Food safety investigations

 Day 2: Tuesday July 22, 2014 (n=6)

An OICC assessment call is held with the following public health stakeholders: epidemiology and laboratory representatives from Alberta, Saskatchewan and Manitoba, Health Canada, the Canadian Food Inspection Agency (CFIA), and the Public Health Agency of Canada (PHAC).

The following is reported on the call:

  • Alberta (n=1): the case is a 35-year old female, with no travel outside the province during her incubation period. The case reports eating hamburgers (well done), grilled chicken, and various salads. Case has a dog. Date of onset: July 4, 2014.
  • Saskatchewan (n=3):
    • Local public health has conducted an initial investigation into the two cases associated with a Canada Day BBQ; there are 5 other non-laboratory confirmed (clinical) cases that attended the BBQ that the health unit has begun interviewing (stool samples not provided at this time).
    • Suspect source 1: Hamburgers
      • Canada Day BBQ
        • The BBQ host was contacted, and reported purchasing fresh ground beef to make hamburger patties at home before the event as well as using pre-made frozen hamburgers.
        • There are no hamburgers or ground beef left over.
        • The BBQ host does not recall any brands and is unsure of when and where they purchased the products. They listed four different chain grocery stores where they shop regularly.
        • The person does not have any loyalty cards, nor do they keep receipts in a systematic way.
        • Local public health is trying to follow up with the person to try and obtain more information on potential dates and the locations of the stores.
        • All information has been provided to the CFIA.
        • Saskatchewan asks Alberta if they can find out whether their case can recall any details about the hamburger they consumed.
    • Suspect source 2: Romaine lettuce
      • The brand of romaine lettuce was served at the Canada Day BBQ was shared with CFIA.
      • Two of the non-laboratory confirmed (clinical) cases are vegetarians who did not consume any hamburgers.
      • One other case who did not attend the BBQ but also ate burgers reported eating the same brand of romaine lettuce served at the BBQ.
      • Saskatchewan asks Alberta if they can find out whether their case consumed romaine lettuce of the same brand.
  • Manitoba (n=2): no questionnaires received for either case from local public health yet.
  • CFIA: traceback activities have begun for the romaine lettuce reported being eaten by cases in Saskatchewan. The information obtained to date on the ground beef and frozen hamburgers is insufficient to start a full traceback. Local public health in Saskatchewan is trying to determine when and where the beef products were purchased.

Everyone on the call agrees to activate a national OICC for this investigation.

The next OICC call is tentatively scheduled for Monday, July 28, 2014. The group decides to communicate via email until the next call.

Question 2-1: Food safety investigations can help assess the nature and extent of the food safety hazard and identify actions to either eliminate or minimize potential risks to the public (e.g., recall the affected products). By using traceback methods, the investigation can identify whether the implicated product(s) are linked in the production chain (e.g., two different brands of lettuce may have in fact originated from the same imported lot). Do you think it is appropriate to conduct a traceback of ground beef, frozen hamburgers, as well as lettuce at this stage?


Yes, it is appropriate to try to conduct all three food safety investigations at this point. Lettuce, ground beef, and hamburgers are all plausible sources of illness for E. coli O157:H7, and have been associated with outbreaks in the past.

  • All (4/4) of the confirmed cases with known exposures report eating salad/lettuce (SK=3, AB=1).
  • All (4/4) of the confirmed cases with known exposures also report eating ground beef/hamburgers (SK=3, AB=1).
  • While two of the non-laboratory confirmed (clinical) cases identified as part of the Saskatchewan Canada Day BBQ are vegetarians and report not eating any hamburgers, cross-contamination of the lettuce from hamburgers is possible.