When the cluster outbreak of the new coronavirus (COVID-19) occurred at a call center in Guro-gu, Seoul, all the five employees at the call center who are members of the Shincheonji Church tested negative.

However, experts said they could not rule out a possibility that the Shincheonji members may have tested negative because they had already recovered from the virus infection.

According to the Korea Centers for Disease Control and Prevention (KCDC), the call center in Guro-gu had 134 confirmed cases as of 0 o’clock Wednesday, up by five from the previous day. Eighty-two of them live in Seoul, followed by 33 in Gyeonggi Province, and 19 in Incheon.

Among the employees of the call center, the tests on the five who are members of the Shincheonji religious group came negative.

The health authorities’ epidemiological investigation could not confirm the first infected person within the call center in Guro-gu.

Lee Hyuk-min, director of infection control affairs at the Korean Society for Laboratory Medicine, said an antibody testing could be used for an epidemiological study on a case like the Guro call center, at a YouTube show Tuesday by K-Healthlog, a channel operated by The Korea Doctors’ Weekly.

KCDC is known to be developing a test method to detect an antibody against COVID-19.

“Antibody testing can check the viral infection by targeting an antibody that develops after a virus gets into a human body. But the entry of a virus does not create an antibody right away,” Lee said. “So, we use antibody testing in the late-stage viral infection to look at epidemiologic linkage rather than in the early-stage infection.”

Lee picked the cluster infection at the Guro call center as a good case to apply antibody tests.

“The call center produced so many COVID-19 patients, but all the five Shincheonji believers tested negative. Antibody tests can check whether the five had been infected with the virus,” he emphasized.

Lee said he heard KCDC has completed the preparation for COVID-19 antibody testing and was in the final review to use it in clinical settings.

Lee Wang-jun, the leader of the Working Group of the Korean Hospital Association's COVID-19 Emergency Response Headquarter and chairman of Myongji Hospital, said the Shincheonji members at the Guro call center might have been infected with the virus.

“Even though they tested negative, they may have been infected and recovered naturally. We can check this with antibody testing,” Lee said.

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