The initial, larger STEC O26 outbreak was first detected by public health officials in Washington and Oregon through local foodborne disease surveillance. In late October 2015, officials in those states detected an increase in illness and after interviewing ill people, they determined that illness was likely linked to eating at multiple Chipotle Mexican Grill locations.
A total of 55 people infected with the outbreak strain of STEC O26 were reported from 11 states. The majority of illnesses were reported from Washington and Oregon during October 2015. The number of ill people reported from each state was as follows: California (3), Delaware (1), Illinois (1), Kentucky (1), Maryland (1), Minnesota (2), New York (1), Ohio (3), Oregon (13), Pennsylvania (2), and Washington (27).
Among people for whom information was available, illnesses started on dates ranging from October 19, 2015 to December 1, 2015. Ill people ranged in age from 1 year to 94, with a median age of 21. Fifty-seven percent of ill people were female. Twenty-one (38%) people reported being hospitalized.
In December 2015, a second outbreak of a different, rare strain of STEC O26 was identified. A total of five people infected with this strain of STEC O26 were reported from three states. The number of ill people reported from each state was as follows: Kansas (1), North Dakota (1), and Oklahoma (3).
Among people for whom information was available, illnesses started on dates ranging from November 18, 2015 to November 26, 2015. Ill people ranged in age from 6 years to 25, with a median age of 22. Eighty percent of ill people were female. One (20%) person reported being hospitalized.
The epidemiologic evidence collected during these investigations suggested that a common meal item or ingredient served at Chipotle Mexican Grill restaurants was a likely source of both outbreaks. The investigations did not identify a specific food or ingredient linked to illness in either outbreak.