In the past weeks, we have seen outbreaks of Salmonella in sprouts and lettuce, E. coli O145 in lettuce, E. coli O157:H7 in raw milk, Salmonella in raw milk, and campylobacter in raw milk.  Still, as Lynn Terry wrote Friday in the Oregonian, many severe food poisoning incidents are never connected with their source. 

Terry reported on the Valenzuela family, whose young son suffered a severe E. coli O157:H7 infection:

Stephen and Sarah Valenzuela….described how their son Jet  fell violently ill when he was 3. He was hospitalized on and off for nine months. He suffered acute renal failure, was in a medically induced coma for a week, underwent dialysis and four surgeries. He almost died two times.

"We’re just lucky we got him back," said Sarah Valenzuela. Health officials never found the food that sickened him.

It is likely that the majority of food poisoning incidents are never conclusively tied to their sources.   In addition, even in reported outbreaks, the number of recognized cases is likely only a fraction of the actual illnesses.  In fact, in reference to Salmonella, the CDC has previously estimated that there are 38.6 illnesses for each confirmed case in an outbreak.