>>17785920
>The original strain can somehow get replaced by a newer strain?
the original strain BECOMES the newer strain by mutation, because a single strand RNA virus does NOT have a mechanism to ensure that it's copied correctly. so mutations occur often, virtually every time it's passed from one host to another. furthermore, it's why epidemics (real ones) eventually disappear on their own (bubonic plague, black death, etc). if the mutation is more deadly, the host dies before it gets passed on. if it is less deadly, it is therefore more contagious, and naturally immunizes "the herd" by infecting them.
try reading a few books, then come back. you got lucky tonite, but in general, this is NOT the place to come for a general science education.