There's been growing concern that patients who previously tested positive for COVID-19 and eventually recovered could actually 'relapse' or also be 'reinfected' for the virus, after prior reports out of China suggested this could be possible.

Disease experts have speculated over the nightmare possibility, but now the World Health Organization (WHO) is looking into nearly one hundred cases in South Korea which may be instances of just this feared scenario.

"South Korean officials on Friday reported 91 patients thought cleared of the new coronavirus had tested positive again," Reuters reports. "Jeong Eun-kyeong, director of the Korea Centers for Disease Control and Prevention, told a briefing that the virus may have been reactivated rather than the patients being re-infected."

Infected person being moved from an ambulance to a hospital in Seoul, Getty Images.

The practice of health officials internationally, based on WHO guidelines, is that a patient can be discharged from the hospital and is considered free of the virus after testing negative twice. The tests must be administered at least 24 hours apart.

“We are aware of these reports of individuals who have tested negative for COVID-19 using PCR (polymerase chain reaction) testing and then after some days testing positive again,” a WHO official said from Geneva regarding the South Korea cases.

“We are closely liaising with our clinical experts and working hard to get more information on those individual cases. It is important to make sure that when samples are collected for testing on suspected patients, procedures are followed properly,” the statement said.

As global cases are now passed 1.7 million, with most concentrated in the United States, which over the weekend surpassed Italy for the first time in deaths from the disease - at over 20,600 - the possibility of the virus being "reactivated" in people would be an extremely worrisome scenario, also as world leaders look to open economies back up again based at least in part on the hoped-for assurance that already infected people would not get it again.