[colour online]. Flowchart of guests attending a family party (n = 71) including number of cases (symptomatic guests with laboratory-confirmed STEC O104:H4 infection, n = 23) and non-cases (n = 48), and number of guests interviewed by questionnaire, that could be included in the cohort study (n = 69), with results of stool samples, northern Germany, 2011. STEC, Shiga toxin-producing Escherichia coli serotype O104:H4; HUS, haemolytic uraemic syndrome.