a corona virus is about 30,000 base pairs long. Its doesn't have the proof reading mechanism DNA has when replicating so something like 10^6 replications are not full genomes, just RNA junk. 1 in 10^6 are full replications. How could something like that start at a single point and infect billions of people? It can't. Its fantasy.
The furin cleavage site is something like 30 base pairs (i think) and there is no way it could structurally change the whole doomed replication process of RNA.
