The epidemiology, clinical presentation, and predictors of severe Tick-borne encephalitis in Lithuania, a highly endemic country: A retrospective study of 1040 patients

Abstract

Introduction In recent decades, the incidence of Tick-borne encephalitis (TBE) has been increasing and posing a growing health problem because of the high costs to the healthcare system and society. The clinical manifestations are well studied but there is a lack of research analyzing the severity of the disease. Objective The aim of this study was to analyze the epidemiology and clinical presentation of severe TBE, to identify the predictors for a severe disease course, and also predictors for meningoencephalomyelitic and severe meningoencephalitic/encephalitic forms. Methods A retrospective study was conducted in the Center of Infectious Diseases and the Center of Neurology at Vilnius University Hospital Santaros Klinikos in the years 2005–2017 to describe the clinical and epidemiological features of TBE in adults. Results 1040 patients were included in the study. A total of 152/1040 (14.6%) patients had a severe course. The highest proportion of severe cases, reaching 41.2%, was reported in the 70–79 year-old age group. A total of 36/152 (23.7%) severe patients presented meningoencephalomyelitis. Myelitic patients were older, were frequently infected in their living areas, and usually reported a monophasic disease course compared with severe meningoencephalitic/encephalitic patients. Severe meningoencephalitic/encephalitic patients, compared with non-severe meningoencephalitic/encephalitic, were older, less often noticed the tick bite, and often had a monophasic course. The sequelae on discharge were observed in 810/1000 (81%) of patients. Conclusions The prognostic factors associated with a severe disease course and severe meningoencephalitic form are: older age, comorbidities, a monophasic course, a fever of 40˚C and above, CRP more than 30 mg/l, CSF protein more than 1 g/l, delayed immune response of TBEV IgG, pathological findings in CT. Age above 60 years, presence of CNS disease, bulbar syndrome, pleocytosis 500x106/l and above, and delayed immune response of TBEV IgG are predictors of the most severe myelitic form.

Clinical and Laboratory Characteristics and Outcome of Illness Caused by Tick-Borne Encephalitis Virus without Central Nervous System Involvement

“…The finding of chills is somewhat surprising because chills are not common in patients with viral infections and are more characteristic of diseases caused by bacteria. Illness duration in our patients (median 7 days) was somewhat longer than reported in the literature (median 4–6, range 1–19 days) ( 5 , 6 , 8 , 9 , 12 , 26 , 32 , 34 ). In addition, in some patients, the illness was relatively severe: more than one third of patients were hospitalized.…”

Comparison of Clinical, Laboratory and Immune Characteristics of the Monophasic and Biphasic Course of Tick-Borne Encephalitis

“…Nonetheless, some patients with TBE have no (obvious) initial phase of the disease and present directly with central nervous system involvement. According to the reports consisting of 80 or more cases of TBE (presumably) caused by the European TBEV subtype, such a monophasic course is present in 13–44% of patients [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. In the present study, 283/705 patients (40.1%) had a monophasic course of the disease, which is a rather high proportion.…”

“…One of the main aims of the present study was to analyze clinical and laboratory characteristics associated with the monophasic course of TBE. Some studies showed that patients with monophasic presentation of TBE have a more severe clinical course of the disease than those with biphasic course [ 23 , 25 , 29 , 32 ] while several others did not find such association. In addition, some reports on patients with severe TBE who needed intensive care management [ 33 , 34 ] show an unusually high proportion of those with monophasic course (15/31, 48.4% and 21/33, 63.6%, respectively) suggesting that a more severe course of TBE is associated with the monophasic course of the disease.…”

Activation of Early Proinflammatory Responses by TBEV NS1 Varies between the Strains of Various Subtypes

“…In general, viruses of the European subtype cause rather light clinical manifestations with a mortality rate of less than 2% and patients with the Siberian subtype have generally mild forms of disease, but chronic forms of disease have also been registered, whereas infections with the Far-Eastern subtype cause the most severe manifestations of TBE and the highest mortality [ 5 , 6 ]. Clinical manifestations of TBE are well characterized, but the systemic analysis of disease severity factors are limited [ 7 , 8 , 9 , 10 ]. Therefore, an estimation of the factors defining the severity of TBE is vital.…”