On July 17, 2002, Spokane Regional Health District (SRHD) contacted the Washington State Department of Health (WDOH) to report a cluster of diarrheal illnesses among a group of teenaged girls who had recently attended a drill team dance camp at Eastern Washington University (EWU). Laboratory tests conducted at the WDOH Public Health Laboratory later confirmed the illnesses to be E. coli O157:H7 with an indistinguishable PFGE pattern. Subsequently, SRHD became aware of additional cases of E. coli O157:H7 with the same PFGE pattern that had no association with dance camp and EWU. This led to a broader investigation by a number of public health agencies.
The epidemiologic investigation revealed two groups or “clusters” of persons with E. coli O157:H7. Infected persons in both groups shared an indistinguishable PFGE pattern. The first group consisted of 55 cases of E. coli O157:H7, 34 of which were culture-confirmed, among those who worked at or attended the dance camp at EWU. A second group who attended a church camp consisted of 14 persons, including one culture-confirmed case of E. coli O157:H7. It was quickly determined that illnesses at the church camp were secondary to the dance camp outbreak. Several of the young women who had attended the dance camp went on to attend the church camp immediately thereafter.
In addition to the two clusters originally identified, several other culture-confirmed E. coli O157:H7 cases with a PFGE pattern indistinguishable to the dance team outbreak pattern were reported to WDOH. None of these cases had any connection whatsoever to either the dance camp or church camp. Collectively, these cases were classified by investigators to be “outliers” because they were not part of the core group of associated outbreak cases.
WDOH and SRHD’s epidemiologic investigation resulted in the determination that the probable source of the E. coli infections was romaine lettuce. The trace back investigation conducted by WDOH revealed that the romaine lettuce served at the camp in the relevant time frame was shredded, bagged, and sold by Spokane Produce.
The second group of illnesses was determined to be secondary infections that resulted from exposure to one or more persons who had developed E. coli O157:H7 infections after consuming romaine lettuce supplied by Spokane Produce while attending the dance camp at the EWU campus. The later dates of onset of these infections reflected the additional time necessary to complete the second exposure and incubation periods.
In addition to the two main clusters, health investigators were able to link all of the individuals considered to be “outliers” to consumption of Spokane Produce romaine lettuce, and at the conclusion of the investigation, WDOH concluded that the source of the outbreak was romaine lettuce prepared and sold by Spokane Produce:
This romaine-associated outbreak of E. coli O157:H7 included cases from a cafeteria dinner on a Spokane campus, lunch the following day from the same cafeteria, a restaurant salad in Spokane County, romaine purchased at several Spokane area grocery stores, two restaurant salads in Walla Walla County, and romaine served at a restaurant in a Midwestern State. Cases were clustered in time, and no outbreak associated isolates were subsequently identified through PulseNet.
Marler Clark represented several girls who attended the dance camp at Eastern Washington University in claims against Spokane Produce, including one girl who developed hemolytic uremic syndrome (HUS). The firm also represented individuals who became ill with E. coli after eating Spokane Produce lettuce, but who were not part of the dance camp outbreak. The claims were resolved in 2006.