It's not a virus, and it's not caused by an almost invisible scratch.
I don't know this model of phone but, experience with a Cherry Orbit (rebadged Gigabyte GSmart G1310) suggests that it could just be a dirty screen. Problems with the Orbit include spurious screen taps and one time even one half of the screen went dead - these are all fixed by cleaning.
Clean the screen thoroughly, paying careful attention to the gap around the edge of the screen - scrape the gap with a piece of plastic, or even a finger nail.
If that doesn't fix it, then I would guess that it is a hardware fault.