Determining Causation After an E. Coli Outbreak
In a case involving lots of infected meat all from the same plant and all infected with the same pathogen cultured from the victims and known (thanks to the deployment of Koch's postulates) to cause the illness in question, well, tracing the source isn't too hard. But that's not how it usually goes.
After an outbreak and after all the food has been tossed and the food areas washed down with Clorox how could you possibly find the source? Thanks to the robust sales data kept by more and more businesses it may be possible to construct a "virtual cohort" and thereafter through the usual epidemiological techniques trace an outbreak all the way back to "cooked beef topside" at a single delicatessen. The method is discussed in "The Use of a New Virtual Cohort Study Design to Investigate an Outbreak of E. coli O157 Linked to a Supermarket Delicatessen".
