[Goose]

One might wonder why not just test everybody (assuming that was possible) ? The problem is that these tests have limited sensitivity. Someone could have the virus but not at a high enough level for the test to detect it. They aren't sick now but will be later. That is also why immediately testing everybody right after they are exposed to the virus somehow will miss lots of people who will actually get sick. It is just a waste of effort. Since these are new tests, we really don't know what the sensitivity is and how soon after exposure the test will pick up active disease. We probably know more than we did before, but since we use a different test than China used, YMMV. Deciding who to test and when to test is not a simple as it may first appear.

[Goose]

One might wonder why not just test everybody (assuming that was possible) ? The problem is that these tests have limited sensitivity. Someone could have the virus but not at a high enough level for the test to detect it. They aren't sick now but will be later. That is also why immediately testing everybody right after they are exposed to the virus somehow will miss lots of people who will actually get sick. It is just a waste of effort. Since these are new tests, we really don't know what the sensitivity is and how soon after exposure the test will pick up active disease. We probably know more than we did before, but since we use a different test than China used, YMMV. Deciding who to test and when to test is not a simple as it may first appear.