so for investigators have not been able to trace the strain to a particular source like food and now, an expert on infectious disease and chair of the department of preventive maintenance at vanderbilt. good to see you. guest: good to be with you. shepard: we hear a lot of e. coli talk but when kids diet is serious. guest: it surely is and this is clearly an outbreak. and it is getting the full court press both from the centers for disease control and all the state health departments to fine the cause just as quickly as possible. and to cut it off so we do not get anymore cases. shepard: it is a big world across six states how do you begin the process? guest: the cdc coordinates and all the folks in the public health department in those states work together, interview the cases, interview other people who are close to them, who didn t get sick, and try to compare what it is they ate or didn t eat to give them a clue of what the source is because it