Food safety investigations

Day 18: Monday May 25, 2020 (n=9)

An OICC assessment call is held with the following public health stakeholders: epidemiology representatives from British Columbia, Alberta, and Ontario, Health Canada, the Canadian Food Inspection Agency (CFIA), and the Public Health Agency of Canada (PHAC), including NESP and NML.

The following is reported on the call:

NESP: For week 20 (May 10 to May 16, 2020), Salmonella Newport numbers are significantly above expected nationally (11 cases reported, 5 expected) as well as provincially in British Columbia (4 cases reported, 1 expected), Alberta (3 cases reported, 1 expected) and Ontario (3 cases reported, 1 expected). Numbers are within expected levels for all other provinces and territories.

NML: This cluster consists of nine cases (2 BC, 6 ON and 1 AB). The isolates group together within 0-6 wgMLST alleles. Two ON and three BC S. Newport are in the queue for WGS; results expected Friday, May 29. PulseNet Canada has contacted their counterparts at PulseNet USA to determine if there are any Salmonella Newport isolates in the US that have the same WGS; results are pending.

Provincial Updates:

  • Ontario (n=6):
    • They are continuing to investigate all cases of Salmonella Newport. Questionnaires have been received for five of the six confirmed cases. One case is lost to follow up (ON-03).
    • One of the cases (ON-01) is a 20-year-old female with an illness onset of April 22. This case lives with a roommate (ON-02), a 21-year-old female with the same illness onset date. Both cases reported eating similar items including baby spinach in a plastic container, eggs, fruits (e.g., melons, berries, bananas), and supplement products. Both cases report that all their produce comes from grocery store chain 1, and that their spinach was brand X. ON-01 reported she is a vegetarian and does not eat beef, pork, or chicken. ON-02 reported eating chicken purchased from a local butcher shop. Both are university students and reported consuming some meals on campus, but could not remember specific details.
    • ON-04 is a 22-year old male who reported consuming brand Y baby spinach in a plastic bag from grocery store chain 2, beef, as well as chicken purchased from a local butcher shop (same butcher shop as ON-02). The case has a receipt for the spinach purchased, from April 20
      • The local health authority followed-up with the butcher shop that ON-02 and ON-04 purchased chicken. The shop only receives chicken from a provincially registered slaughter plant, which is not distributed outside of Ontario.
    • ON-05 is a 50-year-old male who reported consuming many fruits such as fresh berries, melons, and apples. The case also consumed many fresh meats including chicken and pork, and eats frequently at local diners. The initial questionnaire also lists exposure to nuts and seeds. Illness onset was April 25.
    • ON-08 is a 17-year-old female with an illness onset of May 1 who reported veganism. The bulk of this case’s food exposures appear to be nuts and seeds including walnuts, peanuts, flax, and chia. This case also reported consuming many fresh produce items, especially vegetables; however, further details are limited.
  • British Columbia (n=2):
    • BC-06 is a 27-year-old female case with an illness onset of April 28. The food history on the questionnaire is minimal; however, the case reported consuming many blueberry-spinach smoothies, containing brand X baby spinach in a plastic container and ingredients purchased from grocery store chain 1, nuts and seeds, and has an aversion to dairy products. The only food establishment the case reported eating at is a smoothie bar in her city.
    • BC-09 is a 20-year-old female with an illness onset of May 1, who reported berries, nuts and seeds, whole grain cereal blends, oatmeal, oat bran, and psyllium husk supplements. This case reported never going out to restaurants and making all of her meals at home.
  • Alberta (n=1):
    • Reports that AB-07 declined to be interviewed and is lost to follow-up.


OICC Activation: The outbreak appears to be ongoing and there are some similarities in case exposures reported. Therefore all partners on the call agree to activate a national OICC to facilitate coordination and information exchange among investigative partners.

Next steps: Provinces agree to share the initial questionnaires from the local public health level with PHAC and to allow a PHAC epidemiologist to re-interview their cases using a standardized hypothesis-generating questionnaire, once developed. Using a single interviewer approach will help ensure interviews are done in a relatively standardized fashion and increase the ability to detect patterns/similarities among cases. The provinces will contact the local public health authorities for case contact information to begin the case interviewing process as soon as possible.

Discussion: Partners note that baby spinach is commonly reported, and has been reported by 4/7 cases (ON=3, BC=1). Because all four cases report consuming raw baby spinach, there is information available on purchase location and brand for all 4 cases, and 3 cases report purchasing it in a plastic container, partners express interest in looking into this further.

CFIA will conduct traceback on the baby spinach reported by four cases. While three cases report purchasing from grocery store chain 1 and one case reports purchasing from grocery store chain 2, it is possible those chains obtain spinach from the same distributer, as both grocery stores chains are owned by the same company.

To facilitate traceback and to determine where the baby spinach was sourced from, the provinces will share their cases’ spinach exposure details with PHAC, who will combine it in a line list to share with CFIA after the call.

Another OICC call is tentatively scheduled for Monday, June 1, 2020 and communication will occur over email until the next OICC 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 spinach may have in fact originated from the same imported lot). Do you think it is appropriate to conduct a traceback of baby spinach at this stage? If yes, why baby spinach and not other reported foods?

Yes, it is appropriate to conduct traceback for baby spinach at this point. Spinach has been a vector for Salmonella in historical outbreaks. Packaging details, purchase locations and a purchase date (for one case) are available to facilitate traceback. It would therefore be appropriate for CFIA to look further into baby spinach to see if there are any commonalities (e.g., did grocery store 1 and 2 source their spinach from the same supplier or grower during the case’s exposure periods? Did the two brands come from the same supplier during the time frame of interest?).

Nuts and seeds have also been vectors for Salmonella in historical outbreaks, however, further exposure information and product specificity is not currently available for these food items to support traceback. It would be appropriate to try to gather this information before determining if traceback was warranted.  

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