I'm no expert and everything that follows is anecdotal, so take it for what it's worth (not much, in other words).
I have a strong feeling a lot more people have had COVID than anyone can know. And I think COVID has been here longer than the experts can find evidence of.
What I've seen:
My mother passed away last December which means a very large extended family was together more than once before and following the holidays. My family consists of four sisters, four brothers, eight spouse and 22 grand-kids. Add in more spouses and great-grand-kids and you have a crowd even before the hometown gets involved at the wake, the funeral, the funeral dinner... In addition, we live all over the country and some of of us had made trips abroad.
One of my sisters, a nurse, had "something" in September thru November that antibiotics/steroids/etc could not kick. Her doctor couldn't identify what it was at the time. Looking back she can check all the boxes for COVID.
Throughout December and January we all had colds and flu that were worse than we normally have.
My wife lost here senses of taste and smell in December.
I didn't lose taste or smell but felt run down and had lingering cold symptoms for 2 or 3 months.
The same with the rest of my clan. Each branch had their own version of "something" and it all looks, at some level like COVID.
It's interesting that blood serum studies are coming out showing that COVID was in Iowa in December last year already. It supports my theory a little, at least.
Since this started my family has had the opinion that the most interesting numbers would be how many people already had the antibodies prior to this being declared a pandemic. I think a fairly large portion my extended family does.
For the record: I'm not one of the people claiming natural herd immunity will stop this thing but we already may be closer than anyone will ever know.
All that said: My household wear our masks, wash our hands, use hand sanitizer, stay home and do all the stuff we have told to do to stop this thing. And we will get vaccinated as soon as we possible can, when it's our turn. The teachers (2), engineers (1 working and 1 in college), our resident chemist and myself will all be in different phases of the rollout. I suggest you all do the same.
As I started this...
This is all just observation and conjecture. There is still a lot to learn about this little buggard.
Stay safe everyone.