Page 117 - TBE_Book_V2_2019

Chapter 5: TBE in adults

fatigue, myalgia, anorexia, nausea, and
Figure 2: Pleocytosis in CSF vomiting. However, fever and headache are
the chief complaints of patients presenting to
health services. This initial phase lasts for 2–4
days (range 1–8 days). 41,42

Overall, approximately 30% of all infected
individuals remain free of clinical signs and
symptoms, and 30–50% of all symptomatic
TBE patients experience only the initial phase;
however, epidemiological data show wide
variability. An estimated 30% of patients with
TBE who have gone through the initial phase
will develop a second phase with CNS
involvement. The asymptomatic period
between the first and second phase of
symptoms lasts for 8 (1–20) days. 41,43 Abortive
disease is diagnosed if there is only an
initial phase. The second phase of the disease
may involve the CNS with symptoms of
meningitis, meningoencephalitis, meningo-
encephalomyelitis, encephaloradiculitis, or
even mixed forms. A biphasic course is
observed in 74–85% of TBE patients infected
42
with TBEV-EU. Up to 46% of patients
experiencing the second phase of TBE develop
Pleocytosis in CSF; Percentage of cells seen in long-term sequelae. Interestingly, Kaiser et al.
pleocytosis at the onset of symptoms, and follow– report that patients with encephalomyelitis
up (Zajkowska, unpublished data). often present with only 1 phase (i.e., absence
41
of prodromal phase). Infections with the
Dynamics of TBE – first phase and second TBEV-Sib and the Far Eastern subtype of TBEV
phase (TBEV-FE) are predominantly monophasic.
Only a small remainder shows a biphasic or
44
During the viremic phase, extra-neural tissues, even chronic pattern (8–21%). An abortive
including the reticuloendothelial system form of TBEV infection presenting exclusively
(spleen, liver, and bone marrow), are infected with febrile temperatures, without CNS
and release TBEV. Viremia lasts for several involvement, has been reported in some
45
40
days and facilitates the invasion of the CNS. European studies. This abortive pattern
The outcome at this stage depends on the seems to be a rare clinical manifestation,
initial immune response at the entry site and estimated to account for 1.8% of all TBEV
46
the subsequent peripheral immune response. infections in Europe. In Russia, however,
Impaired clearance of viremia, and these abortive forms represent up to 50% of
39
consequent entry of TBEV to the CNS, are the all clinical presentations of TBE. The exact
result of a limited humoral response in the ratio of abortive versus CNS forms of TBE still
25
early course of TBEV infection. Flu-like remains unknown and depends on a variety of
8
symptoms develop during the initial viremic pathogen-related and individual host factors.
phase of the illness, including fever, headache,

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