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A number of reported cases of coronavirus patients who relapsed after overcoming the disease were actually due to test failure, South Korean scientists say.
Researchers from the South Korean Center for Disease Control and Prevention (CDC) now say it is impossible for the COVID-19 viruses to reactivate in human bodies.
There have been more than 10,000 confirmed coronavirus cases in South Korea, with 245 deaths, a mortality rate of 2.3%, which is below the average of 3.4% as declared by the World Health Organization.
A total of 277 patients in the country are believed to have fallen ill a second time, as do patients in China and Japan.
This raised concerns that the virus might be mutating so fast that people were not necessarily immune to contracting it again.
However, genetic analysis of the virus has found no substantial change that effectively disguises it from the immune system.
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Partly as a result of these reports, the World Health Organization warned governments against using so-called “immunity passports” to allow people to go back to work simply because they have antibodies to the virus.
Immunity passports are a proposed way to allow countries to start lifting their coronavirus blocks in a specific way and resume economic activity.
They would be issued to people who have already overcome a COVID-19 infection and test positive for antibodies against the virus, based on the assumption that they are therefore immune.
In an update to its guideline, the WHO warned that “there is no evidence that people who have recovered from COVID-19 and have antibodies are protected from a second infection.”
But it was not expected that the polymerase chain reaction (PCR) test used to check blood for antigens, actual particles of the virus itself, could also have problems.
The South Korean CDC found that the test results for suspected relapse patients were false positives, and warned that the test they used was unable to distinguish between live traces of the virus and harmless dead samples that remain after patients have recovered.
The WHO also cautioned that immunity certification depended on rapidly developed tests that were verified for accuracy and reliability before being used.
“People who assume they are immune to a second infection because they have received a positive test result may ignore public health advice,” the WHO warned.
“The use of such certificates may therefore increase the risks of continuous transmission,” added his guide at the time, although this guide is currently under revision.
The CDC added that, unlike other viruses, such as HIV and chickenpox, which can penetrate the nucleus of human cells and remain dormant for years before reactivating, the coronavirus remains outside the nucleus of the host cell.
“This means that it does not cause chronic infection or recurrence,” explained Dr. Oh Myoung-don, head of the CDC committee, which means that patients are unlikely to relapse in this way.
In the future, it might be possible for the coronavirus to mutate and infect people who have previously overcome it, similar to the flu.
