We Will Never Know What Caused the Chipotle OutbreakRia Misra2/01/16 1:00pmFiled to: food sciencechipotlee coli841EditPromoteShare to KinjaToggle Conversation toolsGo to permalinkThe CDC’s investigation of Chipotle is over and their final verdict is in: The outbreak is finished, but the agency has no idea what caused it.AdvertisementSo...what exactly does that mean?The CDC shut down the investigation early this afternoon, saying that it had been two months since the last confirmed case of E. Coli linked to Chipotle and the outbreak appeared to be over. What the news didn’t come with was any determination of what was behind the outbreak. Investigators still believe it came down to a single ingredient, but what that ingredient was remains a mystery—one the CDC doesn’t expect to be solved.AdvertisementSo how do you close an investigation without knowing what happened?Essentially, there are a couple different an investigation like this one can end. The most satisfying way is, of course, to find the cause. But sometimes, when no cause is found, an investigation can end when the outbreak has.In this case—despite genome sequencing of the bacteria, data analysis, and frequent kitchen testing—the contaminated ingredient remained elusive. Although that may seem alarming, not knowing the cause in food-borne outbreaks is actually quite common, and there are some good reasons why, according to Michael Doyle, a professor of food microbiology at the University of Georgia.