A cluster of Salmonella Typhimurium DT104 cases was found in the northeastern United States in late 2003. The strain was resistant to several antibiotics and was referred to as R-type ACSSuT. Illness was associated with consuming grocery store bought ground beef that was prepared at home as hamburgers. Product traceback linked the cases to a single, large ground beef manufacturer that had previously been implicated in a multistate outbreak of a highly antibiotic resistant strain of Salmonella Newport in 2002. The meat processor produced much of the ground beef from culled cows. On January 29, 2004, the USDA issued a reminder to consumers to cook beef thoroughly, but no product recall was issued. Related cases were found through April, 2004. Cases were more likely than controls to have pre-existing medical problems.