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(LEAD) Recovered virus patients retest positive due to 'dead' virus fragments: experts

All News 13:49 April 29, 2020

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SEOUL, April 29 (Yonhap) -- South Korean health experts said Wednesday that recovered coronavirus patients may have tested positive again due to traces of virus fragments that have been inactivated.

As of Tuesday, a total of 277 people who recovered from COVID-19 have retested positive here, according to the Korea Centers for Disease Control and Prevention (KCDC).

The country's central clinical committee for emerging disease control said there was no live virus present in such cases, positively refuting theories like the virus being reactivated or reinfection.

They said that apparent reinfection cases came because fragments of the virus remained in their bodies and showed up in test kits.

Oh Myoung-don, head of the country's central clinical committee for emerging disease control, speaks during a press conference on April 29, 2020. (Yonhap)

The country currently uses a reverse transcription polymerase chain reaction (PCR) test for the COVID-19 virus that works by finding the virus's genetic information, or RNA, in a sample taken from a patient.

The experts said this PCR test is so sensitive that it can still pick up parts of the small amount of RNA from a cell even after the person has recovered from COVID-19.

"RNA fragments still can exist in a cell even if the virus is inactivated," they said in a press release. "It is more likely that those who tested positive again picked up virus RNA that has already been inactivated."

Oh Myoung-don, head of the committee, said the cases in which people retested positive were due to technical limits of the PCR tests.

The committee further said it is virtually impossible for the virus to be reactivated unless the COVID-19 virus causes chronic infections.

"The COVID-19 virus does not invade inside of the cell nucleus and combine with a patient's DNA," Oh said. "It means that the virus does not create chronic infections."

Oh further said the COVID-19 virus is different from diseases such as HIV and hepatitis B in which the virus stays dormant inside of a cell nucleus and later causes chronic infection.

Concerns have risen over chronic infections after several COVID-19 patients stayed in hospitals over two months before being cured.

The country reported nine more cases of the new coronavirus Wednesday, bringing the nation's total infections to 10,761, the KCDC said. It marked the 11th day in a row that the number of new infections stayed at 15 or below.

khj@yna.co.kr
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