The disease casually mentioned (https://en.wikipedia.org/wiki/Encephalitis_lethargica) in the article is worth looking into as well - a ?virus? that causes coma, that appeared, wreaked havoc (affected ~1M people and killed half) for a decade or so, then disappeared
Yeah, with the possible connection to the Spanish Flu epidemic this gives one pause when considering long covid and covid's neurological effects in general
