It is very unlikely that it would maintain that kind of case mortality rate if it made the jump.

As far as I know, the only place where human and animal laboratories are together is in Canada.

There are many other examples. West Nile virus spread from insects to humans; the avian flu we are now so worried about comes from birds. Diseases also jump to domesticated animals such as cows - the human variant of 'mad cow disease', from rodents, and from many different species.