Can be. However, sepsis is usually not fatal; depending on the patient, the source and cause of infection, its susceptibility to treatment, closeness of the patient to adequate care and time to antibiotic therapies the survival of the patient varies. There are survival calculators (as morbid as that is). Here is a link to a french page that i use: http://www.Sfar.Org/article/315/scores.
Sometimes. Sepsis can be fatal, about 25-30 % of patients with this condition die. The probability of death goes up or down based on the severity of the sepsis, other medical conditions the patient may have, the cause of the sepsis and other factors.