An outbreak of E. coli O157:H7 infections was associated with eating in-shell hazelnuts (also known as filberts) purchased from bulk bins in grocery stores or in a repacked form. The E. coli strains isolated from case patients, and from a consumer product sample, matched genetically. The investigation led to a common distributor, DeFranco and Sons, a California based firm. On March 4, 2011, DeFranco and Sons issued a recall of all hazelnut and mixed nut products distributed from November 2, 2010, to December 22, 2010. Only in-shell nuts were included in the recall. The nuts were shipped to stores in Minnesota, Iowa, Michigan, Montana, North Dakota, South Dakota, Wisconsin and to Canada. Based on a consumer hazelnut sample that proved to be contaminated with the outbreak strain of E. coli O157:H7, the Minnesota Department of Health traced the hazelnuts to a December 9 shipment from DeFranco and Sons. Later the states of Wisconsin and California isolated the outbreak strain of E. coli O157:H7 from mixed nut samples.