A Korean woman who had been discharged after recovering from the novel coronavirus has tested positive for the disease again, health officials said Saturday. 

Kwon Jun-wook, director of the National Institute of Health, said it was not believed to be a case of reinfection from someone else. He said the virus was thought to have been dormant in the patient, and the illness was able to recur because she was old and had a weak immune system.

“A normal person would have been able to defend the virus from invading the system again after developing immunity (against the coronavirus) but it could have difficult (for her to do this),” Kwon said at a regular briefing Saturday. “So some experts say the virus might have not been completely dead (in the patient’s system).”

The 73-year-old woman, who lives in Siheung, Gyeonggi Province, was discharged from the hospital on Feb. 22 after she developed no further symptoms and tested negative twice. She then had mild symptoms again and reported it to the community health center. She tested positive for the second time Friday afternoon.

The government is to consult with the country’s clinical committee to look into this and other similar cases around the world, he said, in order to draw quarantine measures for such cases.

There have been a number of cases of COVID-19 recurrence in China, particularly in Wuhan province where the coronavirus outbreak originated in late December.

Japanese authorities on Wednesday confirmed that a woman who works as a tour bus guide had tested positive for COVID-19 for the second time, three weeks after she was discharged from the hospital after showing signs of recovery.

As much remains unknown about the virus, there needs to be more research and data accumulated to determine the possibility of reinfection of the coronavirus.

“We need more research and study on how antibodies are formed after being infected with the virus, given the COVID-19 is a new virus,” the Korea Centers for Disease Control and Prevention director Jung Eun-kyung said at a briefing Thursday.

She also said that the accuracy of the diagnostic test, when and how the test was conducted and the severity of the patient’s symptoms also needs to be reviewed.

As of Saturday morning, South Korea confirmed 594 more cases of the novel coronavirus overnight to push up the total infections to 2,931.

By Ock Hyun-ju (laeticia.ock@heraldcorp.com)