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.
Sciencemag.org