Don't know if folks have seen this. I plucked it out of a reddit forum this morning, but I think I may have seen it yesterday.
So, the argument these researchers are making is based on what they're calling "excess" in the CDCs ILI (Influenza Like Illness) data. If you go to my other post in this forum ("US Coronavirus - when did it get here, exactly?), you'll see I'm making exactly the same argument. ILI data in the US takes a big jump starting in the November timeframe and my bet is that part, or maybe even a large part, if that ILI increase is COVID-19.
If you're interested in looking at the data yourself, ILI can be found here:
Scroll down to the ILINet section and check out the graph.
Another interesting page is the ILINet State Activity Indicator. This page merges ILI data with GIS (Geographic Information Systems) and shows how ILI is moving through each state week over week.