Escherichia coli O104:H4 is an enteroaggregative Escherichia coli strain of the bacterium Escherichia coli, and the cause of the 2011 Escherichia coli O104:H4 outbreak. E. coli O104 is a Shiga toxin–producing E. coli (STEC).
The toxins cause illness and the associated symptoms by sticking to the intestinal cells and aggravating the cells along the intestinal wall. This, in turn, can cause bloody stools to occur. Another effect from this bacterial infection is hemolytic uremic syndrome (HUS), which is a condition characterized by destruction of red blood cells, that over a long period of time can cause kidney failure. Some common symptoms of HUS are vomiting, bloody diarrhea, and blood in the urine.