An illness that is able to cause death.
illness
She died from a unknown illness
How about poisons
Aristotle died from an unidentified stomach illness.
microorganisms in it that can cause illness, diseases, and death.
She died from a unknown illness
Not in humans.
Hamlisch died after a brief illness. Details of his death are not being released.
tetanus
It can cause illness, injuries, disabilities or death.
A terminal illness is one that cannot be cured or effectively treated and carries a likely prognosis of death. Mental illnesses would not be considered terminal as they are not physical in nature, and therefor not cause death by one simply having the illness.