Fatigue is an unspecific symptom caused by a systemic body response to the infection. Sometimes, dehydration is the primary cause, while in other cases, it can be due to high fever or some other health issue in a patient with E. Coli infection. Whatever the case may be, patients describe feeling drained, without motivation to do anything. As soon as the patient recovers, with rest and proper nutrition, fatigue fades away. The elderly are more prone to suffer from fatigue.