The debate about when and whether the world can reopen keeps coming back to testing. If only we could test everyone all the time, the logic goes, we could isolate the ill and everyone else could go back to school, work and life as we once knew it.
Sadly, that’s not quite right. The prerequisite for reopening is better tests, not just more tests.
A “good test” has three properties: It’s rapid (like less than an hour), accurate and widely available. Only with all three can it be used to screen people before they go to the office, get on an airplane, or attend a class or conference. And only then — barring an effective vaccine — can authorities safely allow people to do all those things.