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Last active Apr 15, 2020
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Layman's explanation of COVID19

Layman explanation of COVID-19

Pathophysiology

  1. Viruses need enter the host for reproduction i.e.:

    • a. host's cells for reproduction,
    • b. host's body for finding new cells to invade.
  2. SARS-CoV-2 enters through the (mucosa) of the

  3. SARS-CoV-19 enter the cells whose have Angiotensin converting enzyme 2 (ACE2) receptors (as its S-protein spike has affinity to that receptor) either by

  4. The created viruses (S, E, M and other proteins are sythetised, assembled) are fused to the cell membrane and the virus out into the extracellular space (by exocytose).

Classification

  • Family: Coronaviridae
  • Gender: Coronavirus (wrapped, pleomorphic)
  • Genome: linear single-stranded RNA + (+ssRNA)

Structure

  • Helical, or spherical
  • Diameter: 60-200nm. An analogy, if:
    • a cell has a size of human, then
    • a bacteria is just abt ~2cm bug's size, while
    • a virus is about a small ant size (~2mm).
  • single RNA without segmentation
  • Surface antigens are glycoproteins (S, E, M)
    • they're transmembrane (spans the entirety of the cell membrane)
    • Affinity/adhesion to the targeted cell's membrane (i.e. bind to ACE-2 membrane receptor)
    • they also try to neutralise antybodies
  • Nucleoproteins

Proteins

  • S: (receptor binding) spike protein for cell fusion.
  • E: (smal) envelope, not as abundant as S-Spike
  • M: (trans)membrane glycoprotein (matrix protein) for envelope formatino and budding.

Brief description

COVID19 is mainly targeting the avelioli's type II pneumacytes's ACE-2, as every viruses has a target specific sites on cells. Each cells are different. Viruses are not like bactaria, they need a target cells. The receptors are very different in every cells. The viruses are not swiss army knifes, they're very dump and they usually do not have multiple tools to invade a cell (it's not really the thruth but for simplicity it's enough).

Treatments

COVID19, can be cured by 2 main path:

    1. adaptive immune system i.e by T and B cells (in 4-6 weeks) and Vaccines do the same (So, when it's adopted it triggers the defencse system in 1-4 hours) and
    1. by drugs which try to suppress/inhibit the pathways what the virus uses to invade its target cell.

So, the virus enters the cells by endocytosis/fusion when the S-spike binds to the ACE-2 receptor.

When it's in the cell it releases its RNA (+ssRNA to be precise) to which the ribosomes start to creates the virus parts (poly proteins i.e. capsid, spikes, membrane etc.) i.e. translation.

These polyproteins parts are further cleaved by proteinases to further break down the final parts. Also, the RNA dependent polimerase also creates a lot of RNA from the positive-sense single stranded RNA (+ssRNA) from virus, so all the parts are done. During this the cell knows that something is not right with it and will send signals (interferons) to the outer world (extracellular space, in this example to the elvioly): "Heeeeeeey, I have issues", which triggers the dump innate immune system first (macrophage start releasing ROs Reactive Oxygen Species saying buddy you should die instead of the host).

So, how can we stop spreading the viruses. So we can inhibit (or express) some of these path. For example Quinine (Hydroxychloroquinine) has a hydroxy which is sticky, and can bind to the ACE-2 receptors, therefore the virus cannot enter the cells. Or there are different drugs (Remdesivir, Ritonavir, Tocilizimab and Cortilosterids etc) that inhibit other parts of these pathways.

Also, it's not the virus kills you but your immune system as your body will be immune suppressed, and other diseases or the destroyed alveiolis by your immune system will kill the host.

Why is the droplets are the most effective way to spread the virus? As it can goes directly to your lung with very high concentration. Much less probability (but it can happen) when you touch your noise mouth or eating something which is covered by some viruses (everything is covered by and/or contains viruses, bacteria, fungi etc).

So, virus is dump and can have different affinity to different cells' ACE2 receptors, and it does not have legs to walk down to your lung alveoli. So, higher the concentration higher the chance.

  • The death rate for influenza is around 1% while for covid is between ~0.5%-3.5%
  • The Series Interval (Si) is 5-7.5 for covid19 and 2.5 for influenza.
  • Reproductive Ratio is R0=2-3 while for influenza is around ~1.3) etc. That means, that covid19 is expponential while influenza is nearly static. E.g. for influenza it is almost 300K /w 3K death in Hungary in every year.

Also, afaik the multi organ failure (one of the deaths) is not related to the SARS-COV-2, but the cascade effects what it causes in the reperatory system.

Multi organ failures caused by the cascade initiate by the virus i.e. septic shock, SIRS (Systematic Immune Response Syndrome) etc and not the viruses, of course when the very severe immun response allow the virus to enter your body but it does not affect the kidney or the liver.

  • The SIRS would cause this, means the Creatinine and BUN in kidney would rise,
  • also the ALT AST (liver funct enzymes), CRP too.

The easiest way to decide whether the person know about it is asking them about explaining the causes and the timeline of the symptoms of COVID19 or on any other diseases. If they cannot then they do not know anything about it.

Symptoms & Deaths

  • fever
  • nonproductive cough
  • dyspnea
  • myalgia
  • fatigue
  • normal or decreased leukocyte counts
  • pneumonia
  • organ dysfunction:
    • shock,
    • ARDS
    • acute cardiac injury
    • acude kidney injury

Deaths caused by:

  • respiratory failure,
  • septic shock,
  • multiple organ dysfunction or failure
  • comorbidities

Pre-existing Condition

  • Cardiovascular disease: ~13.2%
  • Diabetes: ~9.2%
  • Chronic respiratory disease: ~8.0%
  • Hypertension: ~8.4%
  • Cancer: ~7.6%
  • No pre-existing conditions: ~0.9% i.e. 0.027% so, 1 of ~3703

References

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