We often here in Japan that a high percentage of new patients are 経路不明 meaning cannot trace how they got the Corona Virus. Either because they do not know, or that the patients do not want to tell.
With all due respect to Privacy laws in Japan, I think the government can do more to track and analyze.
First and most obvious is Cellular Phone location. Government can get cellular phone location of patients, track their location and try to find common places and source.
Second, which is probably less effective, but is interesting for me is genomic tracking of the Corona Virus. Apparently, the mutation of the virus and analysis of that can track the source and spread. Twitter and internet are discuss and quote Trevor Bredford’s twitter and analysis.
Looking at some genomic analysis of the virus in patients in Japan, can see clearly the second wave coming from Europe, US and other countries