Benign?! People die from this disease. Benign has the meaning of not cancerous but still a growth. for the most part harmless. You could never describe cholora that way.
Precarious: Just carry over the ! mark. You would never describe cholora as not not in balance.
Cholera is transmittable but it is not like a plague (until it is like a plague). It does not guarantee death upon little contact. This is your second best answer.
Superfluous means not necessary. It's an extra that is not used in what you are doing. You'd never describe any deadly disease that way.
Morbid usually means a preoccupation with death. In medicine it is that which can and usually does cause death. So your best answer out of that bunch is a pestilent. <<<<<<< answer
