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Chapter 12a: Epidemiology by country – overview

serocomplex, has already been detected in TBEV subtype and vector
ticks and livestock in Spain.
distribution
An investigation in Turkish blood donors in
Zonguldak in the Black Sea region has shown Three main TBEV subtypes have been
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one TBEV positive sample by NT (PRNT). described based on their main distribution
However, cross-reactions in commercial sero- pattern and sequence similarity: the European
logical tests as well as by PRNT cannot be virus (previously CEE virus, Central European
entirely ruled out. Recently IgM but no IgG encephalitis virus, TBEV-EU), the Far Eastern
antibodies to TBEV were detected by ELISA in virus (previously RSSE virus, TBEV-FE), and the
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five children in Turkey. This constellation is Siberian virus (previously west Siberian virus,
highly implausible and indicates a unspecific TBEV-Sib). In addition to the 3 primary TBEV
cross reaction as well. More data on TBE are subtypes, there is a fourth accepted subtype
required in order to confirm the existence of (TBEV-BKL Baikalian subtype with the
the TBEV in Turkey. prototype strain 886-84). Two additional
lineages have been identified as possible TBEV
In a serological study in Northern Greece subtypes, namely the “886-84 group, and the
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serum samples from 921 apparently healthy Himalayan subtype (TBEV-HIM) (details see
individuals were investigated for the presence chapter 11).
of TBEV antibodies. According to the authors
two percent of the general population was TBEV-FE prevails in the regions of far-east
found to have seropositivity in the test Russia, in China, Mongolia and in Japan. TBEV-
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system. However TBEV is not endemic in SIB prevails in eastern and western Siberia, in
Greece, and most probably the seropreva- the Ural and European part of Russian
lence of TBE antibodies in humans is due to territories. TBEV-EU is predominant in Eastern
cross-reactivity to GGEV. Nonetheless two European countries including Ukraine, and in
imported ΤΒΕ cases confirmed by neutraliza- central, western, and northern Europe. TBEV-
tion test were reported to TESSy-ECDC, one in BLK was found in East Siberia near Lake Baikal
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2014 and a second in 2016. and in Northern Mongolia, and TBEV-HIM was
recently isolated in wild rodent Marmota
Recent data definitely confirmed the presence himalayana in the Qinghai-Tibet Plateau in
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of TBEV in Northern Italy (see country China.
chapter). Older data show up 14 human TBE
cases and two virus isolations between 1975 The principal carrier (vector) as well as the
and 2004, but no further TBE case has been reservoir for the TBEV-EU subtype is the tick I.
reported ever since. However, a ricinus, whereas TBEV-FE and TBEV-SIB
seroprevalence study in hunters and wild boar subtypes are transmitted predominantly by I.
breeders in Turin Province and in particular in persulcatus. The ranges of the 2 tick species as
the Susa valley showed an about 5% well as the TBEV subtypes overlap in the
seroprevalence by ELISA and amongst low risk Eastern parts of Estonia, Latvia, Finland, and
individuals seroprevalence was below 2%. 19 the European parts of Russia.
However, all 3 TBEV subtypes are present in
Estonia and Latvia. 21,22 From the limited virus

isolates done in Ukraine so far, there is
evidence that all TBEV subtypes are present
23,24
on the Crimean peninsula too. The TBEV-
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SIB has been detected in Bosnia as well.

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