COVID-19: THE NOVEL DISEASE

So what is this COVID-19? What’s with the little giant’s name on the lips of just about everyone? It has become quite a famous fellow. Pardon, infamous fellow.

Quickly, let’s run through some?facts, things I am certain you have come across with the vast number of videos, news, pdfs and whatever one can think of flying all over the internet. We should give thumbs-up to the scientists working out there on this, for the data accumulated already considering the short period of time.

Before going any further, please note the essence of this article: It is to explain briefly and in the simplest terms as possible the mechanism (or you could call it science) of the virus. I am going to be writing here for the fun of it. NOT to blow an already inflated situation. This is also to create a kind of awareness –in the science-kind of way.

First, let’s start with those facts:

?CO is for Corona, VI for virus and D for disease. 19 is for 2019, the year it broke out in Eastern China –Wuhan, Hubei Province.

So, can we say COVID-19 is an acronym?

?Reports of this case was first heard (as we were told) by World Health Organization, WHO on the 31st of December, 2019. The previously unknown virus was reported as the cause behind a number of pneumonia cases.

?COVID-19 was the official name given by WHO on 11th of February 2020.

?The virus that causes the disease, severe acute respiratory syndrome coronavirus 2, SARS-CoV-2, was also officially named on this same date by the International Committee on Taxonomy of Viruses (ICTV).

The virus, though genetically related to SARS-CoV responsible for the epidemic in 2002/2003 which started from Guangdong Province, China, is quite different. I mean, the two viruses are not the same hence the 2 at the back of the name.

?Did you notice that the disease and the virus have different names? SARS-CoV-2 is the virus causing the respiratory disease, COVID-19.

?Did you also notice the naming by different official bodies?

?The coronavirus was initially called 2019-nCoV or Wuhan coronavirus before the now-standard SARS-CoV-2.

?Covid-19 was first designated a Public Health Emergency of International Concern (PHEIC) in 30th of January, 2020 by WHO out of reluctance to call it a pandemic. But this changed on March 11 as Covid-19 was declared a pandemic. Declaring a pandemic creates fear worldwide, and this, WHO wanted to avoid.

Now though…

?Human coronaviruses have been identified since the 1960s. SARS-CoV-2 is just one among others.

Plenty more facts can be added to these but then this isn’t what ‘this’ is about, so let’s move.

? ON NOMENCLATURE:

Order; Nidovirales

Family; Coronaviridae

Subfamily; Orthocoronavirinae.

Genera; Alphacoronavirus, Betacoronavirus, Gammacoronavirus, Deltacoronavirus.

Coronaviruses are a class of viruses. Seven have been identified as human-infecting. These are; 229E, OC43, SARS CoV, HC NL63, HKU-1, MERS-CoV and now this SARS-CoV-2. Only the alphacoronavirus and betacoronavirus have been known to infect humans so far. SARS-CoV-2 is a betacoronavirus.

I loved all of my Essential Biology textbook except this aspect above so I will understand if you hardly glanced at it. Again, it’s not actually what I am about.

?What exactly is a?VIRUS?

Virus is sometimes said to be at the edge of life. It is a nonliving organism that becomes living the moment it comes into a living system; They can’t carry out the things living things do on their own until they get an host and BOOM! they are alive. They start to grow i.e replicate using the machineries of this host.

THE STRUCTURE?of a virus which is a vital matter for attachment and entry into a cell is relatively very simple, consisting of a nucleic material (DNA or RNA) and a protein coat called Capsid. Some have an extra covering called envelope and some such as the bacteriophage (the virus that eats bacteria) have extra appendages such as tail fibers. But basically, viruses contain a genomic material enclosed in capsid –a nucleocapsid.

SARS-CoV-2 is not different: they have a?positive single stranded RNA?enclosed in a capsid and three main surface proteins enclosing this nucleocapsid. These are the envelope, the hemagglutinin esterase (HEs) and the spike proteins, all embedded in a lipid bilayer. The spike proteins are responsible for the crown-like projections and for attachment to a receptor on the surface of a cell. The spikes earn the virus the corona in its name, the Latin word for crown.

?MECHANISM

The droplets from a person already infected with SARS-CoV-2 is …very bad. The virus which can last for about three hours in the air and three days on a steel surface is transmissible. Touching contaminated areas with your hands and placing those same hands in the mouth or nose grants the access the virus needs into the body.

One good place for the virus to start on entry into the body is the alveoli of the lungs. The spikes of the virus stick to a receptor called ACE2 found on the surface of our cells. Aside from the lungs this receptor is also located in the membrane of the blood vessels, the heart and even the kidney. The higher affinity of this new strain of virus for the receptor is one of the factors that endow it with its peculiarities –naturally, the tighter the binding, the lesser viral cells required to mount an attack.

The spike is split to two structurally and is opened up by cell proteases. The opening of the spike allows the entry of the virus into the cell (via a receptor-mediated endocytosis) and also releases the genomic material into the cytoplasm of the cell.

Above shows the gene structure of the SARS-CoV virus and the MERS-CoV (Middle Eastern Respiratory Syndrome).

From the diagram above, you see the binding. After this binding there is an uncoating which releases the genome {+ssRNA strand} into the cytoplasm. The positive single stranded RNA serves as the template {sense strand} read by the ribosome of the host cell.

The adjective, positive, in front of the RNA is because it can be read directly (by ribosome) to produce proteins. This 5’-capped-3′-Poly-A-tailed mRNA also encodes for non-structural proteins (NSP) –ORF 1a and ORF Ib, these actually takes about two-third of the gene structure.

{To recap, the RNA found in the virus is read by ribosomes to give two proteins {enzymes} replicase and transcriptase}.

Do follow the diagram. The two arrow to your far right, shows the translation (the reading of ORF 1a and ORF 1ab by ribosomes) to produce two proteins known as polyprotein 1a (pp1a) and polyprotein 1ab (pp1ab). These proteins get proteolyzed to smaller fragments yielding replicase and transcriptase. Both of these combine to form a complex known as the replicase-transcriptase complex.

Next, the complex binds to our RNA strand (still the old guy, the same positive strand) and begins the process of replication.

Replication is carried out by RNA-dependent RNA polymerase and gives a RNA product but of opposite sequence, an anti-sense strand also called negative single stranded RNA {-ssRNA} which serves quite a need in the whole process.

Two?things happen; the replicate product can be replicated again, producing +ssRNA (which makes sense right? A sense strand will give an antisense strand and vise versa when replicated). The newly synthesized +ssRNAs serve as new genomic products of the about to be packaged new unfriendly viral cells.

Discontinuous transcription?of the antisense strand is the other event that happens. Look at that down arrow with transcription written beside it; the antisense strand is transcribed discontinuously to yield what is known as subgenomic mRNAs that code for structural proteins such as spike, envelope, membrane and nucleocapsid proteins. The word subgenomic mRNA is because they are all synthesized from the transcription of one (antisense) strand discontinuously.

Translation then occurs again, but these time involving the subgenomic mRNAs. This occurs on the surface of the?rough?endoplasmic reticulum, RER.

So far, new +ssRNAs and new proteins have been synthesized. These (RNA and protein) are sent to the Golgi bodies for packaging. The Golgi bodies after packaging transports them to the surface of the cell membrane via vesicles and release the viral cells.

The released virions move to attack the next cell and start the cycle all over again. This continues and soon the number of dead cells accumulate.

Of course, the immune system soon kicks into gear to fight against these intrusions. But one thing is the virus already has a headway, and since it replicates very fast, the body’s defense (immune cells) are given quite a work to do. Some of the symptoms seen at the early stage of these infection is due to the immune system doing its work; the increase in body temperature helps the immune cells function better and at the same time creates a kind of hostile environment for the virus, weakness is due to the extra burden placed on the body and bone ache from the extra need and production of white blood cells.

A very healthy immune system can fight and win this battle. The danger lies for those with compromised immune system such as the elderly or those with a condition that already has their immune system weakened.

So there is this hypothesis I saw somewhere. It sounds very logical so I am going to note it down here. It said the reason the symptoms of the disease are slow in manifestation is due to the mechanism of action of the coronavirus. Viruses that attack the lungs can attack either the upper respiratory area or the lower respiratory area. The attack on the former spreads fast but has mild consequences compared to an attack on the later which is quite severe. The SARS-CoV-2 attacks both areas; the upper respiratory area first and hence the casual symptoms (Headaches, running nose, coughing, dizziness, and sore throat) seen in the first few days. These conditions are like the normal little complex things we go through every day, at least until the attack gets to the lower parts. At this stage, a lot of lungs cells have been destroyed. And the dead cells along with fluids accumulate. These two things cause the depletion of oxygen. Do remember that that’s just one hypothesis trying to reason out the reason for the length of time taken to notice the infection in a person.

Quite a number of things are yet to be clarified/clearly understood about this novel virus.

But one thing is sure and certain, oxygen distribution is tampered with and not by a little extent.

And the immune system gets weakened, exposing it to attack from other microbes such as bacteria and these complicates things, again, not by a little extent.

Someone also said this coronavirus should remember the ‘Ladies First’ thing. Funny. But it has been discovered that men get killed by the virus more than women. The reason for this is not yet certain.

#Anyone, male or female, old or young, can get infected.

Here, I am rounding up.

Let’s pray for our world; for the consolation of those that have lost their loved ones to this and for the?stop of the spread.

Let’s do the things we can do to keep ourselves safe.

Social/physical-distancing is one best strategy you should employ strictly.

Finally, you are asked to wash your hands properly (for 20 seconds) with soap and under running water to be safe. A simple practice but very effective. The soap molecules ripple/tear apart the lipid shell, spilling out the ‘innards’ and hence destroying the virus.

Don’t forget to wash your hands.

Sanitizer with about 60% alcohol is good but then the dead particles still remain on your hands. This makes washing better. Everything gets rinsed off.

Do take care of you. And have a corona-free holiday.

Glory.