The Korean model is test a lot, and quarantine those found infected. But that is just the beginning. The real effective tool is tracking down where the infect

The Korean model is test a lot, and quarantine those found infected. But that is just the beginning. The real effective tool is tracking down where the infected person had been by examining cell records, credit card records, interviews and determine where the infected person had been at for a few days before infection was confirmed. Once the recent movements of an infected person is compiled, the list of location/time is blasted out via app and also main stream media. This public disclosure is important as infected person might have visited a mall or a theater, making it impossible to contact each of possible contacts individually. Big malls/theaters have closed for a few days after a visit by an infected person is found. After deep cleaning of a few days, it reopens. Some articles that explain better are below. How Korea got a fast start with testing for coronavirus: https://www.reuters.com/article/us-health-coronavirus-testing-specialrep/special-report-how-korea-trounced-u-s-in-race-to-test-people-for-coronavirus-idUSKBN2153BW https://www.reuters.com/article/us-health-coronavirus-testin... Extensive contact tracing has slowed viral spread in Korea: https://www.nature.com/articles/d41586-020-00740-y https://www.nature.com/articles/d41586-020-00740-y But all of above is possible only with a lot of testing, free when ordered by a doctor due to possible exposure.