Amid these dire trends, South Korea has emerged as a sign of hope and a model to emulate. The country of 50 million appears to have greatly slowed its epidemic; it reported only 74 new cases today, down from 909 at its peak on 29 February. And it has done so without locking down entire cities or taking some of the other authoritarian measures that helped China bring its epidemic under control. “South Korea is a democratic republic, we feel a lockdown is not a reasonable choice,” says Kim Woo-Joo, an infectious disease specialist at Korea University. South Korea’s success may hold lessons for other countries—and also a warning: Even after driving case numbers down, the country is braced for a resurgence.

Behind its success so far has been the most expansive and well-organized testing program in the world, combined with extensive efforts to isolate infected people and trace and quarantine their contacts. South Korea has tested more than 270,000 people, which amounts to more than 5200 tests per million inhabitants—more than any other country except tiny Bahrain, according to the Worldometer website. The United States has so far carried out 74 tests per 1 million inhabitants, data from the U.S. Centers for Disease Control and Prevention show.

South Korea’s experience shows that “diagnostic capacity at scale is key to epidemic control,” says Raina MacIntyre, an emerging infectious disease scholar at the University of New South Wales, Sydney. “Contact tracing is also very influential in epidemic control, as is case isolation,” she says.