Outbreak of Escherichia coli O157:H7 in a child care center in Cook County, Illinois, with prolonged shedding and household transmission.

During the investigation of an outbreak of Escherichia coli O157:H7 in a child care center, illness logs were reviewed and parents interviewed to identify classroom and household exposures. Costs incurred by the center and the public health laboratory were estimated from self-administered questionnaires. We conclude that household transmission played a role in this outbreak and estimate the cost of investigation and intervention at over $6,000 per case.