Persistent reports have suggested that some patients who have recovered from the novel coronavirus have relapsed, but a South Korean study suggests this is not the case.
Scientists investigated after 277 patients in the country were reported as having fallen ill or tested positive a second time.
But the researchers said that reports of relapses were due to testing failures, with the tests used having detected traces of dead virus, not signs of infection.
Dr Oh Myoung-don, of Seoul National University, said: “The tests detected the ribonucleic acid of the dead virus.”
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Oh told the Korea Herald that the polymerase chain reaction tests used in South Korea can detect fragments of dead virus cells that can take months to clear.
He said: “PCR testing that amplifies genetics of the virus is used in Korea to test COVID-19, and relapse cases are due to technical limits of the PCR testing.”
A World Health Organization (WHO) expert said this weekend that positive tests did not mean that patients were reinfected.
Dr Maria Van Kerkhove said that patients were testing positive after dead virus cells came out during the healing process.
She told the Andrew Marr Show: “Some individuals are finding they test negative after a week or two or longer, are finding that they are testing positive again.”
She added: “It is not infectious. It is not reinfection. It is not reactivation. It is actually part of the healing process that has been captured again as being positive. So that is something really interesting.”
Van Kerkhove said that it’s still not clear whether people can be reinfected with coronavirus.
“That is a very important question. When someone is infectious they develop anti-bodies and they develop part of an immune response one to two to three weeks after infection.
"Does this mean they have immunity? Does it mean they have a strong protection against reinfection and if so how long does that last?
"We do not have the answer to that yet."