Well thank you for clarifying the level of understanding I’m dealing with...I’ll dumb my comments down for you: 1) it isn’t LIKELY, it is POSSIBLE. The one sure way we have to make sure it doesn’t happen is immunization: no replication=no mutation 2. Viruses are not symbiotic, this explains why they jump hosts. If way down deep in their little virus brains they thought “hmm, if I start killing my host, I will die too, so I better become less lethal”, then they wouldn’t jump to human beings from monkeys or birds.

All viruses are obligate parasites; that is, they lack metabolic machinery of their own to generate energy or to synthesize proteins, so they depend on host cells to carry out these vital functions. Feel free to use the Google machine if you’d like to further continue this conversation. I’d go on, but I’m out of crayons and sock puppets.