The pandemic

2019 was when we first heard about Covid-19. Its 2021 and there are second and third waves destroying entire countries. I want to write a little about what’s known about the strains and mutations and the superpowers of this virus that has wreaked havoc all over the world.

Basics first. Lets see how this virus looks like and how it functions. The virus is called SARS-CoV 2. the number 2 because its a variant of the severe acute respiratory syndrome coronavirus that causes severe respiratory issues (as the name suggests, duh).

So, as we can see from the image, there are various components of this virus that are responsible for the infection. Now, viruses are weird alright, they have a fairly simple structure and no complicated organelles like other normal cells like our human cells or bacterial cells. for example, compare the virus image with this image of plant cells, animal cells and bacterial cells [2]:

Freaking complicated right? yeah lets not go into that. Coming back to the virus, these organisms basically rely on other organisms for living and reproducing because they don’t have the means of doing that on their own.

Lets go through the viral components one-by-one:

Envelope: This is a membrane that surrounds the nucleocapsid and protects it. The “membrane” is a part of this’

Nucleocapsid: The first half of the word represents the nucleic acid (the genetic material of the virus, DNA or RNA, RNA in this case. [note: viruses can have double or single strands of DNA or RNA and they can be positive or negative (variety yay!)]. SSRNA means its a “single strand RNA” virus and (+) means its positive). The second half of the word is “capsid” which basically is the layer that protects this genetic material [4].

And now the main component: the spike proteins!

Spike proteins: The viruses have different proteins in them, there are M and E proteins which assemble the new virus babies and send them out. And there are S proteins or spike proteins which as the name suggests, give the spike like appearance in the coronaviruses (like SARS CoV 2) and are basically responsible for fusing with the cell membrane and entering inside the cell [3]. The S1 and S2 have different functions. S1 is responsible for binding to the host cell receptor (the virus always needs a receptor to bind to) and S2 fuses the envelope to the membrane and aids entry.

This image below shows the basic functioning of an RNA virus:

Let me explain the image. So, the virus enters the host cell, and uses the cell’s machinery to convert its viral RNA to more RNA strands. But, the enzyme it uses (RNA polymerase), tends to make more mistakes in making the viral RNA as it is and mistakes mean “mutations”. So, the new virions (virus babies) that come out of the cell are slightly different in ways they probably are not supposed to be. It works for them but for us humans, it becomes hard to control them, understand them and make vaccines against them because they’re all a little bit different in their sequences! Hence, this SARS-CoV 2 which is unfortunately an RNA virus, has so many mutations making it hard to control the pandemic.

Now, about the variants, the CDC has divided the COVID-19 viruses into three main categories [5]:

Variant of interest (VOI): A variant with specific genetic markers that have been associated with changes to cell binding, reduced effect of antibodies generated against previous infection or vaccination, reduced efficacy of treatments, potential diagnostic impact, or predicted increase in transmissibility or disease severity [6]

Variant of concern (VOC): “A variant for which there is evidence of an increase in transmissibility, more severe disease (e.g.,  increased hospitalizations or deaths), significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatments or vaccines, or diagnostic detection failures.” CDC [6]

Variant of high consequence (VOHC): “A variant of high consequence has clear evidence that prevention measures or medical countermeasures (MCMs) have significantly reduced effectiveness relative to previously circulating variants” CDC [6]

There are still a lot of things to know about, like how are the strains different from each other, how are the strains getting mutated, can we predict the mutations or not or how many more mutations are yet to come, what kind of measures will be the most effective against these viruses.

As its a pretty new thing, all we can do is take precautions and not take these dangerous little things for granted.

References:

[1]https://www.frontiersin.org/articles/10.3389/fmicb.2020.01818/full

[2] https://www.britannica.com/science/bacteria

[3]https://www.news-medical.net/health/What-are-Spike-Proteins.aspx#:~:text=As%20compared%20to%20the%20M,protrusions%20found%20on%20their%20surface.

[4] https://www.youtube.com/watch?v=O1TetEto1Is

[5]https://www.cdc.gov/coronavirus/2019-ncov/transmission/variant.html

[6] https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/variant-surveillance/variant-info.html#:~:text=A%20variant%20of%20interest%20might,efficacy%20of%20therapeutics%20and%20whether

[7]https://www.masslive.com/coronavirus/2021/04/cdc-monitors-for-high-consequence-covid-variants-able-to-resist-treatment-vaccines.html