We have a much firmer foundation of understanding monkeypox and it’s long term effects
You might be thinking of the 1889-90 "flu" pandemic which has been theorized to be from a coronavirus known now as OC43, but it's not certain.
Monkeypox isn't new. There have been hundreds of human infections since the 1950s before this recent outbreak, and it is closely related (enough for complete-cross immunity) to the other orthopoxes, which are some of the most studied viruses ever. So we know a fair bit. Pox viruses do not cause a chronic and permanent infection. A person usually either recovers and becomes immune, or dies.
Having had a doctor write me off as a hypochondriac because of physical anxiety I was experiencing due to a toxicity issue...I can safely say your medical beliefs are potentially dangerous to others.