Laboratory-based surveillance of salmonella isolates serotyped at four state health departments
(Illinois, Michigan, Minnesota and Wisconsin) led to the identification of multistate outbreaks
of salmonella infections during 1990 (176 cases of S. javiana) and 1993 (100 cases of S.
montevideo). Community-based case-control studies and product traceback implicated
consumption of tomatoes from a single South Carolina tomato packer (Packer A) MOR 16·0;
95% CI 2·1, 120·6; P<0·0001 in 1990 and
again in 1993 (MOR 5·7; 95% CI 1·5, 21·9;
P=0·01) as the likely vehicle. Contamination likely occurred at the packing shed, where field
grown tomatoes were dumped into a common water bath. These outbreaks represent part of a
growing trend of large geographically dispersed outbreaks caused by sporadic or low-level
contamination of widely distributed food items. Controlling contamination of agricultural
commodities that are also ready-to-eat foods, particularly fruits and vegetables, presents a
major challenge to industry, regulators and public health officials.