There is no reason for Contact Tracing. By the time a person has symptoms, and the Tracers interview him, and go to everyone he was in contact with, the "contacted people" will have either gotten over it or had no symptoms at all (meaning they cannot be identified as the person who gave it to the sick person). And if the "contacted person" does get sick enough to seek a doctor's help, he will thus already have been found! So there must be some other reason for this "Contact Tracing"....