Unravelling the mystery of food-borne illness outbreaks: Disease detectives search for clues in the data

At the Public Health Agency of Canada (PHAC), epidemiologists play an important role in protecting the health of Canadians as they study patterns of disease so they can understand what causes an illness and how best to prevent it. Epidemiologists can work on all types of health-related issues including infectious diseases, chronic diseases, and injuries, to name a few.

The Outbreak Management Division (OMD) at PHAC investigates multi-jurisdictional outbreaks that cause enteric illness, often through food or animals contaminated with bacteria such as Salmonella and E.coli.

Joyce Cheng is the manager of the Response team at OMD and her team’s main responsibilities include the collection, management, analysis, and interpretation of data to find the source of the outbreak. Data collection refers to gathering as much information as possible about an outbreak, including designing a questionnaire to interview individuals with an illness about their exposures before becoming sick. Once the team has gathered information, they ensure all this data is entered into one common database so that it is easier to manage and analyze.

When analyzing the data, Cheng and her team put on their “detective hats” and look for commonalities in the data.

“Did some individuals purchase the same food at the same store? Did individuals eat at the same restaurant? Is it unusual to see this many individuals reporting the same food? These are just some of the questions we ask when analyzing and interpreting the data to find the source of an illness. If a source is identified, we can inform the public through a public health notice, and the food may be recalled which can help protect and prevent illness in Canadians across the country,” explains Cheng.

Cheng has worked at OMD for over 11 years, starting as a student and working her way up to her current role as manager. Cheng’s career progressed towards epidemiology naturally; as she studied health sciences at McMaster University and went on to do her Master of Public Health degree at the University of Waterloo. During her Masters, she took courses in epidemiology and then did her practicum placement at OMD, which really fuelled her interest in the field. Now in her current position, she enjoys the detective work involved in investigating an outbreak because she gets to use critical thinking and problem solving skills on a daily basis.

OMD has investigated numerous outbreaks with some resulting in upstream changes to prevent illnesses from occurring. One example of this was when the team investigated many Salmonella outbreaks associated with frozen, raw breaded chicken products such as chicken nuggets and chicken strips. The team was able to identify the link between illnesses and these products, leading to several food recall warnings and new industry requirements to control Salmonella in these products.

It is estimated that one in eight Canadians will get a food-borne illness each year, with symptoms ranging in severity from a mild illness to hospitalization or death. Cheng and her team at OMD work hard to reduce the risk of these illnesses by investigating outbreaks and using data for action to prevent others from getting sick.