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Spent the weekend learning about Covid-19. It’s such a smart virus. Unlike the HI virus which goes for CD4 white blood cells to get into the host body, Covid-19 utilizes a number of different host cells. It’s also able to avoid host defense cells till it has markedly multiplied.
By the time the host cells identifies the coronavirus, they quickly mount an immune response to fight it, this immune response results in release of cytotoxic chemicals that instead of fighting the virus end up destroying host tissues, especially as seen in the lungs.
Extensive release of this cytotoxic chemicals by the overzealous immune cells destroys lung alveoli which are important for gaseous exchange. If you can’t exchange oxygen for carbon dioxide, you won’t be able to perfuse body cells. It’s similar to drowning in a way. 
Why COVID-19 is called a systemic disease is that, it will invade any body cells that has a receptor mechanism that can identify it, like lock and key mechanism. So that’s why patients present with varying symptoms from the nose, lungs and all the way to the bowel.
“If you can’t explain it simply, you don’t understand it well enough” Albert Einstein.
