I wonder if this is a continuous effect that eventually fades away, or a one-time permanent “debuff”. Did you have to practice a lot to get back to your level, or did it resolve by itself?
It was just at the end before the summer break that I managed to do the same numbers as before when running and similar. And this was with the same hours per week of practice, though of course with much less intensity due to the exhaustion.
Of course there's no control-me, so can't say if there was a permanent effect as such.
I suspect that of a pair of identical people who spent 1 hour in the gym every day for a lifetime, one of whom got a long term viral infection, the infected one would never again match the performance of the uninfected.
some issues can be recovered from completely, some are permanent.
So yes, there is no guarantees.
In some people it can trigger an autoimmune disease as well, that's also for life.