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Chipotle’s Norovirus Outbreak Is Not A Typical Norovirus Outbreak

The avalanche of norovirus cases linked to a Boston Chipotle is one of the biggest outbreaks since 2009. Eighty cases have been confirmed by the Boston Public Health Commission to date, and Boston College reports that at least 140 students have come to the campus health center with norovirus-like symptoms since the outbreak began over the weekend. Those symptoms include: nausea, vomiting, cramps, diarrhea and muscle pain. So, the fun stuff.

Just under 3 percent of the food-related norovirus outbreaks that the Centers for Disease Control and Prevention tracked from 2009 to 20141 sickened 80 or more people. Only 1.3 percent of outbreaks sickened 140 or more people. Half of all outbreaks sickened 11 or fewer people.

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It’s not just the size of the outbreak that’s unusual — it’s where it happened. Although norovirus is the most common cause of food-related illnesses nationwide (about 50 percent of outbreaks), it’s not the most common cause of illnesses at fast-food outlets like Chipotle. Since 2009, when the CDC began tracking where outbreaks occurred, fast-food restaurants have been much more likely to give their patrons salmonella than norovirus (28 percent of illnesses at fast-food chains were linked to norovirus, while 43 percent were linked to salmonella). Sit-down restaurants have the opposite risk profile (45 percent of illnesses linked to norovirus, 25 percent to salmonella).2

In better news for Bostonians who are sick, only 1 percent of people who caught food-related norovirus from 2009 to 2014 required hospitalization. And food-related norovirus outbreaks were linked to only three deaths over those six years; that’s 0.01 percent of all those who were sick.


  1. 2015 data is not yet available.
  2. The CDC often lists more than one disease as linked to an outbreak. I have counted all outbreaks in which either salmonella or norovirus was implicated, but these diseases may not have caused all illnesses linked to the outbreak.

Leah Libresco is a former news writer for FiveThirtyEight.

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