So, some of us are panicking about COVID-19, some of us are trying to downplay it. All of us, I think, are a little bit concerned.
But one thing I’ve noticed is that a lot of people don’t understand why this virus is so bad. It’s related to several cold viruses, after all. Why is it killing people? Why are we so afraid of it?
Setting aside the fact that new things are inherently scarier, there’s a reason why new or emerging viruses are a problem.
Actually, there are two reasons:
Our Immune Systems Haven’t Met it Yet
We’re in a constant arms race with pathogens. Viruses want to hijack our cellular machinery to reproduce themselves. We don’t want that happening. (Note, if I seem to be anthropomorphizing viruses, it’s a language thing).
Our primary line of defense against viruses is our immune system, specifically our T cells. These wander around in our blood and other bodily fluid looking for invaders. Think of them as our body’s mall security guards on patrol. When they see a known shoplifter, they kill it…or rather, they kill the cell the virus has infected.
(Allergies happen when our immune system mistakes something harmless for an invader, and auto-immune diseases happen when it mistakes healthy cells for one).
The problem is that our T cells can only recognize invaders they know. When they encounter a virus that they haven’t met before, they don’t immediately recognize it, and it spreads. By the time they realize there’s a problem, they have an entire gang of shoplifters.
Then our immune system goes heeelp, need to get rid of this, and goes on the attack. Thus, we get much worse symptoms than we do when the invader is recognized right away.
Our immune system can go “Oh, that looks like X” and go after a virus it hasn’t met before if it’s encountered something similar. This is how we discovered vaccination. Jenner noticed that dairy workers didn’t get smallpox very often. He discovered that they got a related virus, known as cowpox, and the two viruses were so similar in appearance to our immune system that if you had cowpox, you didn’t get smallpox. He started deliberately infecting people with cowpox, and within two years had worked out how to do it without making anyone sick. (Now we have it down).
In the case of SARS-CoV-2, the closest relatives are SARS and MERS. Which is potentially useful for drug development, not so useful for our poor immune systems.
It Hasn’t Fully Adapted to the New Host Yet
So, that’s why most new viruses are worse, but SARS-CoV-2 has something in common with H1N1, the pandemic flu from 2009: It’s zoonotic.
A zoonotic infection is one that crosses from one species to another. It’s usually used in reference to humans catching something from farm animals, but in 2017 a bunch of dogs died in North Carolina after catching equine influenza. Some human influenza viruses have also been known to infect pet cats.
A virus that jumps species isn’t quite sure what to do. It’s adapted enough to survive, but not enough. Now, here’s the thing: A truly successful virus doesn’t kill its host.
Host dies, virus dies. So as a virus adapts, more virulent strains that either kill their hosts or hospitalize them (a hospitalized host isn’t walking around infecting people) die out and strains which cause minor illness remain.
Swine flu is a good example of this. It was a pandemic in 2009, but if you got your flu shot this year (and I hope you did), it contained H1N1, the very strain that caused that pandemic. It’s better adapted, so less virulent, although being flu it’s still dangerous. (Get your flu shot).
SARS-CoV-2 is closely related to viruses found in bats and pangolins. (The reason you’ve heard arguments is because we aren’t exactly sure which virus it mutated from).
Adaptation also tends to increase transmissibility, but it does reduce virulence. That is to say, the R0 (number of people each patient infects) is likely to go up slightly but the CFR (percentage of infected people who die) will go down.
So, What Does this Mean for COVID-19?
At this point, it’s not clear exactly what will happen with this virus, but given the fact that it is already considerably more transmissible and less virulent than SARS, it’s probably with us permanently.
The good news is that it will probably reduce further in virulence and become seasonal. And we’ll have a vaccine. Depending on how the virus adapts, the vaccine may be recommended for everyone or only for high risk groups (likely meaning people 50 or older and people with certain comorbidities).
The best case scenario at this point, given it’s unlikely the initial pandemic will be controlled, is that SARS-CoV-2 rapidly reduces in virulence and becomes, well.
In the meantime, wash your hands, stop shaking hands and hugging people who aren’t in your household, and stay home as much as possible; and absolutely away from vulnerable people if you are coughing and have a fever. (Even if it’s not this, it’s probably flu, and you don’t want to spread that anyway).
Note that I’m not an epidemiologist, this is all armchair science, but it’s considered a likely scenario by experts. What you want to do is keep from getting this bug for as long as possible.