Just leave it to Mother Nature, the most prolific mass murderer planet earth has ever seen. The morbidity vs mortality rates in the two examples you cited aren’t quite up to her standards yet, but I am reasonably sure they will get there with time and transportation.
Yep.
Every one is basically waiting for the next ‘big’ thing, for the right mutation(s) and jump to a different host/speices.
It is only a matter of time.