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2011-2013 Viral Pathogens and Generic E. coli in Fresh Produce


The Food Safety Action Plan (FSAP) aims to modernize and enhance Canada's food safety system in order to better protect Canadians from unsafe food and ultimately reduce the occurrence of foodborne illness.

In recent years, viruses have been increasingly recognized as a major cause of foodborne illnesses. The viruses most frequently implicated in foodborne illnesses are norovirus (NoV) and hepatitis A virus (HAV) but other viruses such as human rotavirus (HRV) have also been found to be transmitted by food. An expert committee of the FAO/WHO (Food and Agriculture Organization of the United Nations and World Health Organization) recently determined that NoV and HAV in fresh produce were one of the virus-commodity combinations of highest priority in terms of food safety. Numerous outbreaks associated with viral contamination of fresh fruits and vegetables have been reported worldwide over the last decade. Fresh produce can become contaminated with viruses through contact with human sewage or infected workers during primary production, harvest, post-harvest handling, processing, packaging, and distribution. Unlike bacteria, human enteric viruses cannot multiply in food, as they need to enter living human cells to replicate. However, they can remain viable in fruits and vegetables for extended periods of time, and may cause illness if ingested.

Considering the factors mentioned above and their relevance to Canadians, a variety of fresh produce has been selected for enhanced surveillance under the FSAP. Between 2008/09 - 2012/13, about 5,000 samples of fresh fruits and vegetables were collected from Canadian retail locations and tested for the presence of viral pathogens of concern.

The main objective of the 2011/12 and 2012/13 targeted surveys was to generate baseline surveillance data on viral pathogens NoV, HAV and Rotavirus, as well as on generic E. coli, a bacterial indicator of fecal contamination (tested in 2012/13 only), for imported and domestically produced fresh fruits and vegetables available in the Canadian market. In total, 3,339 samples of pre-packaged fresh fruits and vegetables, including imported and domestically produced bell peppers, broccoli, cabbage, organic tomatoes, lettuces, green onions, fresh-cut leafy and non-leafy vegetables and berries, were collected and analyzed. Levels of generic E. coli were found to be acceptable in the 1,959 samples analyzed for this indicator bacteria. HAV was not detected in any of the samples tested, while NoV was detected in 34 samples and HRV was detected in one sample. Positive results indicate that the products came in contact with the virus at some point of the production and distribution chain, suggesting that Good Agricultural Practices (GAPs) or Good Manufacturing Practices (GMPs) were not followed or appropriately implemented. Immediate follow-up activities were not possible as the types of products examined during this survey had a very short shelf-life and were no longer on the market by the time the results were confirmed. No NoV, HRV or HAV outbreaks associated with the consumption of these products were reported in Canada during this survey. As current methods for virus detection are molecular-based assays that do not differentiate live, infectious viruses, from dead viruses, it is not possible to determine whether the positive samples were capable of causing illness based on laboratory results alone. It is important to note that food virology is a fairly emerging field, and that there are currently no internationally recognized assessment criteria and harmonized analytical methods for the detection of viruses in fresh produce.

The Canadian Food Inspection Agency regulates and provides oversight to the industry, works with provinces and territories, and promotes safe handling of foods throughout the food production chain. However, it is important to note that the food industry and retail sectors in Canada are ultimately responsible for the food they produce and sell, while individual consumers are responsible for the safe handling of the food they have in their possession. Moreover, general advice for the consumer on the safe handling of foods is widely available.

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