> in China they have been using widespread facial recognition technology to track who has been near who. From this you can download an app and be informed if so

> in China they have been using widespread facial recognition technology to track who has been near who. From this you can download an app and be informed if someone you have been near has it. You're severely overestimating the surveillance capabilities of Chinese companies. When a new case is discovered, the government obtains their itinerary by asking them where they went and looking up which long-distance transport they used (tickets for that are tied to government ID, which is checked before boarding). When someone wants to look up whether they were close to someone infected, they can use their ID number to check whether they were e.g. in the same train car, or they have to verify for themselves whether they went to any of the same places. The process is significantly more manual than the pervasive location tracking via facial surveillance you imagine. What the companies you list could do is to allow everyone who has been confirmed infected to publish their location history, and compare against everyone else's. Using self-reported symptoms instead of confirmed cases would lead to a panic, since most people with a cough right now are infected with something other than the coronavirus.