Is e. coli possibly a fatal disease?

Only rarely: E. Coli organisms can result in a variety of different infections. However, they are usually easily managed. However, if you look at international data, e. Coli is one of the most common causes of diarrhea disease in developing countries, and the patients (usually kids) die from dehydration as a consequence of the disease--but not from the disease per se.

Depends: E. Coli can cause a wide variety of diseases, from kidney or bladder infections to acute GI disease, to sepsis from a variety of sources. This will determine whether it is possibly fatal. Suspect you are asking about traveller's diarrhea. This is usually self-limiting, but certain strains of e. Coli can produce life-threatening disease, particularly if patients are treated with antibiotics.