Podcast: Guest Episode: How are foodborne illness investigations conducted?

Clinton Monchuk: (00:07) 
From Canadian Food Focus, this is Ask a Farmer. I’m your host Clinton Monchuk, a Saskatchewan farmer. In this podcast, we talk to food experts to answer your questions about your food.  
 
Clinton Monchuk: (00:29) 
Welcome to the Ask a Farmer podcast, everyone. Can you imagine a team of detectives working tirelessly around the clock to solve mysteries that affect public health? It’s kind of like Matlock. On today’s podcast, we’re shedding light on foodborne illness investigations, and a guest podcast episode from Inspect and Protect, the Canadian Food Inspection Agency’s podcast with host Michelle Strong and Greg Rogers. Today’s expert panel of guests includes Tana Kershaw and Courtney Smith from the Public Health Agency of Canada’s Outbreak Management division, Fred Jameson, the Food Safety Recall Specialist in the Food Safety Investigation Recall Unit, and Angela Catford, section head of Health Risk Assessment at Health Canada. From identifying outbreaks to tracing contaminated foods, their work is essential in safeguarding our health. Stay with us as we explore how these experts collaborate during outbreaks from initial detection to risk assessment and more.  
 
Michelle Strong: (01:44) 
If you thought you had food poisoning, would you report it? Would you get tested? When it comes to foodborne illness outbreaks, there are teams of detectives working tirelessly around the clock to find the culprits and save lives.  
 
Greg Rogers: (01:59) 
This episode, we’ll be speaking with four of these detectives who’ve investigated many cases across Canada. Alright, Michelle, let’s introduce our guests.  
 
Michelle Strong: (02:08) 
Hi Courtney. Hi Tanis. Do you want to introduce yourselves?  
 
Tanis Kershaw: (02:11) 
Sure. Thank you so much for having us. So, I’m Tanis Kershaw. I’m currently an acting manager with the Outbreak Management Division at the Public Health Agency of Canada.  
 
Courtney Smith: (02:21) 
Hey, and yes, my name is Courtney Smith. I’m a senior epidemiologist and I work right alongside Tanis in the Outbreak Management Division. You know, by the book, you might see an epidemiologist defined as someone who investigates you know, patterns and causes of disease and more informally, we often explain the role of an epidemiologist as sort of a disease detective, and I’m doing air quotes for those who, who can’t see me, who are listening in.  
 
Tanis Kershaw: (02:48) 
I do think of us like detectives. I’m not sure if you know, real detectives would appreciate the analogy, but the disease detective that Courtney mentioned, I really do feel like we are looking for clues and pieces of evidence and trying to put that all together.  
 
Michelle Strong: (03:03) 
Next, we want to introduce you to Fred, a food inspector at the Canadian Food Inspection Agency.  
 
Fred Jamieson: (03:08) 
Hello, I’m Fred Jamieson. I’m the food safety recall specialist with the office of Food Safety Recall in the food safety investigation recall unit. I’m a little bit of Sherlock Holmes, a little bit of CSI because you kind of use the deductive reasoning to create a hypothesis of the potential source of route. However, you know, unlike the TV show, it takes longer than 45 minutes plus commercials to conduct a food safety investigation. There’s no machine that you can put a sample in and get a result in two minutes. And finally, we don’t get to carry guns, which is probably good because that’s a thing I’d probably shoot my toe off or something like that. .  
 
Michelle Strong: (03:49) 
And finally we have our fourth detective, Angela.  
 
Angela Catford: (03:52) 
So my name is Angela Catford and I am the section head of the Health Risk Assessment Section at Health Canada. I’ve actually been in the food safety and in the risk assessment world for over 13 years now. It’s an expertise you kind of build up over a long time.  
 
Greg Rogers: (04:10) 
Have you ever gotten sick yourself from food?  
 
Michelle Strong: (04:13) 
What a question. 
 

Angela Catford: (04:14) 
Okay, it’s our greatest fear to hold a work potluck and have an outbreak associated from our team.  
 
Greg Rogers: (04:25) 
Hi, I am Greg.  
 
Michelle Strong: (04:26) 
And I’m Michelle. And this is Inspect and Protect, the Canadian Food Inspection Agency’s official podcast  
 
Greg Rogers: (04:32) 
All about food safety, animal health, and plant health. So how do you go about investigating a foodborne illness outbreak? Like, can you walk us through kind of a step by step how it usually goes?  
 
Tanis Kershaw: (04:45) 
So, in terms of how we detect the outbreak, first, people have to be exposed to the contaminated food and become sick and then seek care. So they need to go to the hospital or to a physician to, or to have a stool specimen tested. So if it comes back positive for something like e coli or salmonella, then what will happen is it will be reported to the local public health unit where that person lives. Someone will call them up from the local public health unit and they’re going to ask them questions about the foods they ate before they got sick, animal contact they might have had, travel, water exposures… At the same time, it’s also going for further laboratory testing.  
 
Fred Jamieson: (05:26) 
When there’s an identification that there’s a foodborne illness, and in particular, where then by definition that there’s two or more, then it’s an outbreak. So the first step is identifying the trigger. So this was being notified there’s an outbreak. That’s the trigger. The next step is investigating.  
 
Angela Catford: (05:45) 
And that’s where the public health agency can kick in and they’re trying to say, okay, I have to start solving this mystery.  
 
Tanis Kershaw: (05:54) 
So just to set the stage, Courtney and I work at the Outbreak Management Division, which is in the Center for Foodborne Environmental and Zoonotic Infectious Diseases, part of the Public Health Agency of Canada. So we coordinate the overall investigation and we also conduct the epidemiologic part of the investigation.  
 
Courtney Smith: (06:12) 
While investigating our outbreaks, we do have like a lot of different tools in our tool belt, but the main one is definitely case interviewing and the focus is gathering those very specific details on what the cases ate before they were sick. So essentially as part of that re-interview process, we’re calling each case in an outbreak to ask them what they might have eaten in a certain number of days before they were sick. And our goal ultimately is to find, you know, the commonality across all of the cases and the source of the outbreak. But of course, like anything, there’s a catch. It can often take, you know, four to six weeks between when a person is sick and between when we’re giving them a call for this re-interview. But luckily we have a lot of expert interviewers and they have a lot of different strategies to help our cases, remember what they might have eaten one or even two months ago, sometimes even longer.  
 
Tanis Kershaw: (07:02) 
So we’re going to be looking at, is there anything in common in among these people in terms of the foods they ate, are they all reporting? Are they all healthy eaters reporting a really, you know, fruit and vegetable type diet? Or are they all reporting a very specific type of one food? We’re also looking at age. Are they all different ages or are we seeing a lot of young children in a cluster which might give us a clue, you know, what would they be eating that might be different from other age groups? And so we’re also looking at where people live. So urban versus rural in particular can be a helpful clue, because if you live in a small town, there might only be one grocery store that you get your food from, and that might just limit the availability of different food items.  
 
Courtney Smith: (07:49) 
We might be asking even more questions about, for example, you know, if they can look into their bank statements or their credit card transactions to see if they went to a restaurant that day or went to the grocery store or a cafe. We might ask if they have receipts from any grocery store purchases for that time period. You know, a lot of people these days are taking photos of food, you know, on their phone. So we can ask them to look back at their phone to see if they have any pictures of you know, particularly aesthetically pleasing meals they might have photographed during the time that we’re interested in. And we can even ask our cases about their loyalty card information. So for example, a lot of grocery stores these days, you go in, you have a card and you’re collecting points, you know, with a case’s consent, we can take their loyalty card number, follow up with that grocery store, and then get a detailed record of everything they purchased in a very specific timeframe.  
 
Tanis Kershaw: (08:46) 
So we might’ve learned you had a salad, but now we want to know every ingredient that was in the salad, the dressing that was used, did you make it yourself? Where did you purchase it from? And then we also are looking for food safety information as well. So that’s where we work very closely with the Canadian Food Inspection Agency. So looking at, you know, trace back, one piece that’s very helpful for us is supplier information. Sometimes we might see people reporting everyone’s reporting yogurt, for example, but it’s all different brands. Well, is it possible that these brands could be made at the same place? That’s something that CFIA would be able to, you know, look and see if that’s a possibility. It helps us rule in or out different items as potential sources.  
 
Fred Jamieson: (09:31) 
So, what we’ll do is that based on the information we get, we kind of do the tracing of the foods from the consumer back through the retail, and then possibly in the case of hotel, restaurant, institution issues back through distribution to production, to the processing facilities to pinpoint, you know, the suspect source of the problem. So it’s like much like in a criminal investigation that everything seems to point at a particular food. If we’re lucky, if they gave up a particular product with a particular brand and a code, then what we would look at is we would reach out to the company to start getting information on that particular product, the volume where it was shipped and, and sent, you know, if there’s a shelf life. And then at the same time we’re looking at if it’s within Canada. So we’re trying to get like production records: the volumes, was there any quality assurance issues? Was there any sampling based on the nature of the, say it’s a pathogen, which is going to cause a foodborne illness? Do they do testing for it? Have they had a problem? Is there any indication there? So you’re trying to build that case to build documented evidence. Now what would happen is how many different products were involved, because normally it could be one product, sometimes you could have several. Sometimes they give us almost like a laundry list or a grocery list of products. And so, you know, we’ve had that. So a lot of it is that the initial information, can we confirm the suspect? You have to kind of like, almost like an onion. You do the first one, then you go back and you do the same investigation until you literally go and find it. It can go very quickly if it’s singular, but in some cases they will bring us a list of a lot of products and we have to run each down. And that can take weeks or even longer until we can get the confirmation. We have to literally go through each one and take them off the list of suspects.  
 
Angela Catford: (11:15) 
So public health starts the, the ball rolling. When we start suspecting different food sources, the Food Inspection Agency hops in and starts doing food safety investigation. They’re going to start looking for what’s going on at different places where food is made or manufactured. Maybe they’re going to go take some food samples and do some testing for the different bacteria or parasites or viruses. And all the time that this is happening, we’re all continually meeting all the different folks at public health, food inspection and Health Canada. And we’re on the phone talking to each other. And then when we start to have a clearer picture and we say, okay, we know what’s causing this from the hazard point of view, the bacteria or the virus, and we have a suspicion about what food is involved, then they’re going to pass the ball to our court and we’re going to do our risk assessment at Health Canada.  
 
Angela Catford: (12:13) 
And then finally we say, okay, we have an understanding. How bad would it be? You know, what’s the hazard? How sick could it make someone? Is it possible? And how did it get there and how much might been there when someone ate the food? And then we’ll make a determination about the risk. So, we put it together and we identify a level, and the level could be either a health risk one, which is the most serious; health risk two; health risk three. And you know, it’s possible that we can take a look at everything and say, you know, there’s no health risk too. Or that the whole situation doesn’t result in a health issue really for Canadians. Once we do the risk assessment, it goes back to the Food Inspection Agency.  
 
Fred Jamieson: (13:00) 
So then a decision is made by the Agency, they’ll do a recall, and in the case of an outbreak and a pathogen in a product, it would go to a public release. So we’ll notify the company that, you know, we’re requesting a recall. The company would then either say yes or no, whether doing the recall. 
 
Greg Rogers: (13:17) 
Does anyone ever refuse to recall the product?  
 
Fred Jamieson: (13:20) 
Since 1999, there’s been approximately about 10,000 recalls. And in that time, we’ve only had seven what we call mandatories. And this is where again, if a company is not available or not willing to conduct a recall voluntarily, the Minister of Health, under the Canadian Food Inspection Agency Act can order a company to recall a product where the Minister believes that it poses a risk to the public, animal and public health. So, when you think only seven mandatories out of over, you know, close to 10,000 recalls, and the first one was in 1999, just after, you know, the agency was kind of created. And the last one was actually in April, 2004. So I think those were learning moments for the industry. Initially, they waited for the investigation and the decision, but now many companies are now conducting their own assessments. And so they will come to us and say, based on our information, we want to take this product off. So they do it and more and more because of after, you know, 23, 24 years, the industry has learned to get ahead of it. And they’ve always been very good at doing the right thing at the right time once the information comes up. 
 
Greg Rogers: (14:37) 
If you aren’t already receiving food recall alerts, we suggest you sign up using our link in the description. You’ll be notified of products that are being recalled for all kinds of reasons, including allergens and food safety.  
 
Michelle Strong: (14:51) 
Tanis, you mentioned laboratory testing. Can you tell us more about it?  
 
Tanis Kershaw: (14:56) 
So one of the main methods that we use is called whole genome sequencing. And this is a laboratory method that is essentially DNA fingerprinting for a bacteria. So for something like e coli, the bacteria have individual DNA fingerprints, genetic fingerprints, just as people have genetic fingerprints as well. So then what we do is the, these go into a national database at the National Microbiology Laboratory. And so the ones that the bacteria that have a similar strain, they are more likely to be coming from a common source. And this is the main way that we learn about new clusters of illnesses that are all kind of part of this same genetic profile.  
 
Michelle Strong: (15:39) 
How quickly does all that happen? Like I’m just picturing waiting in the emergency room, they’re like, you’re fine, Michelle, go home, or…?  
 
Tanis Kershaw: (15:49) 
It can definitely definitely take some time. So, you know, once you get your specimen collected, it can take a few days for testing. It has to go through kind of the whole chain, from the time the person actually is tested, from the time we learn about it can be four to six weeks. So it’s definitely a big time lapse there. You likely will know that you have, e coli or have salmonella within a couple of weeks or a shorter period of time. But to do that further, laboratory testing does take a little bit more time.  
 
Greg Rogers: (16:18) 
So we talked about the successful investigations, but are there like cold case files, like the ones that got away that you just never [resolved].Ooh, never. Like I’m thinking like the seasoned detective, you know, had this one criminal that was just, you know, they could never track down.  
 
Michelle Strong: (16:39) 
This is true detective work!  
 
Courtney Smith: (16:41) 
For sure. I mean, we don’t have a one hundred percent success rate. We give it our all for every outbreak. We have a motto to leave no stone unturned. But you know, certainly we’re not always successful for a variety of reasons.  
 
Fred Jamieson: (16:55) 
Some of the challenges we have is, is the inability to find the root source or cause. And so this happens often with outbreaks associated with the consumption of short shelf life vegetables. Good example: like leafy greens, romaine lettuce. So when you look at it that by the time the product is harvested, shipped, put on retail, you purchase it, you eat it, that could be a couple days later. Now you’re not feeling well. You go to the doctor, you have to give a specimen that has to be analyzed. It has to go off and have this isolate or the genetic fingerprint done. Weeks go by and on a shelf life, so then what happens is that then you have a challenge where, by the time it comes to us and the information that there’s an outbreak, the products that are suspect, there’s no samples available, so we can’t confirm it. And then given the nature of some of the fresh greens that are harvested, they do them by different states and fields as they move around. So it’s sometimes like it’s very difficult to identify.  
 
Tanis Kershaw: (17:58) 
If we don’t find the source, it means the outbreak has ended. So we would never stop investigating if new cases are continuing to be reported and we haven’t identified what that source is. We’re always going to keep investigating until it either ends or we’ve identified the source.  
 
Fred Jamieson: (18:13) 
We had an issue with leafy greens, romaine lettuce, where it actually took three years of recalls until every year we got a little closer until I think it was the third year that they actually identified the source. And this is, and again, when you look at some greens, they’re mixing and matching and adding a variety of different lettuces from different sources. If you go to the grocery store and you find one of these mixed greens packs, which source is it? So this is where it becomes challenging, where you got a variety of different ingredients on short levels. So that’s, one of the biggest issues, challenges.  
 
Michelle Strong: (18:49) 
You’ve got me so curious. So what was like the most notable foodborne illness outbreak you’ve ever worked on?  
 
Tanis Kershaw: (18:56) 
Well, I’ll go first. There’s so many. Tanis, you go first with yours. For me, I’ve worked on quite a few over the years, but one of the most interesting ones for me is still one of the first ones I worked on, which was an e coli outbreak that was found to be linked to flour. And flour was not a known source really at the time. So it wasn’t something that was already on our questionnaire. And it was the first time that this was identified in Canada. So it was quite a challenge because as you can imagine, flour is not a food people eat. If I asked you about what you ate in the last 10 days, it’s, I’m thinking almost no one, no one is going to say I ate flour because it’s an ingredient. So people are using it in baking, but they’re also using it to make sauces, gravy, homemade Play-Doh, even in some beauty products. But another challenge with flour is that a lot of people transfer the flour into a separate container in their house. So there’s no lock code or best before date. There’s no packaging. Even if you didn’t remember the brand you bought, you know, you don’t have that bag anymore.  
 
Michelle Strong: (20:00) 
Labels are important, people. 
 
Tanis Kershaw: (20:01) 
It is important. Yeah. So eventually we were able to crack the case. We did get a positive sample and we were able to link it all together. And then it’s been really, it was a great learning because we did make some changes from that. So flour is definitely something we ask all cases now about for any e coli investigations. But also it’s changed public messaging too. So I think before people were, you know, a bit aware of the raw dough being a risk because of the potential for raw eggs. But what this investigation taught us is that raw flour is also a risk. It’s a raw agricultural product. It does need to be cooked. And so, even on the bags, the industry started putting that warning right on the bag that, you know, do not eat raw flour, raw dough. They were updating websites, our own websites were updated, social media. We do know that saying not to eat raw dough is quite controversial. We did get a lot of feedback, I would say, on those social media, a lot of people saying that they would never, ever give that up. And for us, you know what, that’s a choice, right? So our job is to make sure that they have the right information to make that informed decision about their own health.  
 
Michelle Strong: (21:11) 
And on that particular example, how long did it take to identify the source that it was flour?  
 
Tanis Kershaw: (21:17) 
Yeah, so I vividly recall we identified this cluster at Christmas time in 2016 because almost everyone was off. And I remember going, oh, I think we have an outbreak. And it took us from there about two months, about two and a half months before we were able to confirm the source of that outbreak. So this was a longer one.  
 
Michelle Strong: (21:39) 
So what was your example?  
 
Courtney Smith: (21:41) 
The most notable outbreak when I was kind of thinking of all the ones I’ve worked on, I think the most notable for me was an outbreak of e coli in kimchi. This outbreak was more or less the exact opposite of the flour outbreak that Tanis was describing because we solved it in less than 48 hours. So kimchi is, as you can imagine, a more unique exposure. The majority of the population isn’t eating kimchi on a regular basis. So.  
 
(22:07) 
I love kimchi. 
 
Courtney Smith: (22:09) 
Oh, really? Okay. So you’re one of these ones, maybe eating it on a regular basis. But when we had a few cases reporting eating kimchi within the 10 days before they became sick, we knew we were onto something pretty early, and it went very, very quickly from there. So we worked closely with the Canadian Food Inspection Agency and there was a recall of a very specific kimchi product, you know, within the same week that we identified the outbreak and it was removed from the market and nobody else got sick, which was very rewarding for this outbreak in particular because it was a specific strain of e coli that’s known to be very severe. So it was super rewarding that we were able to find the source so quickly. And it was also really interesting because I think many people, including ourselves during this outbreak, thought that an acidic food like kimchi wouldn’t be conducive to bacteria growth. But, you know, we learned that that’s not always the case. And that’s definitely a key takeaway from working in outbreaks for several years, is that you cannot assume anything. So we’re always, always learning as we go.  
 
Michelle Strong: (23:18) 
Are there any other types of challenges with this job?  
 
Fred Jamieson: (23:22) 
Some of the challenges, like as a person doing an investigation, like emotionally challenging, is when there’s illnesses, that are hospitalizations and deaths. So I’ve dealt many investigations where, you know, there were people that passed away. That’s tough because it actually is that manifestation of the food safety risk that we’re trying to protect. So that’s tough.  
 
Angela Catford: (23:44) 
In the last two years, I’ve already got several examples where we’re up at like 2:00 AM to do our risk assessment at Health Canada. It’s all very well defined. We have eight hours turnaround time, so it has to be done basically in one working day. Although when I say one working day, we often receive our requests at the end of the day and our eight hours starts then.  
 
Michelle Strong: (24:08) 
Obviously we don’t want these outbreaks to happen. But when they do, it seems the lessons learned are valuable and they make positive impacts.  
 
Tanis Kershaw: (24:17) 
So every time we have an investigation, we’re always looking at, you know, what did we learn from this? Is there something new that we should be letting people in Canada know about? And, one kind of real-life example of that was in 2021, we investigated an outbreak of salmonella that was found to be linked to frozen corn. And this was the first investigation of salmonella to be found to be linked to any frozen vegetable. So before this, it wasn’t really considered to be, you know, a huge risk. And so we have updated the messaging about this now on the canada.ca website so that people are aware that frozen vegetables do need to be cooked according to the package instructions. They’re not a ready to eat product.  
 
Angela Catford: (25:00) 
In the long term, we all want to work together to make sure it doesn’t happen again. So we try and stop the outbreak at the time that it’s happening, but then we also want to stop future similar outbreaks, and that’s where the partners can also work together and we can, you know, implement food policies that are different. We can do some more research. And there’s definitely work that happens afterwards. But that’s probably about two or three other podcasts worth of information.  
 
Fred Jamieson: (25:30) 
Each one of them brings a different part of the expertise. It’s like, if you want to think baseball or football, each one is a key player on the team, and each one’s important. And if they don’t do their job like they always do very well, we don’t succeed. Things do happen. It takes time. And I understand when people are getting sick, there’s a lack of patience, but you do really want to get it right. You don’t want to make a mistake, you don’t want to recall the wrong thing because it’ll continue to happen. I would put our national food safety emergency response team up against any in the world.  
 
Greg Rogers: (26:03) 
Thank you so much for joining us today. I learned a lot. I just still have this detective kind of pictured in my mind. You know, these cold case files of, you know, unsolved mysteries.  
 
Michelle Strong: (26:18) 
Yeah. Thanks for sharing your knowledge with us on this.  
 
Tanis Kershaw: (26:20) 
Yeah, thank you so much for having us. Yes, thank you.  
 
Fred Jamieson: (26:23) 
I appreciate it.  
 
Angela Catford: (26:25) 
It’s super exciting. Like, I think all of us are really passionate about our job and, and you know, everybody needs to eat and nobody wants to get sick from the food they eat.  
 
Greg Rogers: (26:34) 
Right. For sure.  
 
Michelle Strong: (26:36) 
Foodborne illness outbreak investigations are a team effort across Canada. Local, provincial, territorial, and federal public health units work together to identify the issue and recall all related products.  
 
Greg Rogers: (26:48) 
If you aren’t currently receiving food recalls and alerts, you should really sign up for them. We’ve put the link in our description or in the learn more section on our webpage.  
 
Michelle Strong: (26:59) 
This was inspect and Protect, the Canadian Food Inspection Agency’s official podcast.  
 
Greg Rogers: (27:04) 
Thanks for listening.  
 
Clinton Monchuk: (27:10) 
It’s interesting to hear how foodborne illness investigations span multiple agencies to safeguard public health. Food safety is a collective effort involving federal, provincial, and local health authorities working together to keep Canadians safe. If you want to be proactive and stay informed, consider signing up for the Food Recall alerts on the Government of Canada website. The link is available in our podcast description. Thank you for tuning in and be sure to check out more episodes from Inspect and Protect, the Canadian Food Inspection Agency podcast.  
 
Clinton Monchuk: (27:54) 
I want to thank you for taking the time to listen to our Ask a Farmer podcast. We at Canadian Food Focus value the input from our listeners and ask that you share the podcast with your friends and family. Remember, this is a two-way street, so we seek your input for future segments that are of interest to you about food and farming. To do this, please click on the ‘Ask Us’ icon at the top of our website, canadianfoodfocus.org. While you’re there, feel free to follow our numerous social media links and sign up for our newsletter. This segment was produced and edited by Angela Larson, research and writing by Dorothy Long and Penny Eaton. Music by Andy Elson. I’m your host Clinton Monchuk, and from all of us at Canadian Food Focus, we wish you good health and great eats.