“I love what I do. I think that we can make a difference.” As a senior program specialist at PHO, Yvonne Whitfield is part of a team that leads investigations related to food, animal and waterborne illness. “One of the things we know about these illnesses is that we only see a small number of the cases—most go unreported. So when you prevent one, you prevent many more. That is what drives me, knowing that we are helping so many more people than those cases that are reported to us.”
Her early years in Jamaica led to her career in public health. “In a developing country, conditions are not always optimal. I remember the health inspector coming around, and he made such an impact when he came into the schools.” Whitfield eventually became a public health inspector and earned her master of public health degree. For over 25 years, Whitfield has led investigations across Ontario at the local and provincial levels.
What does a typical foodborne illness investigation involve? It starts with the team, which is usually comprised of a program specialist, an epidemiologist, a health analyst, a public health physician, and laboratory experts. No investigation is typical, Whitfield says, but there are many things investigators look at when trying to solve an outbreak. “In investigations, we work with many others, such as local public health units and food safety and community partners. Foodborne outbreaks are often very complex and involve multiple stakeholders at all levels. Public health units are often the first contact with the case and typically interview impacted people in their homes or in hospitals, sometimes multiple times as the investigation evolves. After collecting food samples they look at people’s habits—what have they been exposed to? What did they eat? Did they attend a function? Did they travel? Are animals in the home? We look at things like shopping records, loyalty card data, activities and routines, as well. Then we put all that information together to identify, understand and help manage outbreaks.”
Whitfield says her days are never the same, and often require her to go non-stop. “The work is interesting. I never have to look at the clock. I often feel like we are on a roller coaster ride because of the outbreaks—but it’s interesting. We’re detectives searching for answers.”
She says investigating a recent outbreak of listeriosis, eventually associated with chocolate milk, was incredibly challenging. The team was trying to pinpoint the source of people’s illness, initially thinking it was related to another outbreak happening south of the border. Listeriosis is less common in winter, she notes, and many assumed it was related to imported southern produce.
Whitfield says that’s when PHO’s lab data played a critical role in the investigation: the DNA fingerprint revealed through whole genome sequencing wasn’t the same as the produce that had been identified as a source in the US. So the team continued to look for other leads, often leading to “dead ends,” and finally got a break when some of the clues pointed to a particular brand of milk from one particular grocery store chain. “We went to the store and met with the staff. They mentioned milk,” she says. “But imagine how many people drink milk? How to tease out who did and did not drink one particular brand of milk was a challenging task.” Local public health investigators were asked to collect milk samples from the homes of affected people, and one came up as linked to the DNA in our lab tests. In the end, the Canadian Food Inspection Agency confirmed chocolate milk as the culprit.
“You can’t solve everything—but I try. I go out, I go to stores, look at products, and try to figure it out. Solving a foodborne illness investigation really is a massive collaboration among partners. We collaborate with everyone, from our lab colleagues who fingerprint diseases, to our local health unit partners who are on the ground, investigating, and to our partners in provincial ministries and the federal government who look at the big picture. We all try to make a difference for people who are suffering. The thanks and gratitude we receive from people whose lives are affected tells me we are.”