Recovered South Korea patients test positive, suggesting coronavirus may have been 'reactivated'

South Korean officials have reported 91 patients thought cleared of the new coronavirus had tested positive again.

Jeong Eun-kyeong, director of the Korea Centers for Disease Control and Prevention (KCDC), told a briefing yesterday the virus may have been "reactivated" rather than the patients being re-infected.

South Korean health officials said it remains unclear what is behind the trend, with epidemiological investigations still under way.

The prospect of people being re-infected with the virus is of international concern, as many countries are hoping that infected populations will develop sufficient immunity to prevent a resurgence of the pandemic.

The South Korean figure had risen from 51 such cases on Monday.

Nearly 7,000 South Koreans have been reported as recovered from COVID-19, the disease caused by the new coronavirus.

"The number will only increase, 91 is just the beginning now," professor of infectious diseases at Korea University Guro Hospital Kim Woo-joo said.

The KCDC's Jeong raised the possibility that rather than patients being re-infected, the virus may have been "reactivated".

Kim also said patients had likely "relapsed" rather than been re-infected.

False test results could also be at fault, other experts said, or remnants of the virus could still be in patients' systems but not be infectious or of danger to the host or others.

"There are different interpretations and many variables," professor of pulmonary medicine at Hallym University Sacred Heart Hospital Jung Ki-suck said.

"The government needs to come up with responses for each of these variables."

South Korea on Friday reported 27 new cases, its lowest after daily cases peaked at more than 900 in late February, according to KCDC, adding the total stood at 10,450 cases.

The death toll rose by seven to 211, it said.

The city of Daegu, which endured the first large coronavirus outbreak outside of China, reported zero new cases for the first time since late February.

With at least 6,807 confirmed cases, Daegu accounts for more than half of all South Korea's total infections.

Coronavirus: what you need to know

How is coronavirus transmitted?

The human coronavirus is only spread from someone infected with COVID-19 to another. This occurs through close contact with an infected person through contaminated droplets spread by coughing or sneezing, or by contact with contaminated hands or surfaces.

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World Health Organisation and NSW Health both recommend basic hygiene practices as the best way to protect yourself from coronavirus.

Good hygiene includes:

• Clean your hands thoroughly for at least 20 seconds with soap and water, or an alcohol-based hand sanitiser;
• Cover your nose and mouth when coughing and sneezing with tissue or your elbow;
• Avoid close contact with anyone with cold or flu-like symptoms;
• Apply safe food practices; and
• Stay home if you are sick.

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Reported with AAP.