Malaria in a toddler can be rapidly fatal.
The disease varies from a mild condition to a rapidly fatal one with death in 4-18 days post infection.
Such infections include a form of meningitis that can be rapidly fatal.
This is known as endotoxic shock, and can be rapidly fatal.
It was a rapidly fatal cancer of the immune system, which is now known as Burkitt's lymphoma.
It is caused by Pasteurella multocida bacteria, and can be rapidly fatal.
Some of the less common diseases can be rapidly fatal if untreated.
All of these events lead to the possibility of brain herniation, which can be rapidly fatal.
The damage causes severe hemorrhaging or air embolisms, either of which can be rapidly fatal.
If a disease is rapidly fatal, the host may die before the microbe can get passed along to another host.