I went to CES this year, and a week and a half after (a typical incubation time for Covid-19) I started coming down with a strange lower respiratory illness that involved joint aches (my sacroiliac joint in particular, which I think I had stressed horribly the past year, suddenly became excruciatingly painful as I got sick to the point where I couldn't sleep), and intense on/off fevers/chills that lasted way longer than I am used to... and yet my cough was unproductive, I had no sinus or other involvement (which I always get), and I simply didn't have any other symptoms I am used to with a flu; it essentially seemed like "pneumonia maybe but with the wrong progression".

Regardless, I was knocked out for a while due to the fevers and lack of sleep. When I was just sort of getting better, I was visited by a coworker who, two weeks after he saw me for a day--and he notably spent most of that day with me, including multiple meals: we are two people at the top of a small company and I had been sick a while, so we had a lot to catch up on)--got sick with what we later determined was Covid-19 by positive test (but like, weeks later, at which point I hadn't been sick for a long long time, so there seemed no point in trying to use a viral test on me).

FWIW, we have good alternative explanations for where he got Covid-19, where I got sick with a shorter incubation time (involving me getting very little sleep while traveling to a handful of back-to-back events), and why I had joint pains (a particular series of flights and car trips that were similar to what I think first caused me issues a year ago... I didn't understand this until a month later, btw: I am changing my style and quantity of travel); but I really wish it were easy for me to quickly get an antibody test to see whether I have already had this (though that still won't ever tell me for sure as I could have had an asymptomatic case more recently... le sigh).