COVID-19 diagnostic testing has been greatly scaled up from a few thousand tests per week back in early March to 2 million tests per week in early August. But the summer upsurge in COVID-19 diagnoses, hospitalizations, and deaths in the U.S. highlights the fact that we still don't have enough testing to provide individual Americans and health care professionals with the information needed to squelch the pandemic. A huge part of the problem is that most asymptomatic, presymptomatic, and mildly afflicted people don't know they're infected, even as they spread the virus to others while working, shopping, and gathering in...