Yoshii et al.
A retrospective epidemiological study of tick-borne encephalitis virus in patients with neurological disorders in Hokkaido, Japan
Microorganisms. 2020;8(11):1672. doi: 10.3390/microorganisms8111672.

The first case of confirmed TBE in Japan was reported in 1993. Since then, only four additional cases have been notified in areas of Hokkaido (between 2016 and 2018). However, TBE virus could be isolated from dogs, wild rodents and ticks, and high seropositivity rates were shown in epizoological studies in Hokkaido.

An extensive retrospective epidemiological study has now been carried out among patients (2000 individuals who fell ill between 2010 and 2018) with neurological disorders in Hokkaido. Some sera were detected which were either positive in an IgM and/or IgG ELISA and showed neutralizing activity (and missed neutralizing activity against Japanese encephalitis virus).

In addition, a serological survey was conducted in healthy volunteers in Yuni town in central Hokkaido. Among 246 samples, one serum was detected which was positive in an IgG ELISA and showed neutralizing activity.

In conclusion, these data indicate underdiagnosis of TBE in Japan.

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