The story so far: Ever since cases of ‘reinfection’ — people who had tested negative for COVID-19 testing positive again after a while — emerged in early January, the question of latency of the SARS-CoV-2 virus is being hotly debated. The first such cases emerged in the east (China, South Korea) where scientists were puzzled over why or how individuals who had tested negative twice for the virus, had, after a few weeks or months, tested positive, the second time around albeit with milder symptoms. 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 a flare-up of the disease much later.
What is a latent viral infection?
A latent viral infection is an infection that is inactive or dormant, authors Sergey Sheleg and Alexey Vasilevsky write in an article in the Global Journal of Infectious Diseases and Clinical Research. “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,” they explain. Examples are Herpes simplex viruses type 1 and 2, varicella-zoster virus, HIV, Epstein-Barr virus (human herpesvirus 4), and cytomegalovirus. They are known to cause typical latent infections in humans, Sheleg and Vasilevsky add.
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They go on to explain that “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”.
Ryan McNamara, a research associate at the Department of Microbiology and Immunology, University of North Carolina, in a long tweet thread sought to explain the difference between the types of viral infections. Tweeting from @Ryan_Mac_Phd, he says: 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