The ecology of the tick vector, which feeds only occasionally and is relatively immobile, the rarity of infected ticks, implying that the probability of multiple strains co-infecting the same tick must be low, the short mammalian viraemia and high mortality rate, are all plausible factors that would explain that no recombination has hitherto been reported in TBEV [14] . For recombination to occur, Table 4 . Times of origin (in years before 2008) for selected clades in the phylogenetic tree of Tick-borne encephalitis virus, obtained from the BEAST inference 4 based on a large Esequences dataset. a vector can become infected with multiple strains during cofeeding in close proximity on the host skin with other ticks carrying different strains. Co-infection is then mediated via the tick saliva [60] . Alternatively, ticks can engage in multiple feeding on viraemic hosts that have been previously infected with different strains [14] . For both situations, sheep are an ideal milieu for recombination to occur when they are fed upon by several vectors carrying both W-TBEV and LIV strains. Indeed, unlike TBEV, LIV can induce a high-titer viraemia in sheep which enables tick re-infection during bloodsucking [8, 11] .