It would be nice if some scientist was interested enough to scan the of brains of some whirling discus with an electron microscope to see if they could find a similar herpes virus.
I can see the incentive to do the research in tilapia. They are a major food source and there was a huge financial incentive for them to do this research.
There's not any financial incentive with discus. It would be strictly an academic endeavor to know if whirling in discus is a viral encephalitis.
It wouldn't surprise me at all if a herpes virus encephalitis was discovered to be the cause of whirling disease in discus.