Is this explanation of coronavirus accurate?

Question

I have seen the following post popping up on Facebook recently:

🧐🧐🧐

Feeling confused as to why Coronavirus is a bigger deal than Seasonal flu? Here it is in a nutshell. I hope this helps. Feel free to share this to others who don’t understand...

It has to do with RNA sequencing.... I.e. genetics.

Seasonal flu is an “all human virus”. The DNA/RNA chains that make up the virus are recognized by the human immune system. This means that your body has some immunity to it before it comes around each year... you get immunity two ways...through exposure to a virus, or by getting a flu shot.

Novel viruses can come from animals.... the WHO tracks novel viruses in animals, (sometimes for years watching for mutations). Usually these viruses only transfer from animal to animal (pigs in the case of H1N1) (birds in the case of the Spanish flu). But once, one of these animal viruses mutates, and starts to transfer from animals to humans... then it’s a problem, Why? Because we have no natural or acquired immunity.. the RNA sequencing of the genes inside the virus isn’t human, and the human immune system doesn’t recognize it so, we can’t fight it off.

Now.... sometimes, the mutation only allows transfer from animal to human, for years it’s only transmission is from an infected animal to a human before it finally mutates so that it can now transfer human to human... once that happens..we have a new contagion phase. And depending on the fashion of this new mutation, thats what decides how contagious, or how deadly it’s gonna be..

H1N1 was deadly....but it did not mutate in a way that was as deadly as the Spanish flu. It’s RNA was slower to mutate and it attacked its host differently, too.

Fast forward.

Now, here comes this Coronavirus... it existed in animals only, for nobody knows how long...but one day, at an animal market, in Wuhan China, in December 2019, it mutated and made the jump from animal to people. At first, only animals could give it to a person... But here is the scary part.... in just TWO WEEKS it mutated again and gained the ability to jump from human to human. Scientists call this quick ability, “slippery”

This Coronavirus, not being in any form a “human” virus (whereas we would all have some natural or acquired immunity). Took off like a rocket. And this was because, Humans have no known immunity...doctors have no known medicines for it.

And it just so happens that this particular mutated animal virus, changed itself in such a way the way that it causes great damage to human lungs..

That’s why Coronavirus is different from seasonal flu, or H1N1 or any other type of influenza.... this one is slippery AF. And it’s a lung eater...And, it’s already mutated AGAIN, so that we now have two strains to deal with, strain s, and strain L....which makes it twice as hard to develop a vaccine.

We really have no tools in our shed, with this. History has shown that fast and immediate closings of public places has helped in the past pandemics. Philadelphia and Baltimore were reluctant to close events in 1918 and they were the hardest hit in the US during the Spanish Flu.

Factoid: Henry VIII stayed in his room and allowed no one near him, till the Sweating Sickness that plagued his time had passed...(honestly...I understand him so much better now). Just like us, he had no tools in his shed, except social isolation...

And let me end by saying....right now it’s hitting older folks harder... but this genome is so slippery...if it mutates again (and it will). Who is to say, what it will do next.

Be smart folks... acting like you’re unafraid is so not sexy right now.

#flattenthecurve. Stay home folks... and share this to those that just are not catching on. 🤓

Most of this I have no particular dispute with, but the claim

But once, one of these animal viruses mutates, and starts to transfer from animals to humans... then it’s a problem, Why? Because we have no natural or acquired immunity.. the RNA sequencing of the genes inside the virus isn’t human, and the human immune system doesn’t recognize it so, we can’t fight it off.

sounds like saying that we can only gain an immunity to a virus that has human RNA in it. It seems to me more likely that we merely don't have any existing immunity to it because it is brand new to the human immune system; now that we've seen it, we'll gain immunity to it, and who cares what RNA is inside it? (And again, my gut says that it is the human RNA that actually gives it access to infect humans and thus become prevalent enough in the body to become a valid target for the immune system). But I'm no virologist, and I'm curious what the reality is.