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Dead Coronavirus fragments lead to false positives in recovered patients

Date: 03 May 2020 Tags: Miscellaneous


In early April, South Korea announced that patients who were declared as COVID-19 recovered have once again tested positive, suggesting that it could be a case of re-infection or reactivation.



If natural infection shows only a short duration of protection, it raised concerns about the duration of protection that vaccines can offer.



  • This news caused concern as it highlighted the issue of low levels of immunity in people who have recovered and the short duration of protection offered by antibodies developed in response to the infection.

  • Researchers said that recovered persons can test positive because fragments of the disease remained in their body.

  • The committee members found little reason to believe that those cases could be COVID-19 re-infections or reactivations.

  • The RT-PCR used for testing samples amplifies the genetic material of the virus prior to testing. The molecular test cannot distinguish between dead and live genetic fragments and hence cannot make out whether the virus is alive or not.

  • There was no indication that patients who retest positive are contagious, even though about 44% of them showed mild symptoms.

  • Researchers investigated three cases from the same family where patients tested positive after recovering. But scientists were unable to grow (culture) the virus.

  • Culturing the virus is typically done for testing and producing vaccines. The inability to grow the virus in a cell culture confirmed that live virus was not present.

  • The respiratory epithelial cell has a half-life of 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.

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