I have a problem (I think) on a cymbidium orchid. I am not sure if this is the mosaic virus or not. It looks a bit like it from pictures I have research, but I really need to know as I believe it is incurable and likely to spread. Can anyone help? Thanks.
This does not look like mosaic virus to me - the size and lack of intensity of the blackened areas hints at something other than a viral infection. These are random areas of fine spots which don't follow the usual pattern of how a virus appears and spreads on cymbidiums and other orchids.
This image below is far more typical - with yellowing and black streaking occurring along the length of the leaf rather than a random patch of small dots.
What your leaf seems to have looks to be more like a fungal issue - a mildew or mould that is more superficial - or a cultural problem.
Whatever it is, remove the affected leaf by cutting it off at the base and dispose of it carefully. Keep a watch for any further development on other leaves and by all means come back to us if you spot further symptoms.