An acute onset diarrhoeal illness (with or without blood or mucus in stool)
OR
Any case with Haemolytic Uraemic Syndrome (HUS) or Thrombotic Thrombocytopenic Purpura (TTP) with or without a history of an acute onset diarrhoeal illness.

Note: In the absence of HUS/TTP, asymptomatic infection or presentations with milder bowel symptoms (e.g. occasional loose stools) and/or non-diarrhoeal abdominal symptoms do not meet the case definition.