If, like me, you've ever had a sandwich from a dubious deli and then been laid up for days afterwards, you know that food poisoning is no trifling matter. In the past, local authorities would only ever learn of such public health issues if they get reported to the authorities by the victim (or the victim's doctor). But that misses the many cases of less serious illnesses that don't involve a doctor or hospital, or illnesses that simply aren't reported to the authorities. Now, the City of Chicago has found a new way of identifying sources of food poisoning: by...