Isolation and contact tracing—which are now key topics as US officials discuss plans to open up the country—helped control the spread of COVID-19 in Shenzhen, China, according to a study published yesterday in The Lancet Infectious Diseases.In the first known coronavirus research of its kind, researchers studied 391 COVID-19 patients and their 1,286 close contacts—identified through symptomatic surveillance and contact tracing from Jan 14 to Feb 12—to characterize disease course, transmission, and the effect of control measures.After 622 of 653 close contacts with known quarantine dates were followed for at least 12 days, 98 tested positive, and one had presumed infection.