Covid-19: What is a virus?

I have been reading The Great Influenza by historian John M. Barry, a fascinating book about the 1918 pandemic. It is a combination of history and personalities (for example, those who contributed to the professional-ization of medicine and medical research in this country, which happened surprisingly recently, at the end of the 19th century), science and biology. I find the former more accessible: I am a social scientist, after all. My father, an organic chemist, convinced me early on that I would never understand science. (That's my story anyway, and I'm sticking to it.)

Today  I hit a rather detailed explanation about viruses and how they physically work. Some of it was quite straightforward:

The virus itself is nothing more than a membrane—a sort of envelope—that contains the genome, the genes that define what the virus is. It is usually spherical (it can take other shapes), about 1/10,000 of a millimeter in diameter, and it looks something like a dandelion with a forest of two different-shaped protuberances—one roughly like a spike, the other roughly like a tree—jutting out from the surface.
 These protuberances provide the virus with its actual mechanism of attack. That attack, and the defensive war the body wages, is typical of how shape and form determine outcomes.

So far, so good. Earlier, the author explained that business about "shape and form" in terms of fitting round pegs into round holes of various tightnesses, or, of course, into square holes (i.e., no fit). In other words, the "spikes" and "trees" need to find "receptors" that will accept their shape exactly. But then he started throwing big words around: hemagglutinin, sialic acid, vescicle, neuraminidase. And I was lost.

He also mentioned RNA viruses vs. DNA viruses. Covid-19 is an RNA virus; specifically, it's a coronavirus (CoV). Other RNA viruses include influenza and HIV. What differentiates them, I wondered?

Then again, first things first: just what is a coronavirus?

I started to dig around, and found a decent enough page at the Merck Manual website, "Coronaviruses and Acute Respiratory Syndromes (COVID-19, MERS, and SARS)." It explains that there are numerous coronaviruses, first discovered in the 1930s in poultry, but that only seven affect humans: four of them are responsible for symptoms associated with the common cold; the other three are Middle East Respiratory Syndrome, Severe Acute RS, and Covid-19, aka SARS CoV-2. (So until recently, there were only six.) The website has a very cool 3D graphic, with the following caption: "This model depicts ultrastructure of the SARS-CoV-2 coronavirus. A positive-sense single-stranded RNA virus (+ssRNA), its RNA functions as both mRNA and genomic RNA (gRNA). Internally, helical gRNA is enveloped by N protein, forming the nucleocapsid. On the surface, spike glycoproteins mediate infection by binding to angiotensin-converting enzyme 2 (ACE2) receptors on lung, intestine, kidney, and blood vessel epithelium." Exactly the sort of language that causes my eyes to glaze over.

I know this is complicated, and very difficult to explain to a lay audience—especially someone like me who really wants to understand but simply doesn't have the necessary background in science and biology and chemistry and genetics and . . . well, you name it.

Which reminded me: maybe the first question to tackle here is, Just what is a virus?

So I thought I'd see if there were any good YouTube explanations of all this. And I found a few, some about viruses generally, a couple about Covid-19. Maybe if I watch them all enough times, I'll wrap my head around what all this is that's afflicting the world right now. I hereby share them with you.

First up, let's just watch a virus particle attach to a lung cell—the beginning of infection:

Now, "What is a virus? How do viruses work?," made in 2015.

The next two are about SARS CoV-2/Covid-19 specifically, posted in March of this year:

This next one, made in 2018 and again about viruses generally, is from PBS, who include a note: "Hi all. YouTube appears to be recommending this video due to the 2020 coronavirus outbreak. For reliable information regarding this outbreak, we recommend you visit the Center for Disease Control's website." 

Finally, here's "Professor Dave" from 2017 with "Viruses: Molecular Hijackers":

I could go on. There are lots of good resources out there. Now I need to sit and watch these. And see what I can learn. (And then, step two: see if I can find any videos describing the difference between influenza and coronavirus, to understand better—though I certainly believe it—just why this pandemic "isn't just another flu.")

Meanwhile, here in Monterey County, the total count of confirmed cases ticked up one more, to 64; deaths still at 2.

Stay inside. Stay safe. Stay healthy.