Focus: GS-III Science and Technology
Ever since cases of ‘reinfection’ — people who had tested negative for COVID-19 testing positive again after a while — emerged the question of latency of the SARS-CoV-2 virus is being hotly debated.
What is a latent viral infection?
- A latent viral infection is an infection that is inactive or dormant and does not replicate within the host.
- It however possesses the capacity to be reactivated at some point, causing a flare-up of the disease much later.
- As opposed to active infections, where a virus is actively replicating and potentially causing symptoms, latent (or persistent; but not chronic) 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.
- Latent viral infections can be reactivated into a lytic form (the replication of a viral genome).
- The ability to move back and forth from latent to lytic infections helps the virus spread from infected individuals to uninfected individuals.
Chronic and Acute
- Viruses fall into two broad categories: chronic and acute; while a chronic virus will infect its host for extended periods of time, often through the lifetime of the host.
- An acute infecting virus, such as influenza and rotavirus, is cleared from the body after a few days or weeks.
- The ability of chronic virus to enter the latent stage and reactivate into the lytic stage could be a strategy to promote its survival.
Does SARS-CoV-2 go into latency?
- None of the observations conclusively proves 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.
- 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 are expected to occur.
- It’s entirely possible to have detectable, then non-detectable, and then detectable SARS-CoV-2 virus because of the limit of detection of our current testing.
-Source: The Hindu