After spending ten days in an ICU (with happy hypoxia[1]), and seeing it hospitalise a member of my family for about a month, leave one almost bedridden for days and with a metallic taste in the mouth for weeks, and two others with cough/fatigue/completely no sense of taste, I'd've probably suspected something was up. Could I rule known diseases? Maybe not, but it'd have to have hit us usually hard and with an unusual set of symptoms.

[1] https://www.theguardian.com/world/2020/may/03/happy-hypoxia-...