Schnuck’s and Vaughn’s E. coli Romaine Outbreak – a Long History

E. coli outbreaks associated with lettuce or spinach, specifically the “pre-washed” and “ready-to-eat” varieties, are by no means a new phenomenon. In fact, the frequency with which this country’s fresh produce consuming public has been hit by outbreaks of pathogenic bacteria is astonishing. By way of illustration, in October 2003, thirteen residents of a California retirement home were sickened, and two people died, after eating E. coli-contaminated, pre-washed spinach; in September 2003, nearly forty patrons of a California restaurant chain fell ill after eating salads prepared with bagged, pre-washed lettuce; and in July 2002, over fifty young women fell ill with E. coli O157:H7 at a dance camp after eating “pre-washed” lettuce, leaving several hospitalized and one with life-long kidney damage. And this is just a small sampling of the twenty or more E. coli outbreaks since 1995 in which spinach or lettuce was the source. Several more, including the September 2005 Dole lettuce outbreak, and the infamous September 2006 Dole baby spinach outbreak, appear in the chart below, which is based on information gathered by the Center for Science in the Public Interest:

As of December 4, 2011, 60 persons infected with the outbreak strain of E. coli O157:H7 have been reported from10 states. The number of ill persons identified in each state is as follows: Arizona (1), Arkansas (2), Georgia (1), Illinois (9), Indiana (2), Kansas (3), Kentucky (1), Minnesota (3), Missouri (37), and Nebraska (1).

Among persons for whom information is available, illnesses began from October 10, 2011 to November 4, 2011. Ill persons ranged in age from 1 to 94 years, with a median age of 29 years old. Sixty-three percent were female. Among the 45 ill persons with available information, 30 (67%) were hospitalized, and 2 developed hemolytic uremic syndrome (HUS). No deaths have been reported.

Collaborative investigative efforts of state, local, and federal public health agencies indicate that romaine lettuce sold primarily at several locations of a single grocery store chain (Chain A) was the likely source of illnesses in this outbreak. Contamination likely occurred before the product reached grocery store Chain A locations.

During October 10 to November 4, 2011, public health officials in several states and CDC conducted an epidemiologic study by comparing foods eaten by 22 ill and 82 well persons, including 45 well persons who shopped at grocery store Chain A during the week of October 17, 2011. Analysis of this study indicates that eating romaine lettuce was associated with illness. Ill persons (85%) were significantly more likely than well persons (46%) to report eating romaine lettuce in the week before illness. Ill persons (86%) were also significantly more likely than well persons (55%) to report shopping at grocery store Chain A. Among ill and well persons who shopped at grocery store Chain A, ill persons (89%) were significantly more likely than well persons (9%) to report eating a salad from the salad bar at grocery store Chain A. Several different types of lettuce were offered on the salad bar at grocery store Chain A. Of 18 ill persons who reported the type of lettuce eaten, 94% reported eating romaine lettuce. No other type of lettuce or other item offered on the salad bar was reported to be eaten by more than 55% of ill persons.

Ill persons reported purchasing salads from salad bars at grocery store Chain A between October 5 and October 24, 2011. A total of 9 locations of grocery store Chain A were identified where more than one ill person reported purchasing a salad from the salad bar in the week before becoming ill. This included 2 separate locations where 4 ill persons reported purchasing a salad at each location. For locations where more than one ill person reported purchasing a salad from the salad bar and the date of purchase was known, dates of purchase were all within 4 days of other ill persons purchasing a salad at that same location. Chain A fully cooperated with the investigation and voluntarily removed suspected food items from the salad bar on October 26, 2011, out of an abundance of caution. Romaine lettuce served on salad bars at all locations of grocery store Chain A had come from a single lettuce processing facility via a single distributor. This indicates that contamination of romaine lettuce likely occurred before the product reached grocery store Chain A locations.

The FDA and several state agencies conducted traceback investigations for romaine lettuce to try to identify the source of contamination. Traceback investigations focused on ill persons who had eaten at salad bars at several locations of grocery store Chain A and ill persons at university campuses in Minnesota (1 ill person) and Missouri (2 ill persons). Traceback analysis determined that a single common lot of romaine lettuce harvested from Farm A was used to supply the grocery store Chain A locations as well as the university campus in Minnesota during the time of the illnesses. This lot was also provided to a distributor that supplied lettuce to the university campus in Missouri, but records were not sufficient to determine if this lot was sent to this university campus. Preliminary findings of investigation at Farm A did not identify the source of the contamination. Farm A was no longer in production during the time of the investigation.