Food Safety - Foodborne Illness


Food Safety - Foodborne Illness Background 



Importance of Topic to Practice
Food-related illnesses have been documented since early times, with Hippocrates (460 B.C.) reporting a strong correlation between food consumed and human illness (1). Today, foodborne pathogens (including norovirus, Salmonella, Clostridium perfringens, Camplylobacter, Staphyloccus aureus and Esherihia coli) are a major factor affecting food safety and causing illness, which has significant impact on health and the economy (1,2). The WHO indicates that there are over 600 million cases of foodborne diseases worldwide with over 400,000 deaths (3). In Canada, more than 4.0 million Canadians get food poisoning annually (4,5) while in Australia the incidence is about 5.4 million (4). The U.K. estimates about 2.4 million annual cases of foodborne illness (6,7). Foodborne illnesses can be prevented and controlled by following safe preparation, handling, storage and cooking guidelines and techniques. Dietitians can play an important role in educating the public about how to prepare food safely to reduce the risk of foodborne illnesses. 
Topic Overview
What are foodborne illnesses and how does infection occur?
Foodborne illnesses (also referred to as food poisoning or foodborne disease) are infections or irritations of the gastrointestinal tract caused by food or beverages that contain harmful bacteria, parasites, viruses or chemicals (1,2). Foodborne illnesses can be caused by either the ingestion of a toxigenic pathogen that establishes itself in the human host (foodborne infection) or when that pathogen produces a toxin in the gastrointestinal tract (toxico-infection) or when the pathogen establishes itself in a food and produces a toxin that is then ingested and subsequently causes illness (food intoxication). 
There are over 250 types of foodborne pathogens that can cause foodborne illnesses (2,8). Bacteria (66%) and their toxins, chemicals (26%), viruses (4%), and parasites (4%) are the main causes of foodborne illnesses (2). Incubation period varies between organisms and can range from several hours to several days, and several weeks with parasites.   
Some pathogenic bacteria are capable of spore formation and are highly heat resistant (e.g. Clostridium botulinum, C. perfringens, Bacillus subtilus, Bacillus cereus), while others are capable of producing heat-resistant toxins (e.g. Staphylococcus aureus, Clostridium botulinum) (1). Most pathogens are mesophilic (growing best at a moderate temperature) with an optimal growth temperature ranging from 20°C to 45°C. However, some pathogens such as Listeria monocytogenes and Yersinia enterocolitica are capable of growth in refrigerated conditions or temperatures less than 10°C.
Common Foodborne Pathogens and Primary Sources
Worldwide, the most common foodborne pathogenic bacteria that result in illness and death include Staphylococcus aureus (S. aureus), Salmonella spp., Campylobacter spp., Listeria monocytogenes and E.coli (2). Other common pathogens of concern include Bacillus cereus, Clostridium botulinum, Clostridium perfringens, Cronobacter sakazakii, Shigella spp., Vibrio spp. and Yersinia enterocolitica; hepatitis A and noroviruses viruses; and Cyclospora cayetanensis, Toxoplasma gondii and Trichinella spirals parasites (1).
Foods most implicated in foodborne illnesses include raw or undercooked meat, poultry, shellfish or eggs and their products; ready-to-eat deli meats; raw milk and dairy products; raw or unwashed prepackaged fruit and vegetables (especially leafy vegetables); and leftovers not cooled and reheated properly (1,2,9).
In Australia, the most common foodborne pathogens are norovirus, pathogenic Escherichia coli, Campylobacter spp. and non-typhoidal Salmonella spp., although approximately 80% of illnesses are by unknown pathogens (10).
In Canada, norovirus (65%)  is the primary cause of foodborne illness and hospitalization, followed by Clostridium perfringens (11%), Campylobacter spp. (8%), Salmonella spp. (non-typhoidal) (5%) and Staphylococcus aureus. Pathogens that are less frequent but can lead to more serious cases of foodborne illness requiring hospitalization include Clostridium botulism, Listeria monocytogenes, Escherichia coli, Vibrio spp., Cronobacter, Cyclospora and Shigella (5)Hepatitis A and E are also considered a common type of foodborne illness in Canada. 
For more information about specific pathogens, refer to:
Common causes of foodborne pathogens in New Zealand include norovirus, Clostridium difficile, Campylobacter spp., Salmonella spp. (non- typhoidal), Shigella, Listeria and Giardia (11).
In the United Kingdom, the most common foodborne pathogens are Campylobacter and norovirus, followed by Clostridium perfringens and Salmonella (6).
How are foodborne pathogens transmitted into the food system? 
Most foodborne pathogens have a zoonotic (animal) origin and animal foods and their products are major vehicles of the transmission of foodborne illnesses (1,2). Animal products are a primary source of foodborne illness because pathogens find the high protein and lipid environment an ideal environment for growth (2). The contamination of food can occur during the growth, harvesting or slaughter, processing, storage and/or shipping of the food as well as the preparation and the consumption of the food (2,4). The transmission of pathogens can be spread by contaminated drinking water and food; animal feces; scratches or bites; ticks, fleas, mosquitoes or rodents; soil and water; or human contact (e.g. farmers, workers etc.) and cross-contamination through unsanitary food handling practices. (e.g. not thoroughly washing hands, using contaminated cutting boards or utensils) or improper storage (2,4). The risk of food contamination depends largely on the health status of food handlers, their personal hygiene, knowledge, and practice of food hygiene (2). 
Is there a smell, taste and change in appearance of food associated with the risk of foodborne illness? 
Foodborne pathogens are not visible to the naked eye and are not associated with a change in smell, taste or appearance (12-14). However, bacteria, yeasts and moulds that spoil food can cause a change in odour, taste, colour or appearance (15-17). Food spoilage is a process that changes the physical and chemical properties of a food, making it unfit for consumption (15,16,18). While mainly caused by bacteria, yeasts and mould, it can also be caused by light, oxygen, heat, humidity, temperature or a combination of any of these factors (15,18). Food spoilage bacteria are not associated with foodborne illnesses (12). Like foodborne pathogens, good food handling and storage practices reduce the risk of food spoilage. 
What are the symptoms of foodborne illness and who are the vulnerable populations?
The symptoms of foodborne illnesses can vary from mild to severe and may differ depending on the type of foodborne illness (8,19). Symptoms may take hours or days to develop. Time of onset may depend on the type of pathogenic infection.  
Common symptoms include (8,19,20): 
  • upset stomach
  • stomach/abdominal cramps
  • nausea
  • vomiting
  • diarrhea 
  • fever
  • chills
  • headache.
Severe symptoms of foodborne illnesses include (19): 
  • dehydration
  • high fever 
  • diarrhea lasting longer than three days
  • bloody diarrhea 
  • frequent vomiting. 
Serious side-effects and/or long-term complications include (2,19): 
  • Guillain-Barre syndrome
  • Reiter’s syndrome, which can lead to chronic arthritis
  • brain and nerve damage
  • hemolytic uremic syndrome (HUS), which could cause permanent renal failure
  • septicemia. 
High risk or vulnerable groups for foodborne illness due to an altered or compromised immune system include (21): 
  • adults 60 and over
  • women who are pregnant
  • individuals with weakened immune systems
  • children aged five years and younger.

What are consumer household tips on how to reduce the risk of foodborne illnesses?
Proper preparation, handling, cooking and the storage of foods can help to prevent and reduce the risk of foodborne illness by reducing the spread and cross-contamination and eliminating potential pathogens (2). Safe food handling steps include (13,22):  
  1. Keeping food preparation areas clean: 
  2. Cooking meat, fish and poultry to the recommended internal temperature. The range of safe internal temperature is between 71-84°C; however, this differs depending on the cut and type of product. Colour and texture are unreliable indicators that a product is safe to eat. 
  3. Storing foods to keep them safe:
  4. Thawing foods in a safe way. To learn more about how to safely defrost meat, fish and poultry, refer to: or
  5. Keeping leftovers safe. For more information about practices to keep leftovers safe and fresh, refer to:
What are the risks of eating raw fish or shellfish (i.e. sushi, ceviche, oysters)?
Raw Shellfish
Health Canada reports that raw bivalve shellfish such as oysters, clams, scallops, mussels and cockles can carry bacteria, viruses and toxins that can cause foodborne illness if they are not stored, handled or prepared appropriately (23). Vibriosis is a common foodborne bacteria that can infect individuals who eat raw oysters (24,26). These bacteria can occur naturally in coastal waters where oysters grow (24,25). In particular, children, women who are pregnant, the elderly and individuals with weakened immune systems (including those with liver diseases) are more susceptible to foodborne illness and should avoid eating raw or undercooked bivalve shellfish (24,25). To reduce risk, individuals should (25): 
Raw Fish
Eating raw fish used in sushi and sashimi increases the risk of foodborne illness due to foodborne pathogens (12). Risk arises from food preparation methods and the risk of infective parasites found in fresh raw fish or lightly cooked fish. The four main types of parasites of concern are cestodes (tapeworms like Diphyllobothrium), trematodes (flukes), nematodes (i.e. roundworms such as anisakids) and Myxosporidia, with parasitic tapeworms being the most common (12). Anisakiasis is the most common parasitic infection (caused by the anisakid roundworm) associated with sushi eating (27); however, cases in Canada are rare (28). Different countries around the world (i.e. the U.S., EU, Hong Kong, Canada, Australia and New Zealand) have specific food safety guidelines in place to reduce the risk of foodborne pathogen contamination in raw fish and thereby reduce the risk of foodborne illnesses (12). Regulations and measures are in place in order to control raw fish, seafood and their products at their place of harvest, processing and arrival at marketing or in restaurants (12). To prevent parasitic foodborne illnesses from the Anisakis spp., the EU and U.K. have current regulations that require all fish for raw consumption must be frozen to a core temperature of minus 20°C for at least 24 hours. Atlantic farmed salmon is exempted due to the use of formulated feed, which reduces the risk of parasite contamination (26,27). In North America, most fresh fish are frozen at -20°C for five to seven days or blast frozen; blast freezing at -35°C for 15 hours and then being held at -20°C for 24 hours will kill anisakid larvae (27,28). Sushi chefs have been trained to look for potential parasite contamination (28). 
In Canada, rules regarding sushi and sashimi are province specific. Alberta, British Columbia, Manitoba and Nova Scotia have guidelines that include that fish must be from approved sources, confirmed as “sushi-grade” and parasite free (29-32). Depending on the type of fish, some types of fish must be frozen first, to obtain sushi-free grade status, to reduce the risk of infective parasites such as the anasikid roundworm and Diphyllobothrium. Several large types of tuna or other types of large fish are exempt, as are fish from aquaculture that have been fed formulated feed verified as parasite free. While Ontario does not have specific guidelines, Ontario Public Health undertook a narrative literature review (up to March 2017) and, based on the evidence, suggests that freezing provides an effective way to inactivate parasites in raw and undercooked food (33). Following recommended food preparation guidelines will also reduce the risk of contaminating fish with other foodborne pathogens (12,26). 

For more information about shellfish food safety, refer to: 
For more information on safe sushi/sashimi:


Resources for Professionals
Clinical practice guidelines, web links and other professional tools and resources can be found under the Food Safety - Foodborne Illness Related Tools and Resources tab. Use the Audience, Country and Language sort buttons to narrow your search. 
  1. Bintsis T. Foodborne pathogens. AIMS Microbiol. 2017 Jun 29;3(3):529-563. doi: 10.3934/microbiol.2017.3.529. PMID: 31294175; PMCID: PMC6604998. Abstract available from:
  2. Abebe E, Gugsa G, Ahmed M. Review on Major Food-Borne Zoonotic Bacterial Pathogens. J Trop Med. 2020 Jun 29;2020:4674235. doi: 10.1155/2020/4674235. PMID: 32684938; PMCID: PMC7341400. Abstract available from:
  3. World Health Organization. Estimating the burden of foodborne disease. 2021. Available from:
  4. Chlebicz A, Śliżewska K. Campylobacteriosis, Salmonellosis, Yersiniosis, and Listeriosis as Zoonotic Foodborne Diseases: A Review. Int J Environ Res Public Health. 2018 Apr 26;15(5):863. doi: 10.3390/ijerph15050863. PMID: 29701663; PMCID: PMC5981902. Abstract available from:
  5. Government of Canada. Yearly food-borne illness estimates for Canada. 2016. Available from:
  6. Holland D, Thomson L, Mahmoudzadeh N, Khaled A. Estimating deaths from foodborne disease in the UK for 11 key pathogens. BMJ Open Gastroenterol. 2020 Jun;7(1):e000377. doi: 10.1136/bmjgast-2020-000377. PMID: 32586945; PMCID: PMC7319714. Abstract available from: 
  7. Food Safety Agency. FSA research suggests new higher estimates for the role of food in UK illness. 2020 Feb 20. Available from:
  8. Switaj TL, Winter KJ, Christensen SR. Diagnosis and Management of Foodborne Illness. Am Fam Physician. 2015 Sep 1;92(5):358-65. PMID: 26371569. Abstract available from: 
  9. Center for Disease Control and Prevention (CDC). Foods that Can Cause Food Poisoning. 2020 Oct 1. Available from: 
  10. Health Navigator New Zealand. Food Safety. 2021 Feb 25. Available from:,%2C%20shigella%2C%20salmonella%20and%20listeria.  
  11. Australian Government: Foodborne illness in Australia (2010). 2014. Available from:$File/Foodborne-Illness-Australia-circa-2010.pdf 
  12. Lehel J, Yaucat-Guendi R, Darnay L, Palotás P, Laczay P. Possible food safety hazards of ready-to-eat raw fish containing product (sushi, sashimi). Crit Rev Food Sci Nutr. 2021;61(5):867-888. doi: 10.1080/10408398.2020.1749024. Epub 2020 Apr 9. PMID: 32270692. Abstract available from:
  13. Government of Canada. Food Safety and You. 2021 Jan 18. Available from:
  14. USDA Food Safety and Inspection Service. Safe minimal internal temperature. 2020 May 11. Available from: 
  15. Magoulas A. Food Safety and Inspection Service. Protecting Your Family from Food Spoilage. 2017 Feb 21. Available from:,factors%2C%20foods%20will%20gradually%20deteriorate.
  16. Government of Ontario. Ministry of Health and long term care. Food Safety: A Guide for Food Handlers. 2018 September. Available from:
  17. Canadian Institute of Food Safety. Perishable foods and food spoilage. [cited 2021 Jun 1]. Available from: 
  18. Blackburn, C. D. W. 2006. Food spoilage microorganisms. In Woodhead publishing Series in food science, technology and nutrition, 695–712. Cambridge, UK: Woodhead Publishing; 2006. Available from:
  19. CDC. Food poisoning symptoms. 2021 Mar 9. Available from:
  20. Government of Canada. Food-related Illnesses. 2013 Aug 23. Available from:
  21. Government of Canada. Food Safety for Vulnerable \Populations. 2019 Sep 27. Available from: 
  22. CDC. Four Steps to Food Safety. 2020 Aug 4. Available from: 
  23. Government of Canada. Shellfish food safety. 2011 Nov 22. Available from: 
  24. CDC. Oysters and Vibriosis. 2020 Jun 26. Available from:
  25. Government of Canada. Vibrio. 2021 Jan 18. Available from:
  26. Hoel S, Vadstein O, Jakobsen AN. The Significance of Mesophilic Aeromonas spp. in Minimally Processed Ready-to-Eat Seafood. Microorganisms. 2019 Mar 23;7(3):91. doi: 10.3390/microorganisms7030091. PMID: 30909614; PMCID: PMC6463141. Available from: 
  27. Iwata K, Fukuchi T, Yoshimura K. Is the quality of sushi ruined by freezing raw fish and squid? A randomized double-blind trial with sensory evaluation using discrimination testing. Clin Infect Dis. 2015 May 1;60(9):e43-8. doi: 10.1093/cid/civ057. Epub 2015 Feb 18. PMID: 25697740; PMCID: PMC4392844. Available from:
  28. Weir E. Sushi, nemotodes and allergies. CMAJ. 2005 Feb 1;172(3):329. doi: 10.1503/cmaj.045207. PMID: 15684113; PMCID: PMC545753. Available from: 
  29. Alberta Health Services. Guidelines for preparing Sushi Products. 2016 Apr. Available from:
  30. BC Centre for Disease Control. Sushi Safety. [cited 2021 Jun 1]. Available from: 
  31. Manitoba Health. Food Safety guidelines for the Preparation of Sushi. 2013 Dec. Available from:
  32. Nova Scotia Department of Agriculture. Sushi/Sashami Preparation Guidelines. 2011 Jul. Available from:
  33. Public Health Ontario. Evidence Brief: Control of parasites by freezing in fish for raw consumption. 2017. Available from:

Target Group: All Adults, All children(0-12 yr.), Youth(13-17 yr.)
Knowledge Pathways: Food Safety - Foodborne Illness
 Last Updated: 2022-01-05

Current Contributors


Christine Mehling - Author

Cathy Chenhall - Reviewer