While there’s something to this, I don’t think people are properly calibrated on how bad a new disease can be. Like, it’s totally normal and reasonable for a new disease introduced into a population to kill 80%. It’s not super common but not super uncommon either. I guess what I’m saying is that permanent, brutal sequelae not seen in diseases which have reached equilibrium with the host population would be completely within the range of expectations.
This appears to be incorrect. It isn’t known if a bad case of the flu gives you permanent brain damage.