When testing is scarce it is used as a clinical tool to help make decisions about treatment. For example: patient has pneumonia. If its bacterial pneumonia a co

When testing is scarce it is used as a clinical tool to help make decisions about treatment. For example: patient has pneumonia. If its bacterial pneumonia a course of the right kind of antibiotics will be very helpful. If its COVID, those antibiotics won't do anything, and the patient may not get the therapies they really need. Once testing becomes more available, doctors use it to rule out COVID even on patients who aren't very sick, to help make sure they those patients aren't spreading it, instead of just making treatment decisions. Ideally once testing capacity gets high enough we could start testing every contact of an infected person, or just randomly sample people.