2021.01.04 16:57:51 (1346123688010158080) from Daniel J. Bernstein, replying to "Peter Todd (@peterktodd)" (1346106387395473409):
Random examples from Taiwan: https://www.cdc.gov.tw/En/Bulletin/Detail/OYA5JuINJwUU90QHA6I67w?typeid=158 from February 2020 says "Taiwan identifies source of infection for 19th case"; https://www.cdc.gov.tw/En/Bulletin/Detail/tlyAMFhAVSCMoCyT_A8ISg?typeid=158 from April 2020 says "The CECC continues to investigate related contacts of the case to identify the source of infection".
2021.01.04 15:45:13 (1346105406892822532) from Daniel J. Bernstein:
Featured in today's edition of "See how country X is _not_ doing what the successful countries are doing": https://www.citizensinformation.ie/en/health/covid19/contact_tracing.html says that X traces contacts of an infected person P back 48 hours. Maybe finds infections caused by P, but won't find the moment that P was infected.
2021.01.04 15:49:06 (1346106387395473409) from "Peter Todd (@peterktodd)":
Do you have sources for examples of "successful" countries that contact trace further back in time?