Hemolytic-uremic syndrome (or haemolytic-uraemic syndrome), abbreviated HUS, is a disease characterized by hemolytic anemia (anemia caused by destruction of red blood cells), acute kidney failure (uremia), and a low platelet count (thrombocytopenia). It predominantly, but not exclusively, affects children. Most cases are preceded by an episode of infectious, sometimes bloody, diarrhea acquired as a foodborne illness or from a contaminated water supply and caused by E. coli O157:H7, although Shigella, Campylobacter and a variety of viruses have also been implicated. It is now the most common cause of acquired acute renal failure in childhood. It is a medical emergency and carries a 5–10% mortality rate; of the remainder, the majority recover without major consequences but a small proportion develop chronic kidney disease, meaning at some point they will likely become reliant on renal replacement therapy (dialysis or transplantation). The primary target appears to be the vascular endothelial cell. This may explain the pathogenesis of HUS, in which a characteristic renal lesion is capillary microangiopathy.