First of all, lilium does not have to be near tulips to get the so-called TBV. The virus that causes color breaking in lilium is more accurately called Lily Mottling Virus or LMoV. It was commonly referred to as TBV because it resembled the color breaking of tulips. Also, tulips cannot catch the color breaking virus (LMoV) from infected lilies. If the color breaking shows all the way through on the underside (reverse), then it is infected with LMoV. Exactly how it became infected is anybody's guess. It may have been infected upstream from whoever your source may have obtained it from. Often times, if growing conditions are ideal and a lily is otherwise healthy and in good condition, it may not show symptoms of any virus. But the minute some growing condition becomes less that ideal or the lily becomes stressed, the symptoms show up.
The safest and easiest solution is to dispose of the infected plant before some vector transfers the virus to your other lilies. However, if you want to chose to 'wait and see' if it shows this same condition next year, then move it a considerable distance away as biting insects, both above and below ground, nibbling bunnies and rodents can transfer the virus. Be careful that you, yourself, don't transfer the virus through handling of this plant as humans are the biggest vector of all.
