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GS-III :

Is SARS-CoV-2 a latent virus which can recur?

  • 26 July, 2020

  • 10 Min Read

Is SARS-CoV-2 a latent virus which can recur?

Context:

  • There are doubts over second infection of COVID-19.
  • There have been repeated instances of ‘reinfection’ from COVID-19 since early January 2020.
  • Reinfection means people who had tested negative for COVID-19 test positive again after a while.

Latency:

  • The observation of re-infection of COVID-19 brings to light the possibility of SARS-CoV-2 virus having latency.
  • The COVID-19 virus may have “reactivated” in the patients rather than them becoming re-infected.
  • A latent infection is when the virus in the body is dormant and does not replicate within the host. It however possesses the capacity to be reactivated at some point, causing the disease at a later point of time.
  • As opposed to active infections, where a virus is actively replicating and potentially causing symptoms, latent infections are essentially static which last the life of the host and occur when the primary infection is not cleared by the adaptive immune response.
  • Chronic viruses can go into latency. The latent viral infections can be reactivated into the active lytic form.
  • Examples: Herpes simplex viruses type 1 and 2, HIV, Epstein-Barr virus (human herpesvirus 4), and cytomegalovirus.

Different types of viral infections:

  • A chronic virus infects its host for extended periods of time, often through the lifetime of the host.
  • An acute infecting virus, such as influenza and rotavirus creates noticeable symptoms in a short period of time and is cleared from the body after a few days or weeks.

Flaws in testing:

  • While the RT- PCR [reverse transcription/polymerase chain reaction] tests are considered to be the gold standard for testing, all tests are not 100% accurate. False positives and false negative results can occur.
  • There are limits of detection of the current testing methods employed. The concept of “limit of detection” of a virus notes that there is a threshold where a virus can be detected.
  • A negative SARS-CoV-2 test does not mean zero infection; it means no detectable infection.

Other reasons:

  • Many viruses can survive at the mucosal level in spite of immunity. A similar behaviour is possible from SARS-CoV-2.

Example: In the case of polio virus, viral shedding can continue for up to 10 weeks, in spite of very high antibody levels post the vaccination.

  • Another reason for the positive test might be due to the host harbouring an antibody-bound virus that is non-infective.
  • Even fragmented RNA particles can yield a positive result. The remaining virus fragments in humans can also lead to positives during testing.

Conclusion:

  • So far none of the observations conclusively prove a second infection. In each one of these cases, there is sufficient reason to suspect that it is one infection, with negative results in between. This necessitates a change to testing policy.
  • There is the need to globally adopt a system where clinical signs are considered sufficient to commence treatment for COVID-19, even before an RT-PCR test is done. Also, cessation of symptoms can be taken as a signal to show that a person has recovered.

Source: TH

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