Recovered Covid-19 patients’ testing positive result from ‘virus fragments’

Kwak Sung-sun  Published 2020.04.29  15:33  Updated 2020.04.29 15:33


The reason 263 Korean people’s testing positive after recovery from the new coronavirus seemed to have been not because they contracted the virus again, but because remaining virus fragments were detected, health experts said.

The Central Clinical Committee for Emerging Disease Control, composed of physicians and experts treating Covid-19 patients in the nation, held a news conference at the National Medical Center on Wednesday to explain the possibility of the coronavirus reactivation or reinfection.

Oh Myung-don (second from right), head of the Central Clinical Committee for Emerging Disease Control, speaks at a news conference at the National Medical Center on Wednesday.

Oh Myung-don, who heads the committee, said the reactivation of the coronavirus is impossible because the Covid-19 virus does not cause chronic inflammation by going through a latent phase after invading the host gene.

“If we look at the results of the coronavirus (HCoV-229E) study on humans or the current Covid-19 virus (SARS-CoV2) study on animals, the immunity in vivo is maintained for more than one year after the first virus infection,” Oh said. “Thus, it is improbable that a person could contract another coronavirus.”

The panel also noted that the Covid-19 infection and the viral proliferation occur in respiratory epithelial cells, which means that viral RNA fragments may exist in epithelial cells even after the virus is inactivated.

“It seems that the virus’s RNA could have been detected in the PCR test as the respiratory epithelial cells naturally dropped after recovery,” it said.

As for antibody testing, the committee said various antibody tests offer widely different degrees of sensitivity and specificity. Thus, researchers should pay attention to the possibility of false positives in antibody formation, it said.

Since many could show no symptoms even with the Covid-19 infection, however, health officials might use antibody testing to check asymptomatic Covid-19 infection, it added.

The central clinical committee also released clinical data of Covid-19 patients accumulated so far to advise how hospitals should manage their beds and medical resources in case a second wave of the Covid-19 outbreak occurs.

According to analysis on 1,868 Covid-19 patients registered in the Korea Centers for Disease Control and Prevention’s clinical information system, the median age of the patients was 43, and it took five days from diagnosis to hospitalization on average.

On admission, 200 patients (10.7 percent) had no symptoms, and 132 (7.1 percent) needed oxygen treatment.

On the second day of hospitalization, only 0.7 percent of 1,737 patients with mild symptoms had clinical severity worsened in the next two weeks. Nine patients needed oxygen treatment, and three needed a ventilator or extracorporeal membrane oxygenation (ECMO).

Among 96 patients who needed oxygen administration and 35 severe patients requiring a ventilator or ECMO until the second day of hospitalization, 10.4 percent and 2.9 percent, respectively, experienced more severity in the next two weeks of hospitalization. On the other hand, 74 percent and 60.1 percent had the severity eased, respectively.

“If patients with mild symptoms who don’t need oxygen administration do not experience disease progression on the third day of hospitalization or the eighth day since the first symptom, they can be observed at a non-hospital life treatment center,” the committee said.

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