Norovirus Causes, Symptoms and Prevention

Norovirus is the leading cause of food-borne illnesses and hospitalizations in Canada. Learn how to prevent the spread of Norovirus.
October 27, 2019

What is Norovirus?

Norovirus is one virus in a group of viruses that cause gastroenteritis, an illness that usually causes diarrhea and / or vomiting. Norovirus is both very common and very contagious.

In fact, Norovirus is the leading cause of food-borne illness and hospitalizations related to food-borne illness in Canada, due in part to its incredible resilience.

Heat-stable and resistant to cold temperatures, Norovirus is not destroyed or rendered inactive by cooking, refrigerating or freezing. It can survive on virtually any surface for days or weeks, and is frequently transmitted via “low-risk” foods like baked goods and confectionary.

Norovirus is easily spread in commercial food businesses, like restaurants, hotels, event centres and takeaways, and in settings where people are in close contact, such as hospitals, childcare facilities and nursing homes.

Norovirus symptoms

Norovirus symptoms typically begin within 24 to 48 hours of exposure to the virus, but symptoms can start in as little as 12 hours. Symptoms may include:

  • diarrhea
  • stomach cramps
  • nausea, vomiting
  • headache, muscle aches
  • fever, chills
  • fatigue

Some people do not experience any symptoms of illness (‘asymptomatic infection’), but they can still spread the virus to others.

Norovirus transmission

Norovirus is extremely infectious and can easily spread from person to person. The most common routes of infection are:

  • ingestion of contaminated food or water due to poor hygiene practices
  • direct contact with another person who is infected
  • contact with contaminated surfaces or objects (e.g. touching contaminated door handles, utensils or dishware)

In the majority of cases, the virus is spread by Food Handlers who do not practice good hygiene in the workplace, particularly if they do not wash their hands properly after using the bathroom. (Norovirus lives in the intestine, so the stool and vomit of infected people is extremely contagious.)

In some cases, food becomes contaminated at the source; for example, shellfish like clams, oysters and mussels will accumulate the virus in their bodies if the water they live in (and feed on) is contaminated with wastewater or sewage.

When people eat raw shellfish that is contaminated with Norovirus particles, they can become infected. Eating or preparing raw shellfish is not recommended, particularly for people in high-risk groups, like very young children, the elderly, people with weakened immune systems and pregnant women.

People in high-risk groups are more likely to suffer with more serious symptoms of food-borne illness; community organizations that serve food to high-risk groups, such as hospitals and childcare facilities, must maintain extremely high standards of hygiene and food safety training programs.

Norovirus prevention

Good personal hygiene and safe food handling practices are the key to reducing the risk of all food-borne diseases, including Norovirus.

To achieve this, it is critical that all Food Handlers are properly trained in safe food preparation and hygiene. They should also have a good understanding of how infectious agents like bacteria and viruses work — and what they need to survive — in order to reduce food poisoning risks in the business.

In particular, all Food Handlers must be trained to:

  • practice good personal hygiene, particularly hand washing
  • keep raw and cooked / ready-to-eat foods separate
  • thoroughly wash raw fruits and vegetables
  • clean and sanitize all surfaces used for food preparation
  • prevent cross-contamination
  • avoid working with food when they are ill

In most provinces and territories in Canada, a certain percentage of all Food Handlers working in a food business or related organization (‘food premise’) must complete a government-approved food handling course.

In all provinces and territories, Food Handler certification is strongly recommended to ensure safety and compliance with food safety laws and regulations.

Contact the Canadian Institute of Food Safety for more information about food safety training and certification.