This case study covered an outbreak investigation of a fictitious Salmonella Newport outbreak from the federal perspective. All outbreaks are unique and the case study was not intended to be a guidance document for outbreak investigation in Canada. In order to improve the story flow, several creative liberties were taken. A selection of those creative liberties are summarized below:

Case study story


There is a very short reporting delay between the onset date of cases and the reporting of these cases to the outbreak team (19-26 days).

The timelines for detection of cases used in this case study are not reflective of the actual reporting delay commonly seen in Salmonella outbreaks, commonly 3-6 weeks.

Specific product details for spinach were known from initial interviews, but were limited for other products.

It is unlikely that this level of detail (purchase date, brand) would be available upon initial interview for 4 cases, or that  cases coincidentally only have that level of detail available for one exposure (spinach).

Date of illness onset was provided for all cases, even those lost to follow up.

Date of illness onset is not typically available for all cases. When it is not available, the earliest date available should be used (specimen collection date, received date, isolation date, report date).

Seven interviews were completed using the hypothesis-generating questionnaire within 24 hours.

Turnaround time is often much longer than one day. It can take several days to obtain contact information for a case, get in touch with them and find a convenient time to administer the questionnaire.

In the case study, most of the information was shared during the OICC calls.

While OICC calls offer a great opportunity to provide updates, information is typically shared as it becomes available, which does not always align with the OICC call schedule.

The majority [10/12 (83.3%)] of cases interviewed with a hypothesis-generating and/or focused questionnaire reported consuming or probably consuming chia seeds prior to onset of illness.

% reporting implicated product is not always this high. Epi assessments are often made with less than 100% of cases reporting consumption of the product of interest.

No cases are reported with onset dates after the recall.

The recalled chia seeds would have a long shelf life. People are not always aware that they have recalled product in their homes, and therefore it is possible that additional cases may arise after the recall.

Health Canada assigned a Health Risk 2 for the two different brands of chia seeds: “Smile” brand (two lot codes) and “Nature’s Planet” brand (one lot code). CFIA determined that the appropriate risk management action was a Class I recall to the consumer level with a Food Recall Warning. The company agreed to conduct the voluntary recall.

Health Canada and CFIA did not review this case study. The health risk assigned and risk management action taken in this case study may not necessarily reflect the determinations that Health Canada and CFIA would make based on the available information.


A post-outbreak debrief was not held for this investigation.

For an outbreak of this complexity a post-outbreak debrief would be held and recommendations would be made. These would be captured in the final investigation summary. A linelist of chia seed exposures for each case would also be included in the final investigation summary, listing all the product details, loyalty card information, etc.


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