The 292 coronavirus patients that were said to have been reinfected were given false-positive results, according to South Korean officials. Over the past month, South Korea has seen people cleared of the virus testing positive again.
Fears were immediately raised after speculations of recovered cases being reinfected due to social interactions or that the virus had laid dormant before reactivating again. There are also suspicions that a person's immunity is short-lived after fighting off the virus. This could mean that if humans had no immunity of the virus, easing lockdowns would have been pointless because no-one would be protected from being infected again.
Faulty test kits
A senior South Korean official has stated that the sudden increase of reinfected people was due to a testing fault, and not because of a short-lived immunity in patients. The infectious disease expert revealed that dead-virus fragments can remain in the human body for months. The lingering fragments may cause a positive result, even though the patient is sick or infectious anymore.
The health authorities in South Korea have said that they recorded no new cases of coronavirus infections in the country. It was a first for South Korea, which avoided going into lockdown since its outbreak in February.
However, according to the Korea Centers for Disease Control and Prevention, there were four new imported cases. The total death toll in South Korea is 247. Although the country may look like it has everything under control, they are facing a new problem, and it is reinfections.
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The epidemiologists in Seoul tried to track down the cause of the trend that is worrying about the pubic. There were 51 patients in Daegu on April 6 who tested positive again, and 40 more cases in Seoul who they thought recovered from the disease tested positive again on April 10.
On April 27, it was reported that at least 222 people were in the reinfected category. The director of the Korea Centers for Disease Control and Prevention or KCDC, Jeong Eun-kyeong, stated in a briefing that the virus may have instead been reactivated. That means that the patient never completely fought the virus off because of a deficient immune response.
A Spatio-temporal epidemiologist at Seoul National University told Al Jazeera News that scientists dismissed the idea that it was due to a fault in testing. He said that few researchers think that this is a case of reinfection or an issue of accuracy in test kits and many are looking at this more as a virus reactivation.
There were about 20% of those known to have gotten sick of the virus again are in their 20s. Those who are in their 50s are making up the second-largest group. According to Dr. Roh Kyung-ho from the Department of Laboratory Medicine at the National Health Insurance Ilsan Hospital, instead of an error in test kits, he believes it is an issue that may be from a difference in the immune system function between individuals.
However, a clinical expert panel on April 29 concluded that recovered coronavirus patients who tested positive for the virus again did not show any signs of reactivation or reinfection, but rather, it showed false positives. Oh Myoung-don from The Central Clinical Committee for Emerging Disease Control, said that he and his colleagues do not see a reason to believe that the cases were reactivation or reinfections.
PCR testing limit
The head of The Central Clinical Committee for Emerging Disease Control said that the false positives on the patients were because of the technical limits of PCR testing. PCR testing is labeled as the gold standard because of its high accuracy levels but there are varying levels of sensitivity.
The panel noted that viral fragments of COVID-19 infection may exist in epithelial cells even after the virus is inactivated. The said cells can live up to three months and RNA virus in the cell can be detected with PCR testing one to two months after the elimination of the cell. Since the PCR tests can't distinguish whether the virus is alive or dead, it can lead to false positives.
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