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Extensive contract search, case isolation, and testing can reduce the spread of the new coronavirus and help control the COVID-19 outbreak, a study in China suggests.
However, researchers at the Harbin Institute of Technology in Shenzhen, China caution that the impact of contact tracing to quickly isolate people who might be infected with the 2019 coronavirus disease (COVID-19) depends on the identification of asymptomatic cases.
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Published in The Lancet Infectious Diseases, the study of 391 cases and 1,286 of their close contacts found that contact tracing reduced the time people were infectious in the community for 4 weeks in Shenzhen, China.
According to the In Shenzhen results, authorities identified who to isolate based on their contact with confirmed cases, as well as isolate people who already had symptoms, the researchers said.
The new study found that contact tracing increased the rate at which new cases were confirmed within 2 days, an average of 5.5 days initially, decreased to 3.2 with contact tracing.
It also reduced the amount of time it took to isolate infected people by 2 days, from an average of 4.6 days to 2.7.
The researchers said there were only three deaths in the study group during the study period.
“COVID-19’s experience in Shenzhen City can demonstrate the large scale testing and contact tracing that is needed to reduce the spread of the virus,” said Ting Ma of the Harbin Institute of Technology in Shenzhe.
“Some of the stringent control measures applied here, such as isolating people outside their homes, are unlikely to be replicated elsewhere, but we urge governments to consider our findings in the global response to COVID-19,” Ma said.
To achieve similar results, the researchers observed that other countries could combine near-universal testing and intensive contact tracing with social distancing and partial blockages.
“Although blocking measures were not introduced in Shenzhen until the end of our study period, the Wuhan blockade could have significantly restricted the spread of the coronavirus to Shenzhen,” Ma said.
For the current study, the researchers analyzed data from 391 people diagnosed with COVID-19 after they showed symptoms, and 1,286 from their close contacts.
Contacts were tested regardless of whether they had symptoms to identify infected individuals who were asymptomatic.
The data provided information on the type of contact most likely to lead to transmission.
Close contacts were defined as people who shared a home with infected patients up to 2 days before they started showing symptoms, or interacted with them socially by traveling or eating together.
For people who were isolated because they showed COVID-19 symptoms, it took an average of 4.6 days to isolate themselves after the first signs of infection. Tracking contacts reduced this to an average of 2.7 days, the researchers found.
For people diagnosed with COVID-19 after being tracked and examined by contact (87 people), a fifth (17 of 87 people) had not yet developed any symptoms, and 30 percent (25 of 87) had no symptoms. fever, they said.
The length of time a person remains infectious is not yet known, but reducing the amount of time infected people interact with others appears to have helped reduce the spread of the virus, the researchers said.
The researchers highlight several limitations to their study, including the fact that it is impossible to trace every potential contact an individual has.
Therefore, contact tracking focuses on close contacts who are most likely to be infected.
They point out that some infected travelers to Shenzhen may have been lost if only the tests were done due to symptoms such as fever.
Their contacts could also have been lost if they were asymptomatic, because the PCR test is not sensitive enough to detect every case, according to the researchers.
