CDC is collaborating with public health officials in several states and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) to investigate a multistate outbreak of Salmonella Typhimurium infections linked to eating ground beef purchased from Hannaford Supermarkets. Representatives from Hannaford have been cooperating with public health officials throughout the investigation. Public health investigators are using DNA “fingerprints” of Salmonella bacteria obtained through diagnostic testing with pulsed-field gel electrophoresis (PFGE) to identify cases of illness that may be part of this outbreak.