Tkachev et al.
Genetic diversity and geographical distribution of the Siberian subtype of the tick-borne encephalitis virus
Ticks Tick Borne Dis., in press, doi.org/10.1016/j.ttbdis.2019.101327

The TBE virus is currently divided into three main subtypes – the European (TBEV-Eu, the Far Eastern (TBEV-FE) and the Siberian subtype (TBEV-Sib), and two putative new subtypes have recently been added – the Baikal and the Himalayan subtype.

The Siberian subtype is the most common subtype and has been detected in all regions where the TBE virus was identified except for Western and Central Europe. TBEV-Sib is regarded to cause less severe disease, compared to TBEV-FE, but may cause chronic infections. The pathogenicity within a subtype may vary and may be attributed to certain lineages. The TBEV-Sib has a higher genetic variability compared to TBEV-Eu and TBEV-FE.

TBEV-Sib contains at least five lineages including a newly described Bosnian lineage.

  • The Zausaev lineage is the most common one and is distributed from Eastern Europe to Eastern Siberia.
  • The Baltic lineage is found from Eastern Europe to Western Siberia.
  • The Vasilchenko lineage is found from Western Siberia to the Far East.

Two other lineages have restricted areas. Based on sequence data of the E gene, the geographic spread of TBEV-Sib was divided into fifteen regions.

  1. In detail, the Zausaev lineage was found in North-Western and Central Russia, the Urals, Western and Eastern Siberia, Transbaikalia, and Central and Middle Asia:
  2. The Baltic lineage was detected in the Baltic region, Northwestern and Central Russia, Urals, and Western Siberia.
  3. The Vasilchenko lineage was found in Central and Middle Asia, Western and Eastern Siberia, Transbaikalia, Mongolia, China, and the Far East.
  4. The recently described rare Obskaya lineage was detected only in Western Siberia.
  5. The novel Bosnia lineage was detected in the southern parts of the TBE virus distribution area: Bosnia, the Crimean Peninsula and Central and Middle Asia (Kyrgyzstan, Kazakhstan).

A dendrogram of the TBE virus strains illustrates the evolution of the lineages and a figure shows the geographic distribution of the lineages including the new Bosnian lineage.

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