Just understand a few things:
1) December/January/February are peak flu months. We see a LOT of it and this past year was particularly high prevalence. So, when you consider the thousands upon thousands of people that actually had the flu, most of them are going to look back and go "wow, this could have been Covid". But, more than likely, it was the flu.
2) Along with #1, just because Covid now seems to have been found back in December, it most definitely wasn't very common or widely circulating. There is no question about what we are seeing now. We weren't seeing that in January and February. So there may have been a "handful" of cases where it started, but there's no way it was anywhere near as common as the flu as our hospitals would have seen the clinical symptoms we see now which are very different than typical flu.
In other words, if you were sick back in January and even February, it was very likely the flu and not Covid unless you had the typical symptoms we are now seeing with Covid (i.e. loss of taste and smell).