Hello; Let me be more clear. I think the fact so many of the infected do not have symptoms caught the medical folks by surprise. They started out fighting the last war so to speak and could not figure in that odd factor because they were not aware of it for a while. ( well I guess the Chinese doctors could have had a clue earlier but they were not allowed to share in a timely manner.)The bigger problem with this virus has been so many infected do not have symptoms. Thai allowed the virus to become widespread as there was not a trail of actually sick people to follow
I guess contact tracing is a standard practice which has been in use for a long time. Like any tool it can be effective under the right conditions, but I suspect not so much right now.