I'm having a hard time finding the link, but a couple weeks ago I found something showing the mutation/strains of Corona/COVID-19 and even then there were already 8 distinct strains IIRC.
Slate Star Codex, which I've written about before in my erisology thread, has probably the best info, data, and takes on Corona available on the internet.
Check a few of these posts out to get a sense, then keep an eye on the site - there's a new corona update just about every week:
March 2: CORONAVIRUS: LINKS, SPECULATION, OPEN THREAD
March 19: CORONALINKS 3/19/20
March 23: FACE MASKS: MUCH MORE THAN YOU WANTED TO KNOW
March 27: CORONALINKS 3/27/20: WE’RE NUMBER ONE
April 10: CORONALINKS 4/10: SECOND DERIVATIVE
This is a site where it's definitely worth looking through the comments. You'll find thoughts on and links to all kinds of stats, data visualizations, and studies (on any topic, but on these posts it's pretty much all corona, all the time).
Which explains why people recovered are testing positive again. Multiple strains at work.