On August 22, 2000, Marion County Health investigators contacted the Oregon Health Department to report that a number of County residents were suffering from E. coli O157:H7.  Three days later Wendy’s International, Inc voluntarily closed its Salem restaurant.  The findings by the Marion County Health Department made the link to this Wendy’s restaurant clear:

The matched case-control study implicated Wendy’s Restaurant at 2375 Commercial Street SE in Salem as the source of this outbreak of E. coli O157:H7 infection.  Molecular sub-typing linked the first nine cases to eight additional cases, including one whose only exposure to Wendy’s was a [Wendy’s] restaurant in Tualatin, Oregon….

See Outbreak Investigation Report.  Reinforcing the fact that this outbreak had its common source at the Salem Wendy’s restaurant, the health department determined that “[n]o cases of infection caused by this strain of E. coli O157:H7 with illness onset after August 25, 2000, have been detected in Oregon or elsewhere.”

In its published Outbreak Investigation Report, the health department defined the outbreak victims as follows:

confirmed case:  a person with laboratory-confirmed E. coli O157 infection with onset after eating at Wendy’s Restaurant on SE Commercial Street in Salem (Oregon) since August 7, 2000 OR with E. coli O157 infection of the same molecular subtype confirmed by PFGE after eating at any other Wendy’s Restaurant since August 7, 2000;

presumptive case:  a person who developed bloody diarrhea within 7 days of eating at Wendy’s Restaurant on SE Commercial Street in Salem between August 14 and 18, 2000 (the exposure dates of confirmed cases);

suspect case:  a person who developed non-bloody diarrhea within 7 days of eating at Wendy’s Restaurant on SE Commercial Street in Salem between August 14 and 18, 2000 (the exposure dates of confirmed cases);

secondary case:  a person with bloody diarrhea or laboratory-confirmed E. coli O157 infection who did not eat at a Wendy’s Restaurant during the week before onset of diarrhea, but who developed this illness within 7 days of the onset of laboratory-confirmed or presumptive E. coli O157 infection in a household member who ate at Wendy’s Restaurant on SE Commercial Street in Salem between August 14 and 18, 2000, OR a household member of a case with E. coli O157 infection of the same molecular subtype confirmed by pulsed field gel electrophoresis after eating at any other Wendy’s Restaurant between August 14 and 18, 2000.

The health department investigation revealed that cross contamination from contaminated ground beef may have been the outbreak source, as a number of victims had not eaten ground beef products.  The role of cross-contamination as the source of other major E. coli O157:H7 outbreaks has been well documented.  Independent events of cross-contamination from beef within the restaurant kitchens, where meats and multiple salad bar items were prepared, were the most likely cause of four separate chain-restaurant associated outbreaks in Washington and Oregon in August, 1993.  See Lisa A. Jackson, M.D., et al., “Where’s the Beef?”, Archives of Internal Medicine, Volume 160, August 14/28 2000, 2380-2385.

Marion County Inspectors found several food-handling problems that likely resulted in cross-contamination, causing E. coli O157:H7 bacteria in the meat to contaminate other foods.  These included:

  • Food-preparation staff soaked lettuce in the first compartment of a three-compartment sink that was used to rinse bloody-meat-juice-covered pans in which raw hamburger patties had been held, without cleaning and sanitizing the sink between uses.
  • Food-preparation staff used a cleaning and sanitizing “wet towel, dry towel” process, whereby a shelf above the grill that held raw hamburger patties was wiped clean first with a dry towel, then with a sanitized-soaked wet towel.  The dry, bloody-meat-juice-soaked towel was used for hand wiping in both the grill area and the sandwich assembly area (where raw products are placed on cooked burgers).
  • Poor hand washing was observed.

Prior to reopening, the restaurant was required to do the following:

  • Handwash Sink/Produce sink in Prep area to be switched to improve accessibility at back prep area handwashing.
  • A new handwash sink will be provided in the grill/sandwich prep area.
  • All open foods/not sealed will be removed from the facility and replaced with new product.
  • A new utensil washing system will be installed.
  • A barrier will be provided to separate the grill from the sandwich assembling area.
  • In the near future, a food preparation sink will be installed at the baked potato station.
  • Prior to reopening, training and re-orientation will be provided to all staff over food preparation procedures.  Initially at the Commercial St. store and then all other Marion County Facilities.
  • Increased monitoring of cooking hot/cold holding, sanitizer rotation and towel rotation.

The evidence gathered from the report establishes that cross-contamination occurred between the meat that was supplied to both the Salem and Tualatin Wendy’s Restaurants and other food items that did not undergo further cooking (or a “kill step”).

A variation of the cross-contamination theme occurred again in early August 2006 when public health officials in Weber County, Utah, became aware of several people who attended a teachers’ conference luncheon and had contracted E. coli O121:H19 infections.  On August 2, 2006, the Weber-Morgan Health Department (WMHD) issued a News Release indicating that three people had been infected with E. coli O121:H19, and that two of the individuals had developed HUS.  See August 2, 2006 Press Release. WMHD stated that the evidence indicated that all three people contracted E. coli from the same source sometime during June 27-30 at a restaurant in the Ogden, Utah area.  By August 7, WMHD officials had revised the number of outbreak victims to four, including three who had developed HUS.  See August 7, 2006, Press Release.

WMHD further concluded that the source of the infection was contaminated iceberg lettuce prepared at the Wendy’s Restaurant at 2500 North 400 East in North Ogden, Utah. One of the patients with confirmed HUS, who had not attended the teacher’s conference, had eaten cheeseburgers with iceberg lettuce at the Wendy’s Restaurant during the outbreak period.  The second confirmed HUS case was an attendee of the teachers’ conference, and a third case of HUS was determined to be secondary transmission from an infected person at the conference.

Eventually, WMHD determined that at least 69 people had become ill in the outbreak. Of the sixty-nine people who reportedly became ill, four remained hospitalized and were in serious condition.

Investigators conducted a study of the persons who had attended the teachers’ conference to determine the extent of illness among the attendees.  WMHD contacted and interviewed 225 individuals who had attended the conference and consumed food from Wendy’s.  Of this number, 69 (31%) became ill.  WMHD determined that the likely exposure period was between June 27 and 30.  Onset of illness occurred between June 27 and July 26, with the majority of the cases occurring between July 4 and July 12.

Part of the WMHD investigation included a thorough inspection of three establishments that catered to the teachers’ conference.  The only common food item shared by those who became ill from E. coli was iceberg lettuce from the North Ogden Wendy’s restaurant.

One of the HUS patients with E. coli O121:H19 was laboratory confirmed by stool culture.  DNA subtyping by Pulsed Field Gel Electrophoresis (PFGE) showed that one of the individuals that was not associated with the conference, but who had consumed cheeseburgers from Wendy’s during the outbreak period, was an identical genetic match to one of the previous confirmed E. coli cases associated with Wendy’s.