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
Novel viruses, 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
Now.... sometimes, the mutation only allows transfer from animal to human, for years it’s only transmission is from an infected animal
H1N1 was deadly...
Fast forward.
Now, here comes this Coronavirus... it existed in animals only, for nobody knows how long...but one day, at an
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...
And it just so happens that this particular mutated animal virus, changed itself in such a way that it causes great damage to the human lungs..
That’s why Coronavirus is different from seasonal flu, or H1N1 any