My six year old cat suddenly got sick and it turns out he has FLV, and I just can't wrap my brain around this. He's been tested for it multiple times and was vaccinated against it before I got him, and he's had his boosters. He's so sick he'll probably die, and he's only six years old. W.T.F. Is this a known thing that can happen, or have I slipped in to the fourth dimension somehow?