
Mark I. answered 04/24/19
EMT Turned Teacher
When a localized infection enters the bloodstream it becomes systemic (throughout the body): this is sepsis. On a similar note when cancer is localized it is far easier to treat. When it hits the bloodstream it can become systemic and thereby become fatal.
It is hard to treat simply because it is so widespread. The very young infants and geriatrics (the aged) are vulnerable to sepsis and the condition can be much more fatal. This is especially true for patients with compromised immune systems.
I hope that helps.
EMT guy