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Chapter 12b: TBE in South Korea

(8.8%, 1,149/13,053), I. niponensis (0.3%, Overview of TBE in South Korea
42/13,053), and Ixodes persulcatus (0.05%,
6/13,053). The minimum field detection rate In South Korea, TBE is designated as a group 4
for H. longicornis, H. flava, and I. nipponensis Nationally Notifiable Infectious Disease,
was 0.06%, 0.17%, and 2.38%, respectively, requiring immediate reporting for laboratory-
8
and the TBEV sequences obtained were confirmed cases.
identified as the Western subtype, consistent
with the previous reports. 1–3 Although no case of TBE has been confirmed
in South Korea, human encephalitis cases with
In 2014, the most recent surveillance study unknown causes have been increasingly
was conducted to evaluate the prevalence of reported. TBE screening at the Korean Centers
TBEV and other tick-transmitted viruses for Disease Control and Prevention (KCDC)
(Powassan virus, Omsk hemorrhagic fever was started in 2006. As for undefined
virus, Langat virus, and severe fever with encephalitis cases or suspected TBE cases,
5
thrombocytopenia virus) among wild ticks. A blood and cerebrospinal fluid (CSF) samples
total of 21,158 ticks were collected by are required to be sent out to KCDC to
dragging at 139 sites in 6 provinces; H. perform enzyme-linked immunosorbent assay
longicornis was the dominant tick species (ELISA) and RT-PCR for TBEV. However, there
(83.04%, 17,570/21,158), while other tick are significant limitations of TBEV clinical
species, H. flava (15.68%, 3317), I. nipponensis surveillance in South Korea. First, TBE disease
(1.18%, 249), Amblyomma testudinarium awareness is quite low, and diagnostic
(0.05%, 11), and Haemaphysalis phasiana practice is limited in clinical settings.
(0.04%, 8), were much less common. TBEV Neurologists often take care of undefined
was detected by nested reverse transcriptase- meningitis/encephalitis cases, but they are
polymerase chain reaction (RT-PCR) in the completely unfamiliar with TBE. Second,
Andong, Uiseong, Daegu, and Yangsan areas. considering the short duration of TBE viremia,
The maximum likelihood estimation it is not easy to confirm the infection using
(estimated numbers of viral RNA-positive ticks blood and CSF samples collected at later
per 1,000 ticks) for H. longicornis, H. flava, and clinical stages. To better characterize the
I. nipponensis was 0.23%, 0.90%, and 8.02%, disease burden of TBE in South Korea,
respectively. On phylogenetic analysis, the serologic studies are required to evaluate TBE
TBEV strains identified in this study belonged prevalence in high-risk populations such as
to the Western subtype also. forest workers and farmers in the endemic
areas. At the same time, active surveillance
Even though no confirmed human TBE case with enhanced awareness would be essential
was reported in South Korea, TBEV might have
to find missed TBE cases.
been endemic in various localities and H.
longicornis, H. flava, and I. nipponensis would
be potential vectors of the Western subtype
TBEV.

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