European Subtype Tick-Borne Encephalitis Virus Emergence In South Korea (2005 - 2014) Can Be Associated With Human Activity

Tick-borne encephalitis virus (TBEV) is the etiological agent of tick-borne encephalitis. TBEV is maintained in nature by the ixodid ticks Ixodes ricinus and I. persulcatus, which are its hosts and main vectors. The classification distinguishes three TBEV subtypes: Far Eastern, European (TBEV-Eu) and Siberian. Each subtype is characterized by its own range, reflected in its name. Nevertheless, numerous findings of TBEV subtypes in non-endemic areas have been reported. This phenomenon may be the result of virus introduction due to natural causes such as bird and mammal migrations. Detection of TBEV-Eu in South Korea in 2005 and in Siberia in the second half of the 20th century are significantly different from other cases of virus introduction. This paper presents the results of a comprehensive study including phylogenetic analysis, clusteron approach, establishing specificity of viral population dynamics, etc. The age of viral populations and the probable time of their emergence in non-endemic regions were determined. Using the example of TBEV-Eu in South Korea, we conclude that there is negative population dynamics of the virus after its introduction. This conclusion, in conjunction with several other features, indicates that human activity played a pivotal role in the TBEV-Eu introduction into South Korea and Siberia.