Norovirus: Causes, Symptoms and Prevention

Norovirus affects 1.8 million Australians each year. Learn how to prevent Norovirus in your workplace.
Norovirus: Causes, Symptoms and Prevention
February 19, 2020

What is Norovirus?

There are an estimated 1.8 million cases of Norovirus infection in Australia each year, making it the most common cause of gastroenteritis, an illness that typically causes vomiting and/or diarrhoea. Norovirus is extremely contagious.

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 biscuits, crackers and sweets.

In Australia, Norovirus outbreaks are most commonly reported in restaurants and other food service businesses as well as institutions, such as aged care and childcare centres, summer camps and hospitals. From 1999–2003, three confirmed Norovirus outbreaks were reported on cruise ships visiting Sydney.

Symptoms of Norovirus

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:

  • diarrhoea
  • 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.

How Norovirus is spread

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 practise 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, even if the person has no symptoms of illness themselves.)

For example, two major Norovirus outbreaks in 2003 were linked to foods that required considerable handling; one outbreak was linked to a commercial caterer, and the other to contaminated ready-to-eat baked goods. According to OzFoodNet’s 2004 Annual Report, both outbreaks were caused by Food Handlers who had worked while ill with gastroenteritis.

Some foods can also become contaminated during growing or processing; for example, marine 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. Consumption of raw oysters as the vehicle of transmission in Norovirus outbreaks has been reported in the Northern Territory (NT), Queensland (QLD) and New South Wales (NSW).

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 organisations 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.

How to prevent Norovirus

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:

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

In most states and territories in Australia, commercial food businesses and related organisations must appoint a Food Safety Supervisor to take control of food safety in the facility in order to minimise food safety risks and prevent food-borne illness outbreaks.

Food Safety Supervisors are required to complete a nationally recognised Food Safety Supervisor course that is accepted by local health authorities, such as AIFS’ online Food Safety Supervisor course.

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

Contact the Australian Institute of Food Safety (AIFS) for more information about food safety training and certification.