EXTENSIVE contact tracing and isolation were key tools in controlling the spread of COVID-19 in Shenzhen, as shown in a study published at the Lancet Infectious Diseases, an authoritative medical magazine, April 27.

The study, jointly supported by the U.S. Centers for Disease Control and Prevention, and the Harbin Institute of Technology, Shenzhen and Pengcheng Laboratory in Shenzhen, utilized information from the Shenzhen Center for Disease Control and Prevention from Jan. 14 to Feb. 12.

Researchers analyzed data from 391 patients and 1,286 of their close contacts, and found that extensive contact tracing and rapid isolation of potentially infected individuals reduced the time that infectious people interacted with others in the community by two days.

The research and analysis by 22 Chinese and foreign scientists, thought to be the first of its kind in such a well-documented and well-tested set of cases, revealed that the COVID-19 index cases had symptoms for about five days on average before being identified, but that tracing and testing reduced this to about three days for infected contacts.

Among the contacts, household contacts had a particularly high risk of infection. Children, while less likely to develop severe symptoms, were infected at about the same rate as adults.

The report showed that early in an outbreak, before community infection is widely spread, epidemiologists can much more easily assess transmission dynamics by finding symptomatic people, and then tracing their recent contacts to see who got infected and who did not.

Moreover, the researchers found that some infected individuals accounted for many further infections, implying that such super spreaders could relatively easily reignite outbreaks.

These findings will help epidemiologists, pharmaceutical scientists and public health officials around the world shape their goals and policies to meet the challenge of the pandemic, the researchers say.

“The experience in Shenzhen may demonstrate the huge scale of testing and contact tracing needed to reduce the virus spreading,” said Ma Ting from the Harbin Institute of Technology. “Some of the strict control measures enforced here, such as isolating people outside their homes, might be unlikely to be replicated elsewhere, but we urge governments to consider our findings in the global response to COVID-19,” said Ma.(Han Ximin)