Parts of Asia that relaxed restrictions without a resurgence in coronavirus cases did these three things

Between Jan. 19 and Feb. 18, South Korea confirmed a total of 31 cases, most of which were directly linked to travel to hot spots in China, according to data compiled by the WHO. In the weeks that followed, the virus spread to multiple cities across the country. New cases peaked on Feb. 29, when the country reported 813 new cases, bringing the total to 3,150, according to WHO data.

Total cases more than doubled by March 10, but Korean health officials rolled out an aggressive testing regime that processed tests for more than 259,000 people and confirmed more than 8,000 infections by mid-March, according to the Korean CDC. The U.S., by comparison, had tested roughly 22,000 people by then, according to the U.S. CDC at the time.

South Korea set up hundreds of walk-in and drive-thru testing centers, traced the origin of local outbreaks and isolated people who might have come in contact with the virus. The rate of infection plateaued at around 100 new cases per day for much of March and early April.