive ability was investigated in a subgroup (n = 20) using the Wechsler Intelligence Scale for Children, 4th edition.

RESULTS

At long-term follow-up, two-thirds of the children experienced residual problems, the main complaints being cognitive problems, headache, fatigue, and irritability. More than one-third of the children were reported by parents or teachers to have problems with executive functioning on the Behavior Rating Inventory of Executive Functioning, mainly in areas involving initiating and organizing activities and working memory. Children who underwent Wechsler Intelligence Scale for Children, 4th edition testing had a significantly lower working memory index compared with reference norms.

CONCLUSION

A large proportion of children experience an incomplete recovery after TBE with central nervous system involvement. Cognitive problems in areas of executive function and working memory are the most prevalent. Even if mortality and severe sequelae are low in children after TBE, all children should be followed after TBE to detect cognitive deficits.

Tick-borne encephalitis in children and adolescents in the Czech Republic between 1960 and 2007

BACKGROUND

The Czech Republic ranks among the countries with the highest prevalence of tick-borne encephalitis worldwide. The region of West Bohemia has the second highest morbidity within the Czech Republic.

METHODS

Between 1960 and 2007, laboratories confirmed 410 cases of tick-borne encephalitis in children and adolescents of West Bohemia. Available epidemiological data were analyzed.

RESULTS

The highest incidence (per 100 000 population) was found in the group of 15-19 years for both genders (males: 6.2; females: 4.3). Data on the consumption of non-pasteurized milk were found in 5.4% of patients. The preschool age group showed its highest incidence in June and September, and the risk of infection for older children was in July and August.

CONCLUSIONS

The current low coverage of vaccination leads to an insignificant improvement to the overall frequency of this disease.

One-year follow-up of tick-borne central nervous system infections in childhood

BACKGROUND

Neurologic sequelae, including cognitive deficits, after childhood tick-borne encephalitis (TBE) and neuroborreliosis (NB) are not well-characterized. These infections are among the most common affecting the central nervous system in children and can be difficult to diagnose due to vague symptomatology. The aim of this study was to investigate long-term (>1 year) consequences of pediatric TBE and NB as well as the value of markers for brain damage and genetic susceptibility.

METHODS

From a previous prospective study, children diagnosed with TBE (n = 8) and NB (n = 12) as well as pediatric controls (n = 15) were followed up by clinical examination, semistructured interview and screening for cognitive dysfunction by the Five-to-Fifteen Questionnaire. The follow-up also included detection of serum autoantibodies against the neural proteins; glial fibrillary acidic protein and myelin basic protein, as well as genotyping of a 32 basepair deletion in the chemokine receptor type 5 gene.

RESULTS

Children diagnosed with TBE displayed significantly more long-term subjective complaints (ie, fatigue, headache and irritability) compared with the NB and control groups. Significantly higher frequency of disabilities was also detected by the Five-to-Fifteen Questionnaire in the TBE group. Both TBE and NB cause consequences (eg, prolonged convalescence, worries and financial loss) for the families. Markers for genetic susceptibility and brain damage had no prognostic values in this cohort.

CONCLUSIONS

Pediatric TBE results in long-lasting residual symptoms and neurologic deficits affecting daily life. Vigilance for TBE-related morbidity among pediatricians and long-term clinical follow-up with assessment of cognitive dysfunctions and appropriate interventions seems reasonable for these children.

Antibody persistence after two vaccinations with either FSME-IMMUN® Junior or ENCEPUR® Children followed by third vaccination with FSME-IMMUN® Junior

Tick-borne encephalitis (TBE) vaccination strategies to induce optimal seroprotection in children are under constant evaluation. This multi-center, randomized, controlled, phase III clinical study examined antibody persistence in children aged 1-11 y following two prospectively administered doses of either the FSME-IMMUN® Junior or Encepur Children® vaccines, as well as investigating the immunogenicity, safety and vaccine interchangeability of a third vaccination with FSME-IMMUN(®) Junior. A high level of antibody persistence was observed in all subjects 6 mo after the first of two vaccinations with either pediatric TBE vaccine. Based on both immunological tests and viral antigens used, slightly higher seropositivity rates and higher GMCs /GMTs were found in children vaccinated with FSME-IMMUN® Junior compared with those who received Encepur® Children. Seropositivity rates across all age strata combined six months after the first vaccination with FSME-IMMUN® 0.25 mL Junior were 95.1% as determined by Immunozym ELISA, 93.2% as determined by Enzygnost ELISA and 95.3% as determined by NT; compared with 62.6%, 80.5% and 91.0% respectively after vaccination with Encepur® Children. A third vaccination with FSME-IMMUN(®) Junior induced 100% seropositivity in both study groups and was well tolerated as demonstrated by the low rates of systemic and injection site reactions. Subjects who received either FSME-IMMUN Junior® or Encepur(®) Children vaccine for the first two vaccinations and FSME-IMMUN Junior® for the third showed a comparably strong immune response regardless of the previous TBE vaccine administered, demonstrating that two vaccinations with Encepur® Children can successfully be followed by a third vaccination with FSME-IMMUN Junior®.

Pediatric tick-borne infections of the central nervous system in an endemic region of Sweden: a prospective evaluation of clinical manifestations

Tick-borne encephalitis (TBE) and neuroborreliosis (NB) are well-known central nervous system (CNS) infections in children. Childhood tick-borne CNS infections are generally described as mild conditions. However, this view has recently been challenged, and the natural course, including potential sequelae, has been debated. If the diseases present with nonspecific symptoms and signs, some children may elude diagnosis. This study estimates the incidence of symptomatic tick-borne CNS infections in children under medical care and describes the spectrum of manifestations. One hundred twenty-four children with neurologic symptoms attending the Pediatric Emergency Department were included prospectively. Anti-TBE virus and anti-Borrelia serology results were analyzed together with inflammatory parameters in the blood and cerebrospinal fluid. Nearly one fourth of the children with neurologic symptoms were diagnosed with a tick-borne CNS infection (TBE, n = 10 [8%] and NB, n = 21 [16.8%]). In general, these children displayed an indistinct medical history and presented with nonspecific signs such as malaise/fatigue and headache. Diagnosis was based on analysis of acute and convalescent sera. Blood inflammatory parameters were nonspecific and did not contribute to the diagnostics.

CONCLUSION

Pediatric tick-borne CNS infections are unexpectedly common and should be considered in children with unspecific and unexplained acute CNS-related symptoms.

High burden of tick-borne encephalitis in Slovenia--challenge for vaccination policy

Slovenia is one of the countries with the highest reported incidence rates of tick-borne encephalitis (TBE). Vaccination uptake is low, estimated to be 12.4%. TBE surveillance data for the last 20 years were analysed. Though nearly all of Slovenia is endemic for TBE with national yearly incidence rates up to 26.7/100,000, we showed that two regions (Gorenjska and Koroška) were much more affected than other seven regions, with annual incidence rates up to 57.2/100,000 and 76.9/100,000 population, respectively. In the last decade, there was a shift in the age distribution of reported TBE cases to the older age groups, which resulted in the highest age-specific incidence rates nationally in 55-64 age group (up to 33.4/100,000 in 2006). To reduce this high burden of TBE, ideally the whole population of Slovenia should be offered free of charge vaccination against TBE. Alternatively, in view of limited resources available, sensible approach would be increasing vaccination coverage of the general population using social marketing and increasing TBE awareness, and in addition, offering free of charge vaccination to the most affected groups. The following priority target groups should be considered to be prospectively covered with free of charge vaccination: (1) 45-69 years old individuals in the two most affected regions (Gorenjska, Koroška), (2) the remaining age groups in the two most affected regions, (3) 45-69 years old individuals in the region with the next highest TBE incidence rates (Ljubljana), and (4) individuals 45-69 years old in all remaining Slovenian regions.

Tick-borne encephalitis in childhood: rare or missed?

Retrospective evaluation of medical history and 3635 anti-TBE (tick-borne encephalitis) serologies during the years 2003-2008 indicates that childhood TBE is characterized by vague symptoms. Clinical findings suggest a nonspecific inflammatory disease with restricted encephalitic profile compared with adult TBE. Childhood TBE might elude diagnosis, which is unsatisfactory because of potential long-term consequences.

Clinical evaluation to determine the appropriate paediatric formulation of a tick-borne encephalitis vaccine

Two dose-finding studies and one open label safety study with a paediatric FSME-IMMUN formulation were conducted in children and adolescents aged 1-15 years (N=3697). The 1.2 microg antigen dose was identified as the optimal dose, inducing high seroconversion rates following the primary vaccination series. Adolescents (aged 12-15 years) vaccinated with the optimal paediatric dose (1.2 microg) attained similarly high seroprotective rates to adults (aged 16-35 years) vaccinated with the 2.4 microg formulation of FSME-IMMUN. We concluded that the FSME-IMMUN paediatric vaccine formulation is safe and highly immunogenic, not only for children <12 years, but also for adolescents <16 years.

Tick-borne encephalitis in Swiss children 2000-2004: five-year nationwide surveillance of epidemiologic characteristics and clinical course

Tick-borne encephalitis occurred in 55 children, ranging from 6 weeks to 15 years old. Average annual incidence was 1.0 per 100,000 in all children, and 0.4 per 100,000 in children less than 6 years old. Moderate to severe residua were present in 5 patients (9%) at hospital discharge and in one 9-year-old patient (1.8%) at follow-up. Permanent residua occur in children approximately 10 times less often than in adults.

Tick-borne encephalitis in Styrian children from 1981 to 2005: a retrospective study and a review of the literature

BACKGROUND

Tick-borne encephalitis in children appears to be more benign than in adults and shows also a more favourable outcome. Only some authors report of sequelae like paralysis, paresis or seizures and behavioural abnormalities. The aim was to describe the clinical features of tick-borne encephalitis in children with special attention to sequelae and to review the literature.

METHODS

Retrospective review of all charts of children with serologically confirmed tick-borne encephalitis hospitalised in Styria between 1981 and 2005.

RESULTS

One hundred sixteen children were diagnosed with tick-borne encephalitis. Ninety-two children (79.3%) developed meningitis and 24 (20.7%) meningoencephalitis. Eleven patients with meningoencephalitis showed somnolence, 5 confusion, 5 tremors, 2 facial palsy, 1 ataxia, 1 epileptic seizure and 1 hemi paresis. Seven patients had to be admitted to the intensive care unit. Two children (1.7%) developed long time neurological sequelae: one epileptic seizure with requirement of antiepileptic therapy and one left-sided hemi paresis. One hundred twelve children had been not and 3 incompletely vaccinated against tick-borne encephalitis. Only one child had been fully vaccinated according to the Austrian vaccination schedule.

CONCLUSION

Our study provides further evidence that tick-borne encephalitis in children has a substantial morbidity and in single cases severe long-time neurological sequelae are observed.

Tick-borne encephalitis in Slovenia from 2000 to 2004: comparison of the course in adult and elderly patients

OBJECTIVE

To present epidemiological data and clinical characteristics of tick-borne encephalitis (TBE) in adult patients, and to compare findings in the subgroup over the age of 60 years with those aged 60 or under.

METHODS

The information for this retrospective study was obtained by review of medical documentation. All patients over 15 years of age hospitalized at the Department of Infectious Diseases, University Medical Center Ljubljana, Slovenia, between 2000 and 2004 with pleocytosis (cerebrospinal fluid leukocyte count >5 x 10(6) cells/l) and the presence of serum IgM antibodies against TBE virus qualified for inclusion in this report. Patients were divided into two groups according to their age (patients over the age of 60 were classified as seniors and those aged 60 or under as adults); the findings in the two groups were compared.

RESULTS

Of 448 patients with TBE, 318 were in the adult group and 130 in the senior group. Males predominated in both groups. A biphasic course of the illness was reported by 56% of patients. There were no significant differences in the majority of clinical parameters in the initial phase of TBE but several distinctions between adults and seniors were found in the second phase of the illness. Adults more often presented with fever, headache, stiff neck and photophobia, whereas seniors more frequently reported fatigue, altered consciousness and decreased muscle strength, these differences indicating a more classic course of TBE in the younger group and a somehow different and more severe acute disease in the older group. More severe acute disease and less favorable outcome in seniors was further corroborated by the occurrence of urine retention (18/318, 5.7% versus 27/130, 20.8%; P < 0.001), frequency of pareses (10/318, 3.1% versus 7/130, 5.4%; P = 0.002) and the need for antiedematous treatment (103/318, 32.4% versus 61/130, 46.9%; P = 0.005), as well as by the duration of treatment, duration of hospital stay and the death rate (0/318 versus 3/130, 2.3%; P = 0.024). Several distinctions were present also in laboratory findings, including higher cerebrospinal fluid leukocyte count in the adults than in the seniors (107 x 10(6) cells/l versus 47 x 10(6) cells/l; P < 0.001).

CONCLUSION

Direct comparison of the course and outcome of TBE revealed several distinctions between patients over 60 years of age and those aged 60 or under and corroborates previous assumptions that TBE is a more serious illness in the elderly population.

Severe tick-borne encephalitis in Slovenia in the years 2001–2005: Time for a mass vaccination campaign?

The aim of this retrospective study was to assess some clinical, epidemiological and laboratory parameters of severe tick-borne encephalitis in Slovenia in the last five years, to compare them with published data, and to estimate need for providing a policy of active immunization. Thirty-three adult patients with a severe course of the disease, admitted to the intensive care unit of the Department of Infectious Diseases, University Medical Centre Ljubljana, Slovenia during a five year period, participated. All the patients had specific serum IgM antibodies against tick-borne encephalitis virus at admissions and IgG antibodies were present in 29 out of 33 patients. Twenty-two patients were admitted because of severe consciousness disturbances, nine suffered from spinal nerve paralysis, in two patients cranial nerve paralysis was observed, and one suffered from generalized tonic-clonic seizures. Ten patients were mechanically ventilated and three died. Leukocytosis in peripheral veins was found in twenty-one patients and nine had a C-reactive protein serum concentration over 50 mg/l. Nineteen patients had a cerebrospinal fluid leukocyte count exceeding 100 x 10(6)/l and a cerebrospinal fluid protein concentration was over the cut-off value of 0.45 g/l in majority. The findings of the present study confirmed some previous reports about clinical, epidemiological and laboratory characteristics of patients with severe tick-borne encephalitis. We have found that tick-borne encephalitis in Slovenia has a relatively low fatality rate. However, the severe course with long-lasting sequelae of the disease justifies vaccination of a risk population in endemic areas.