https://www.sciencedaily.com/releases/2020/05/200526091413.htm

The COVID-19 outbreak was identified in both South Korea and in the United States on Jan. 13. As of May 22, South Korea had 11,142 cases and the United States had 1,571,617. From day one of the spread of the virus, South Koreans received text messages whenever new cases were discovered in their neighborhood, as well as information and timelines of infected persons' travel.

In a new National Bureau of Economic Research (NBER) working paper, researchers combined detailed foot-traffic data in Seoul from South Korea's largest mobile phone company with publicly disclosed information on the location of individuals who had tested positive. The results reveal that public disclosure can help people target their social distancing and this proves especially helpful for vulnerable populations who can more easily avoid areas with a higher rate of infection.