It's not a virus. I agree with the others that it looks like a leaf spotting fungus. That type of fungus doesn't kill orchids but it looks unsightly and it can spread. You can reduce the spreading with good air circulation, keep some space between plants and don't wet the leaves in the evening. Also using a fertilizer that contains calcium and magnesium will help build stronger leaves that resist fungus. If your fertilizer doesn't contain calcium, use a calcium/magnesium supplement a couple times a month during the growing season.
To check for spider mites, wipe the underside of the leaves with a damp, white paper towel. If you see tiny red dots on the towel, then you have spider mites.
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