Poor immunity or mutations? South Korea investigates ‘shrewd’ coronavirus as reinfections creep up

141 South Koreans have retested positive for Covid-19. While it’s a small fraction of recovered patients, it raises doubts about developing a vaccine

Health experts say this could be from reinfection, reactivation after being dormant, or simply mass testing picking up remnants of the virus in patients

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Health care workers arrive for duty at Dongsan Medical Centre in Daegu, South Korea. The city has seen a number of cases of recovered coronavirus patients testing positive again. Photo: AP

Published: 5:31pm, 16 Apr 2020Updated: 7:07am, 17 Apr 2020

In late February, South Korean health officials on the front lines of the battle against the novel coronavirus noticed a strange phenomenon. After contracting and recovering from the virus, a patient tested positive for a second time.

Within weeks, the number of patients testing positive twice rose steadily and the trend became clear.

By Thursday, at least 141 people in South Korea had retested positive for the virus officially called SARS-CoV-2, according to the Korea Centres for Disease Control and Prevention, most of them in Daegu and North Gyeongsang Province, the original centre of the country’s outbreak. Fifty-five of the cases were people in their 20s or 30s.

A health care worker wearing protective clothing takes a test sample for the Covid-19 coronavirus in South Korea. Photo: AFP

“In the case of Sars and Mers, we did not see people testing positive again after full recovery,” KCDC Deputy Director Kwon Jun-wook said on Thursday, referring to severe acute respiratory syndrome and Middle East respiratory syndrome. “This novel coronavirus appears to be very evil and shrewd.”

While accounting for only a small fraction of the more than 7,500 discharged patients in the country, the phenomenon has raised important questions for public health officials around the world who are struggling to understand the virus behind the respiratory disease Covid-19, which has claimed over 130,000 lives and halted commerce and travel worldwide.

The rising number of such cases in South Korea – more than half of them people in their 50s or younger – comes as authorities look to loosen guidelines on social distancing after bringing the number of new infections down from hundreds to about two dozen each day.

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