One and a half months after the Chipotle E. coli outbreak began, the food source remains a mystery. Although this is the case for the majority of food poisoning outbreaks, it seems strange in this case for a number of reasons, not the least of which is that despite the company’s extraordinary efforts to eliminate the problem, new cases – and cases in new states, were reported this week.
The outbreak now includes 52 people in nine states. Since the last update, on November 20, the outbreak has expanded to include seven new illnesses and three additional states: Illinois, Maryland, and Pennsylvania.
Why is this strange?
When the outbreak was first detected by Washington State health officials in late October, they believed it affected only Chipotle locations in Washington and Oregon. Five days later, when the Centers for Disease Control and Prevention (CDC) made its initial announcement on November 4, the outbreak included 39 cases in those states and Chipotle had voluntarily closed 43 locations in Washington and Oregon, even though the illnesses were associated with 11 locations.
Using genomic testing, health officials identified the outbreak strain of E. coli O26. All samples from case patients in Washington and Oregon matched this strain. Health officials scanned the PulseNet database, for matches of this strain reported elsewhere. Two days later, November 6, they found one. In Minnesota.
The Minnesota case had not eaten at a Chipotle before becoming ill. So, for weeks, despite the DNA match, health officials said the case did not appear to be related to the outbreak in Washington and Oregon which was reported as a two-state outbreak.
On November 10, Chipotle announced it would begin reopening all of its Washington and Oregon locations. They had all been deep-cleaned, sanitized and supplied with all new ingredients. All fresh produce, raw meat, and dairy items were tested for pathogens prior to restocking restaurants.
The company also said tests of all employees in Washington and Oregon were negative for E. coli, an indicator that food was contaminated before it entered the restaurants. Also negative for E. coli were the results of 900 tests on samples from restaurant equipment and surfaces.
Then, on November 20, health investigators decided that DNA doesn’t lie and included the Minnesota case along with another case from that state and cases from California, New York and Ohio. A six-state outbreak. The state-by-state breakdown of the 45 cases reported by the CDC on November 20 was: California (2), Minnesota (2), New York (1), Ohio (1), Oregon (13), and Washington (26).
Of the 45 cases reported from six states on November 20, all but two reported eating at Chipotle before they became ill. So, the Minnesota case plus one other. What did they eat before they became ill?
In its November 17 update, the CDC said, “Additional illnesses are under investigation by Washington and Oregon and will be reported if they are confirmed to be infected with the outbreak strain of STEC O26. There have been no reported infections with the outbreak strain of STEC O26 in Washington or Oregon since the Chipotle Mexican Grill locations closed in the Pacific Northwest on October 30, 2015.”
It’s likely that two of the “additional illnesses under investigation” occurring before October 30 were confirmed, as Washington’s total increased by two cases. The other six were from four states as follows: California (2), Minnesota (2), New York (1), Ohio (1).
Of those six cases, one of which had previously been identified but excluded from the case count as the patient did not eat at a Chipotle before becoming ill, three occurred after October 30- two on October 31 and one on November 8.
That means two of the cases occurred before October 30. Why weren’t they counted earlier? Were the states where they occurred late in uploading them to the PulseNet?
It also means that whichever food item that is the source of the outbreak was more widely distributed than previously thought and therefore not eliminated from the supply chain with the company’s new companywide safety measures or its extensive efforts in Washington and Oregon.
By this time, November 20, results from 2,500 tests on Chipotle’s food, restaurant surfaces, and equipment were in and none was positive for E. coli, according to the U.S. Food and Drug Administration.
On December, the CDC again issued an update on the investigation. Seven new illnesses from six states have been reported. Two of them started in October, five began in November.
Why are cases that began in October just being reported now?
Of the newly reported November cases (November 4, 8, 10, 11 and 13) the case patients who became ill on the 11th and 13th did not eat at Chipotle. Where did they eat? And what do those places have in common with Chipotle?
But also, and maybe more importantly, in which states did the three November cases who did eat at Chipotle take place? The case count in Oregon has held steady at 13 for several weeks and increased by just one in Washington since the November 20 update. That location or locations must have some kind of supply in common with Washington and Oregon. It’s strange and worrisome that the connection remains a mystery.