that contamination often occurs early in the production process at steps on the way from farm or field or fishing ground to market. Griffin's job is to look for trends in food related illness through analysis of outbreaks Her staff tries to identify the food source of an outbreak and the contaminating bacteria. To link cases together, the scientists use a powerful tool called PulseNet, a network of public health laboratories connected by computer that matches types of bacteria using o DNA 6 PulseNet allows epidemiologists? to associate an illness in Nebraska, say, with one in Texas, tying together what might otherwise appear as unrelated cases. Then the of the investigators to track down what went wrong in the food's journey to the table. This allows them to determine whether to recal a particular food or to change the process by which it's produced.