People in positions of authority are talking about getting to a place where we can identify people with Covid-19 symptoms and a positive active virus test result. They then propose "contact tracing" to find out from whom they may have contacted the virus and to whom they may have passed it along. I doubt that will be possible, for two reasons.
First, something like 45% of those who have the disease never are sick, but are nevertheless contagious. Short of testing everyone every week or two, how will you pick these up? Second, people who ride crowded public transportation - subway cars or buses - have no idea who they're riding beside or in front of; whose hand held the strap they're now hanging onto before they boarded.
Add those two together and contact tracing will only work for those who commute alone in their car and are face-to-face with a limited number throughout the day. Imagine trying to do contact tracing for a barber who takes walk-ins, or a cabbie who's flagged down by cash fares he encounters a single time. Or someone who works the counter at McDonalds or the DMV. Contact tracing is not feasible.
