The Evolving SARS-CoV-2 Genome

This is a OPINION PIECE and should be interpreted with CAUTION!
The text is ‘overtly simplified’ for general audience and DOES NOT CLAIM scientific accuracy but is only intended to present easy to understand information.

first published : 20.08.2021

Other VOCs are expected in future as the virus is evolving but can we have an idea how would they be?

Although it is impossible to predict how the virus would further evolve, it is a very intriguing question and lets us think about the future. In a very simple attempt, the ‘future of pandemic‘ was discussed where it was hypothesized that the ‘reinfection’ and ‘long-COVID cases’ would determine how the pandemic would evolve, but the first part, ‘reinfection’ is actually about how the VOCs would evolve and hence can re-infect humans.

Therefore, it is important to think collectively how the virus continues to infect humans, and three basic concepts comes to mind.

As an easy way for access to further reading, the definitions below are from wikipedia.

  1. Virulence: is defined as a pathogen’s or microorganism’s ability to cause damage to a host. In other words, in case of viruses, how effectively and efficiently the virus can replicate, modify host defenses, and spread within the host.
  2. Infectivity: is defined as how frequently it spreads amongnst hosts. In other words, wheat we commonly read as ‘transmission rate’ or transmissibility.
  3. Antigenic escape: is defined as when the host’s immune system is no longer able to recognize and eliminate a pathogen such as a virus. In other words, the natural (post-SARS-CoV-2 infection) or vaccine induced immunity could not longer recognize the new and evolved SARS-CoV-2 VOCs. Also known as ‘immune evasion’

It is to be mentioned that these three factors have an interplay and one or other could be the dominating feature under different circumstances. For example, when the SARS-CoV-2 first infected humans, there was no natural or vaccine induced immunity, and hence the ‘virulence’ and ‘infectivity’ were the dominant features. With time, the mutations in the virus genome led to different VOCs which had either a higher virulence or higher infectivity (transmission rates) or both, as in the case of Alpha and Delta variants.

Now coming back to the initial question – how the virus would further evolve – now that we have over 200 Million infections and over 4.8 Billion first doses of a COVID-19 vaccine administered worldwide (as of 20.08.2021), over a third of the global population has some level of immunity against the original and evolved strains. That means, the new and evolved virus(es) would have the challenge to infect the already vaccinated humans, and hence ‘antigenic escape’ would be the most likely the dominating factor in near future. Moreover, any VOC which has the highest ‘antigenic escape’, would easily outcompete other VOCs in the vaccinated population. It is also important to consider that the SARS-CoV-2 transmission (one to another human) occurs within the first 5-6 days post infection while most symptomatic manifestions happen after 10 days of the infection, meaning VOCs with increased ‘virulence’ would keep evolving, as the disease (COVID-19) and sever outcome post-infection is not the limiting factor, instead give them an edge over other variants to infect more people. Together, higher ‘virulence’ in case of unvaccinated population and ‘antigenic escape’ (or immune evasion) in case of vaccinated population, or a comination of both would be the next generation of VOCs!

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