The United States leads the world in COVID-19 deaths but lags behind many countries — both large and small — in testing capacity. That could soon change.

At the end of August, the US Food and Drug Administration (FDA) granted emergency-use approval to a new credit-card-sized testing device for the coronavirus that costs US$5, gives results in 15 minutes and doesn’t require a laboratory or a machine for processing. The United States is spending $760 million on 150 million of these tests from health-care company Abbott Laboratories, headquartered in Abbott Park, Illinois, which plans to ramp up production to 50 million per month in October.

The tests detect specific proteins — known as antigens — on the surface of the virus, and can ident