How many tests do we need in order to safely relax social-distancing measures, reopen nonessential businesses and schools, and allow large gatherings? According to the Morgan Stanley analyst Matthew Harrison and the Harvard professor Ashish Jha, we should be conducting a minimum of 500,000 tests a day. One of the authors of this article, Paul Romer, has called for the capacity to run 20 million to 30 million tests a day. Even this has been criticized as insufficient for the task of identifying enough of the asymptomatic spreaders to keep the pandemic in check.

Current guidelines from the Centers for Disease Control and Prevention give priority first to hospitalized patients and symptomatic health-care workers, then to high-risk patients, specifically those over 65 and those suffering from other serious health conditions, with COVID-19 symptoms. Under this system, asymptomatic individuals are not tested, even if they had contact with people who tested positive.

This is an enormous mistake. If we want to control the spread of COVID-19, the United States must adopt a new testing policy that prioritizes people who, although asymptomatic, may have the virus and infect many others.

Read: How the pandemic will end

We should target four groups. First, all health-care workers and other first responders who directly interact with many people. Second, workers who maintain our supply chains and crucial infrastructure, including grocery-store workers, police officers, public-transit workers, and sanitation personnel. The next group would be potential “super-spreaders”—asymptomatic individuals who could come into contact with many people. This third group would include people in large families and those who must interact with many vulnerable people, such as employees of long-term-care facilities. The fourth group would include all those who are planning to return to the workplace. These are precisely the individuals without symptoms whom the CDC recommends against testing.

Not testing suspected COVID-19 patients will not harm those patients. Because we do not have any treatment targeted for the new coronavirus, confirming an infection generally does not change the way a patient’s symptoms are treated. Patients suspected of having COVID-19 should be presumed to be infected and receive care accordingly. Symptomatic patients should be tested only in the rare case where a positive test would meaningfully change what type of care is delivered.

To shift the focus of testing away from the sickest patients and toward the people most likely to spread the coronavirus, we will have to conduct millions of tests a day. Millions of health-care workers in the United States are in positions that may expose them to infection: physicians, nurses, respiratory therapists, midwives, pharmacists, phlebotomists, hospital cleaners, and others. By one estimate, 3 million people work in grocery stores. To screen everyone in these two groups once a week will require about 1 million tests a day. We currently lack the infrastructure for that. And that is before we add the approximately 800,000 police officers, 290,000 bus drivers, and 60,000 sanitation workers—and patients without any symptoms in the health-care system. We will need millions more kits to test asymptomatic potential super-spreaders and people planning to return to work. Taking a sample from seemingly well people just once isn’t enough; effective surveillance over time requires repeated testing.