The Centers for Disease Control and Prevention said Monday it is investigating a more recent batch of E. coli cases linked to Chipotle, and that it does not know yet if they are linked to a larger outbreak that began in October.
So far, the agency said five people have been reported sick in the new outbreak, with illnesses starting between Nov. 18 and Nov. 26. They include one person in Kansas, one in North Dakota and three in Oklahoma. All five said they ate at a Chipotle the week before they got sick.
The development is the latest bad news for Chipotle Mexican Grill Inc., which saw its sales plummet after the emergence of the larger E. coli outbreak that has sickened 53 people in nine states. The most recent illness linked to Chipotle among those cases started Nov. 10.
Each year, about 48 million people get sick from foodborne illnesses, according to the CDC.
Following the outbreak, Chipotle Mexican Grill Inc. assured customers that it would tighten its food safety standards. Spokesman Chris Arnold said in an email Monday that the chain is in the process of implementing its new programs, which include increased testing of ingredients and training for workers. He noted that even the most recent exposures reported by the CDC are now a month old.
"We have indicated before that we expected that we may see additional cases stemming from this, and CDC is now reporting some additional cases," Arnold wrote.
Chipotle co-CEO Steve Ells has told The Associated Press he doesn't think the company will ever know for sure the exact ingredient that sickened customers in the larger outbreak, but that he believes it was bacteria in fresh food like tomatoes or cilantro.
In its annual report, Chipotle has said it may be at a higher risk for outbreaks of foodborne illnesses because of its "fresh produce and meats rather than frozen, and our reliance on employees cooking with traditional methods rather than automation." Those points of differentiation have long been marketing strengths for Chipotle, which has sought to distinguish itself as being of higher quality than traditional fast-food chains.
To begin its image rehabilitation, Chipotle last week took out full-page ads in 61 newspapers around the country apologizing for the illnesses. But it's not clear how long it will take for the chain to regain its footing, and the company rescinded its sales outlook for 2016.
Bill Marler, a food poisoning attorney who is representing customers who were sickened after eating at Chipotle, noted the chain had also been linked to other outbreaks of foodborne illnesses in California and Minnesota this summer.
And this month, Chipotle closed a restaurant in Boston after dozens of students at Boston College reported gastrointestinal symptoms. Those cases were linked to norovirus, and Chipotle has said they were unrelated to the E. coli outbreak.
Still, Marler noted the Chipotle cases pale in comparison to an E. coli outbreak in 1993 tied to Jack in the Box that sickened hundreds and led to four deaths.
Shares of Chipotle dropped 3.5 percent, or $19.07, to close at $522.01. Earlier in trading, the stock hit a 52-week low of $508.10.