Foodborne viruses are a worldwide health concern, with types, severity and impacts of illness changing over time and across communities and countries.

Dr. Shannon Majowicz, associate professor in the School of Public Health Sciences, joined the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) in Rome, Italy last month for a Joint FAO/WHO Expert meeting on Microbiological Risk Assessment (JEMRA) of viruses in foods.

During the meeting, the expert committee conducted a global review, looking at the frequency and clinical severity of viruses associated with foodborne illnesses in humans. They highlighted that norovirus was the leading cause of viral foodborne illness, followed by hepatitis A and hepatitis E.

Shannon Majowicz

“Norovirus is not only highly contagious, but you can also get sick from a very small amount,” says Majowicz. “Data from 2010 told us that there are about 125 million cases each year worldwide, with 35,000 deaths. The World Health Organization’s Foodborne Disease Burden Epidemiology Reference Group is now working on updating these estimates with data from more recent years.”

When looking at clinical severity alone, hepatitis A and E are ranked highest.

“Hepatitis E is not as big of an issue in Canada as it is in some other countries,” says Majowicz. “The virus that causes the most foodborne illness will vary by country and over time.”

Majowicz explains that both norovirus and hepatitis A are spread by food and water contaminated with infected feces. The committee found that the foods with the highest global public health risk associated with these two viruses include prepared food, frozen berries and shellfish, with substantial differences by region.

Hepatitis E differs in that it is a zoonotic pathogen, meaning it can be passed from animals to humans. While the virus can be transmitted through contaminated food and water, it is also associated with animal products. Experts concluded the foods with the current highest global public health risk of hepatitis E are pork and wild game.

“One of my main areas of expertise is disease burden, which means to understand how big of a problem foodborne infections like these viruses really are,” says Majowicz. “This includes not only how many cases or fatalities, but any lasting health consequences, short- or long- term. For example, one of the long-term impacts of hepatitis A for some people is liver problems.”

While there are currently no approved vaccines for hepatitis E or norovirus in Canada, hepatitis A is highly preventable with the hepatitis A vaccine.

Food and Agricultural Organization of the United Nations logo statue.

Before joining Waterloo, Majowicz worked with the federal government for more than 10 years in the public health sector and has been a member of the WHO’s Foodborne Disease Burden Epidemiology Reference Group since 2021. She runs the Foodborne Disease Epidemiology Group at Waterloo. She is one of two Canadians on the panel of 23 experts from around the world.

The committee recommends all member countries continue to adopt methods for detecting viruses in foods with the hope of enhancing knowledge on food attribution and risks.

Read the meeting summary here.