Map of places that Covid-19 infected have visited in S. Korea

Anyone know the source of this data?

I don't understand the map. I had expected some kind of heat map (based on say mobile phone traces of affected users).

That would actually be pretty cool (and privacy problematic) - I wonder if that's something the CDC requests from diagnosed cases.

Wow, that's quite a lot more than I expected. I wonder what it looks like in North Korea. Unfortunately, it is probably much worse

Ubiquitous mobile phone location tracking will be useful here

“Text COVID19 to get notified if you were in a place where Coronavirus was present”

Would be cool for someone to mash this up with something like location history. If you keep location history with any of the cloud providers (or your own devices if that's your thing), you could get your history via their relevant GDPR complaint or other take-out mechanism. Then you could intersect your path through space-time with the coordinates on this map.