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Chapter 2a: Virology

Figure 1: TBEV phylogenetic tree

Phylogenetic tree illustrating the relationships between representative members of the TBEV complex
(highlighted in red). Complete genome open reading frame sequences were retrieved from genbank and aligned
using the gins option in mafft v7.266. The tree was constructed with RAxML v.8.2.9 using the GTR+G model of
nucleotide evolution and 1000 bootstrap replicates. The resulting tree was visualized and edited in Figtree
v.1.4.1. All branches have maximum bootstrap support (not shown). The tree was midpoint rooted for visual
purposes only. The lowest clade (black) contains members of the divergent seabird tick-associated virus complex
(Meaban virus through Tyuleniy virus). We gratefully acknowledge the assistance of Dr John Pettersson
(Norwegian Institute of Public Health, Oslo) who prepared and supplied the tree.

where at least one flavivirus species is can infect a broad range of hosts and vectors
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endemic. Moreover, many flaviviruses have including domestic animals.
recently expanded their endemic areas, being Most of the known flaviviruses are transmitted
introduced to novel loci either on new horizontally between hematophagous arthro-
continents (West Nile virus, Zika virus, etc.) or
pods (ticks or mosquitoes) and their verte-
to areas with higher altitude or latitude (TBEV brate hosts. They are therefore considered to
2–3
as an example). For these reasons,
be dual-host viruses. Depending on the
flaviviruses pose an important threat to recognized arthropod vector, they are divided
public and animal health. Moreover, they into mosquito-borne or tick-borne viruses.
have high zoonotic potential because they
The term ‘arbovirus’ (an acronym from

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