Covid-19: What is coronavirus?

Structure of a severe acute respiratory
syndrom–related coronavirus
virion

The other day I started exploring the question of coronavirus, but deflected into a more elementary look at viruses in general: what they are, how they work. Today I'm back to the original question, because unlike certain other flus we've been hit by in the past—e.g., the "Spanish" flu, H1N1 (1918); the Asian flu, H2N2 (1957); the Hong Kong flu, H3N2 (1968); or the swine flu, H1N1 again! (1999), coronavirus is never described with those Hs and Ns—which stand for the glycoprotein hemagglutinin and the enzyme neuraminidase, the molecules that stud a virus particle and allow attachment to "receptors" on cells. (The numbers describe the specific shapes of those molecules.) Nor are SARS and MERS, two other coronaviruses. Instead they have (if I'm understanding correctly) less specific "spike" glycoproteins—which is what makes them a lot harder to analyze and find a vaccine for. (Remember: four coronaviruses are responsible for the common cold, and there's no vaccine for that. Then again, the common cold doesn't kill.)

In my research (i.e., googling), I found a few interesting (and readable, written for laypeople) articles that address the novel coronavirus we are dealing with, SARS CoV-2. Rather than try to summarize them, I'll clip a couple of quotes and provide links. They do make for fascinating reading, as I, nonscientist that I am, try to make sense of this submicroscopic and potentially deadly world.

3D atomic scale map of the
SARS CoV-2 protein spike
which the virus uses to
invade human cells

First, in February, the coronavirus "spike" protein's genome was mapped, opening the way for a vaccine. As one of the researchers in question, Jason McLellan, explained:

Though the coronavirus uses many different proteins to replicate and invade cells, the spike protein is the major surface protein that it uses to bind to a receptor—another protein that acts like a doorway into a human cell. After the spike protein binds to the human cell receptor, the viral membrane fuses with the human cell membrane, allowing the genome of the virus to enter human cells and begin infection. So if you can prevent attachment and fusion, you will prevent entry. But to target this protein, you need to know what it looks like.

Hence: genome mapping.

Speaking of vaccines, here is an overview of "everything you need to know" about a coronavirus vaccine (maybe), and an article from Johns Hopkins on research being conducted there (both from March).

Then, responding to rumors that SARS CoV-2 might have been engineered in a lab in Wuhan, is "The Coronavirus Was Not Engineered in a Lab. Here's How We Know" by Jeanna Brynner. Here, researcher Kristian Andersen explained about looking

at the genetic template for the spike proteins that protrude from the surface of the virus. The coronavirus uses these spikes to grab the outer walls of its host's cells and then enter those cells. The [researchers] specifically looked at the gene sequences responsible for two key features of these spike proteins: the grabber, called the receptor-binding domain, that hooks onto host cells; and the so-called cleavage site that allows the virus to open and enter those cells.
 That analysis showed that the "hook" part of the spike had evolved to target a receptor on the outside of human cells called ACE2 [angiotensin-converting enzyme 2], which is involved in blood pressure regulation. It is so effective at attaching to human cells that the researchers said the spike proteins were the result of natural selection and not genetic engineering.

 In the above image, the ACE2 binding domain is green.

This is all heady, complicated stuff, and I suppose I could go on and on. But I'll stop there. Except I did find another YouTube video! Here you go: Pharmacology—Coronavirus Made Easy! It explains the spikes! And more.

Today's count for Monterey County: 136, up 17 from a couple of days ago; still only 3 deaths—whose ages, I learned today, were 97, 92, and 93.

Stay inside. Stay informed. Stay healthy.

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A couple of weeks later I found this excellent article: "Coronaviruses: A Brief History." So I am filing it here.