Page 197 - TBE_Book_V2_2019

Chapter 11

General epidemiology

of TBE

Gerhard Dobler and Sergey Tkachev

Key Points

• Tick-borne encephalitis virus (TBEV) exists in natural foci, which are areas where TBEV is
circulating among its vectors (ticks of different species and genera) and reservoir hosts
(usually rodents and small mammals).
• Based on phylogenetic studies, four TBEV subtypes (Far-Eastern, Siberian, European,
Baikalian) and two putative subtypes (Himalayan and “178-79” group) are known. Within
each subtype, some genetic lineages are described.
• The European subtype (TBEV-EU) (formerly known also as the “Western subtype”) of TBEV is
prevalent in Europe, but it was also isolated in Western and Eastern Siberia in Russia and
South Korea.
• The Far-Eastern subtype (TBEV-FE) was preferably found in the territory of the far-eastern part
of Eurasia, but some strains were isolated in other regions of Eurasia.

• The Siberian (TBEV-SIB) subtype is the most common and has been found in almost all TBEV
habitat areas.
• The Baikalian subtype is prevalent around Lake Baikal and was isolated several times from ticks
and rodents.
• In addition to the four TBEV subtypes, one single isolate of TBEV (178-79) and two genetic
sequences (Himalayan) supposed to be new TBEV subtypes were described in Eastern Siberia and
China.
• The data on TBEV seroprevalence in humans and animals can serve as an indication for the
presence or absence of TBEV in studied area.

In the early 1920s, reports surfaced an expedition was organized to detect the
concerning a severe form of brain disease in origin of this unusual disease. During this first
woodcutters, topographers, road construction Taiga expedition to identify the etiology of a
workers, and residents of newly founded newly occurring form of encephalitis, Zil’ber et
1
villages in the Taiga forest in the far eastern al. showed that the etiologic agent of this
region of the former Soviet Union. The disease seemed to be a filterable pathogen
severity of the disease was such that in 1937 that was transmitted by ticks of the genera

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