Boston College said Tuesday the number of students complaining of gastrointestinal symptoms after eating at a Chipotle this weekend has climbed to 80, up from the 30 it reported the previous day.
The illnesses come as Chipotle's sales are already being slammed by a multi-state outbreak of E. coli linked to its restaurants. The company says it thinks the Boston College illnesses are an isolated case of norovirus and unrelated to the E. coli cases.
"All of the evidence we have points in that direction," said Chris Arnold, a Chipotle spokesman.
Boston College said it is working with state health officials and that all students who reported symptoms have been tested for both E. Coli and norovirus. It said results will not be available for at least two days.
According to a report from the Boston Inspectional Services department, which is responsible for inspecting the city's restaurants, an employee at the Chipotle restaurant in Cleveland Circle was sick while working a shift Thursday.
William Christopher, the department's commissioner, said it was not immediately known if management at the Chipotle was aware of the employee's symptoms. He said the restaurant's permit to operate has been suspended by the city and that a disinfection process has begun.
According to the Centers for Disease Control and Prevention, infected workers cause about 70 percent of reported norovirus outbreaks from contaminated food. Each year, norovirus causes 19 million to 21 million illnesses.
The virus can spread from an infected person, contaminated food or water, or by touching contaminated surfaces, the agency says. It is very contagious and can spread quickly in places such as daycare centers and cruise ships.
Common symptoms include diarrhea, vomiting, nausea and stomach pain.
The CDC has not yet determined the ingredient responsible for sickening 52 people in the E. coli outbreak, but 47 of the individuals reported eating at a Chipotle before they got ill. The first cases were reported at the end of October in Oregon and Washington, with additional cases later being reported in seven other states.
The most recent illness started Nov. 13.
At a presentation Tuesday for analysts in New York City, Chipotle executives noted the exposure period for the E. coli cases appears to be over. The company has said it is tightening its food safety procedures, and that some of its local produce suppliers might not be able to meet the new standards.
Executives said the chain may eventually raise prices to make up for its investments in improving food safety.
In its annual report, Chipotle has noted that it may be at a higher risk for outbreaks of food-borne illnesses because of its "fresh produce and meats rather than frozen, and our reliance on employees cooking with traditional methods rather than automation."
Chipotle Mexican Grill Inc., based in Denver, has more than 1,900 locations, primarily in the U.S. The company has already warned that sales are expected to fall as much as 11 percent at established locations for the fourth quarter as a result of bad publicity from the E. coli cases.
That would mark the first time the sales figure has declined since Chipotle went public in 2006.
Chipotle shares fell $8.75, or 1.6 percent, to $543 in afternoon trading Tuesday.