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. Assuming that contacts with missing test results were not infected, the researchers estimated an attack rate of 11.2% (95% confidence interval [CI], 9.1 to 13.8) among household contacts and 6.6% (95% CI, 5.4 to 8.1) overall. Risk of infection was highest for household contacts (odds ratio [OR], 6.27; 95% CI, 1.49 to 26.33) and those traveling with an infected person (OR, 7.06; 95% CI, 1.43 to 34.91). Infection was as common in children as in adults (7.4% in children younger than 10 years; average, 6.6% in overall population). Mode of detection was known in 379 of the 391 patients. Of them, 292 (77%) were identified through symptom-based surveillance, and 87 were identified through contact tracing.

 

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