i am no expert on orchid virus, but i don't recall ever seeing this sort of look while reading up on them, most of the virus pictures i have seen show a definite ring-like circle shape, or actual dead spots, not just discoloration, and the discoloration i have seen shows a yellow patch... my guess is this is simply an older leaf, and at some point it got too much sunlight? the virus photos i have seen are the 'ring spot' and 'mosaic' virus. i'm not really aware of any others, but your orchid does not seem to have those two...