What's wrong with it?
 

It is a present plant form a friend. There are a sunburn scar and some purple changes on the new leaves. The changes are flat and are only on the upper surface. I have separated it from my other plants and am wonder that it is a sign of virual infection. Any recommendation is welcome! Thanks.

You really cant say its a virus unless you test it. Testers are cheap @$10 on Ebay...
It looks like fungus infestation. You are right to isolate it from the other plants...

How does the rest of the plant look? This particular leaf looks like it's been around for a while, with evidence of old wounds and cracks. I'm assuming the rest of the leaves are healthy. Chids shed leaves periodically, especially from older pseudobulbs. This leaf looks like it's worn out from injury and sunburn, and it will probably shed naturally in the near future. Due to the questionable spotting I'd play it safe and slice off this leaf, dab the cut with cinnamon, and keep it dry for a few days. Having said that, I would recommend isolation and a virus test if the other leaves are showing the same type of spots.

I would bet on the dark blotches being areas of almost-sunburn, not quite enough to get the necrotic spot and bleaching.

Virus home test kits are approximately $5 each at Agdia when you buy 25 kits. Guessing will fool you !!!

https://orders.agdia.com/InventoryD....ribute_Size=25

That looks a lot like sunburn

My vote is sunburn and also an older leaf.

Ditto sunburn :)

Thanks all.
Here is an enlarged image. In fact, I am worried about the purples along the vein. The leave is injured due to a typhoon hitting. The other leaves do not have such purple changes. Virus test is also expensive here, so I do not plan to order a test.

It simply sounds like you have one old beat-up, sunburned dying leaf. I wouldn't fret about it. It's normal to have one or two leaves die off every once in a while. You can let nature take it's course or cut it off and treat with cinnamon. :)