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Chapter 12a: Epidemiology by country – overview

TBEV-EU foci have been reported in South Again, as noted above, the epidemiology of
Korea, approximately 7000 km away from the TBE is a ‘moving target.’ Current changes
European range of TBEV-EU subtype include an increase in geographical distribu-
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circulation. TBEV strains related to the TBEV- tion of TBE-risk areas as well as an overall
EU subtype were isolated in rodents and increase of reported TBE cases (Table 2).
humans in eastern and western Siberia as well
as in the Ural territory. 23,26 In recent years new TBE foci have been
reported from altitudes up to 2100 meters
TBEV-FE foci has not only been reported in above sea level 29,30,31 new endemic zones in
Crimea, about 3000 km away from the known previously unaffected alpine regions in
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TBEV-FE circulation area. it was also detect- western Austria and in Switzerland were
ed in the Republic of Moldova between 2010 established, and a first report of TBEV being
and 2011. detected at locations in Norway up to more
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than 65.°N was published 2018. A
Geographical circulation of the TBEV subtypes, remarkable increase in annual disease
unusual TBEV subtype foci, and various carrier numbers over the last couple of years is seen
vectors are described in more detail in in Central European countries, i.e. Austria,
Chapters 3 and 13. Czech Republic, Germany, Sweden, Switzer-
land (see Table 3)

Trends in TBE epidemiology Clearly, the areas with TBEV endemicity as
well as the total number of reported TBE cases

A characteristic feature of TBE is that the have increased over the last several decades.
incidence of the disease in risk areas can vary Comparing the periods from 1976 to 1989 and
significantly from year to year. In addition to 1990 to 2009, the average increase in TBE
short-term fluctuations, there are also longer- infections among humans in central and
range undulations of incidence rates in western European countries was 317.8% in
intervals of >5 years, which have been Europe including Russia and it was 193.2% in
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analyzed in detail for Austria, the Czech Europe excluding Russia.
1
Republic, and Slovenia (see Figure 4). Except
for the strong overall upsurge of TBE cases in Various factors may explain these findings at
the Czech Republic and Slovenia starting least in part: social factors (socio-political
changes, changes in human behavior, and
around 1992 (but not in Austria, as a result of
leisure time activities), ecological (e.g., effects
vaccination, mentioned above), the long-range
incidence curves for 1990–2011 are remark- of climate changes on vectors), and/ or
ably similar for all 3 countries, suggesting that technological factors (advanced diagnostics,
the causes for the increase in cases are the increased medical awareness). Certainly,
reporting of TBE cases has improved
same but not yet identified.
substantially over the years, and TBE is now a
A similar fluctuation over time has been notifiable disease in the EU. Most likely,
recognized in Estonia, a country with one of however, TBE was, and still is, considerably
the highest overall incidences in Europe. underreported. In the end, all factors
Looking into more detail for the years 2005 till mentioned above may play an ‘interactive
2017 incidence is fluctuating between 6.2 and role’ to explain these observed changes in TBE
18.6, and comparing the different counties epidemiology.
mean incidence (2005-2017) varies between
5.2 and 52.8 (see Chapter 12b, Estonia). The following country reports in Chapter 12b
provide a current state-of-the-art survey

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