Identifying the contaminated food source responsible for a food poisoning outbreak isn’t always as straightforward as it seems, especially when perishable items are involved. A short shelf life means evidence often is either eaten or thrown away before an investigation even gets started. That’s the case with the Chipotle E. coli outbreak.
Health officials suspect that contaminated produce is the source of the outbreak. But it’s likely that the tainted batch was consumed before investigators gathered samples from restaurants for testing as is often the case. The first round of tests on samples taken from several Chipotle restaurants were negative for the outbreak strain E. coli O26. Other tests are pending.
It’s important to note that finding the outbreak strain in uneaten food is not a necessary component of an outbreak investigation. In fact, it doesn’t happen often. When health investigators have food histories, traceback information and epidemiologic evidence, that’s enough to determine the source of the outbreak.
Chipotle didn’t dispute that fact. The company took responsibility, apologized and is making changes to prevent future problems. But that’s not how all food producers act.
Recent examples of companies initially operating from the “it wasn’t us” stance include Andrew & Williamson (cucumbers), Foster Farms (chicken), Blue Bell, (ice cream), Aspen Foods (frozen breaded chicken), and just about every producer of unpasteurized beverages (apple juice, raw milk). But a common food source or common facility is enough to apportion blame. Here’s why.
Food histories. When 12 people get sick and the only thing all of them ate was Food A, that’s a good indication that something is wrong with Food A.
If the illness was caused by E. coli, Listeria or Salmonella bacteria, DNA tests can be performed on samples from patients. These tests identify specific fingerprints. When samples from sick consumers produce matching E. coli fingerprints, it means they were sickened by the same source. And if the only thing they all ate was Food A, again, it is a clear indication that something is wrong with Food A.
Sometimes companies implicated in outbreaks will say “you can get E coli/Listeria/Salmonella from lots of things.” That’s true. But what’s also true is that the E. coli on Food A is different, and looks different under a microscope, than the E. coli on Food B.
State and federal investigators are continuing the investigation of the outbreak which has sickened 42 people so far, 27 in Washington and 15 in Oregon. Fourteen people have been hospitalized.
In Washington, the 27 cases were reported. Tests on an additional four cases are pending. The confirmed cases were reported from the following counties: Clark (11), Cowlitz (2), Island (2), King (6), Skagit (5), and Whatcom (1). Ten of these people were hospitalized. None of them developed Hemolytic Uremic Syndrome (HUS), a complication that arises in about 15 percent of E. coli cases that causes kidney failure.
The E.coli strain in this outbreak, E. coli O26, produces shiga toxins that can cause severe, life-threatening illness which can, in some cases, be fatal. Symptoms include bloody diarrhea, abdominal cramps, fever, and vomiting. Anyone with these symptoms should see a doctor.