Trading Standards Institute Advice

Food borne illness and contamination: norovirus

This leaflet is for all food businesses, including those involved in catering, food production, food preparation, retail premises, restaurants, pubs, cafes, and fast-food shops.

What is norovirus?
Norovirus (which used to be known as norwalk) is a viral infection that causes acute intestinal upset. Common names for illness caused by norovirus are the winter vomiting disease, gastroenteritis, non-bacterial gastroenteritis, stomach flu or what's often called a 'tummy bug'.

The illness usually lasts two to three days and there are no long-term health effects. Anyone can be infected at any age. Being immune to the disease after having been infected does not last long. People can have several infections over their lifetime.

Why does norovirus matter?
Norovirus is the most common cause of diarrhoea and vomiting in England and Wales and is highly infectious.

A virus, unlike a bacteria, does not need warmth, food and moisture to multiply, it just needs a living host, which means it needs to get into your system. It may use food and water as a 'vehicle' to do this, but viruses can easily move from person to person using the faecal oral route - which is where contaminated faeces from an infected person gets into the digestive system of another person. This means that norovirus can be easily passed on by someone who uses the toilet but does not wash their hands and then touches door handles, taps and food.

There is also a risk of infection when organisms are released into the air - for example, from projectile vomiting.

The number of particles needed to cause infection is very low (and can be as few as 10). The number of outbreaks of norovirus are highest in the winter as viruses thrive in cold conditions and are not destroyed by freezing.

When a person is infected with the virus, the virus starts to multiply in the small intestine. This is known as the incubation period. After 24 to 48 hours the symptoms can appear, and usually include projectile vomiting, diarrhoea, fever, headache, muscle aches and abdominal pain. The illness usually lasts 24 to 60 hours, although sufferers may feel weak and unwell for several days after the symptoms have stopped. Symptoms may last for up to two weeks. People rarely die from norovirus, but vulnerable people such as the elderly, very young or those with weak immune systems may be at greater risk and will certainly feel very poorly.

Outbreaks of the virus are common in places we refer to as 'semi-closed' environments such as residential care homes, hospitals, prisons, cruise ships, schools and nurseries. The profile of the infection will mean that instead of everyone getting ill at a similar time, a 'domino' effect will be seen over a period of several days.

What do I need to do in my food business?
You need to be aware that norovirus is highly contagious. In an outbreak in the Netherlands, it was worked out that on average each ill person infected 2 other people. The virus spreads quickly and is a serious risk to every food business.

There are several areas for control

By law, food handlers must report any health issues to their supervisor, manager or 'business operator'. (The business operator is often the business owner.)

You should encourage them to do this even if they are not sure whether there is a risk. Once reported, the first step is to keep the food handler away from food. This means they cannot touch or come into contact with food, food surfaces or anything that comes into contact with food - so no washing up.

Many norovirus outbreaks have been traced back to food that was handled by only one person. The food handler cannot start food handling or come into contact with food until they have had no symptoms for at least 48 hours.

Food handlers need to wash their hands thoroughly and frequently with antibacterial soap. This is very important to help to stop the virus spreading.

You should make sure food handlers know how and when they should be washing their hands and how important it is to wash their hands after they have used the toilet. They should wash their hands twice - once in the toilet area and again when they return to the food handling area.

You should show food handlers how to wash their hands properly - how to cover all areas of their hands and how long it should take (around 30 seconds to wash, then rinse and dry).

You should check how much soap and how many paper towels are being used, as this will show whether food handlers are washing their hands often enough.

Alcohol wipes and gels may not be effective and are not a substitute for washing your hands. Disposable gloves can be used, but you still need to wash your hands frequently.

It is very important that you clean and disinfect any surfaces where the virus may be present.

A detergent will break down and remove grease and dirt, but will not destroy the viruses. Viruses are microscopic, so surfaces may look clean but could still be highly contaminated.

Disinfection will reduce harmful organisms to a safe level, and is a very important part of controlling the virus.

You must disinfect any surfaces and equipment that come into contact with food.

Chlorine-based disinfectants are more effective against viruses.

Any food can be contaminated with the virus by an infected food handler, but foods that are handled, such as ice, fruit, desserts, cold meats and prepared salads are among the most common high-risk foods.

However, some foods themselves can be a problem. Shellfish are often associated with the virus, particularly those that are eaten raw, such as oysters.

The virus will not survive temperatures above 60°C and so will be destroyed by the right cooking and reheating (to a minimum temperature of 75°C).

Make sure that you buy food such as salad and fruit from a supplier who has a good reputation, and that you wash it thoroughly before you use it.

You need to know where the shellfish came from and how it was supplied. This is particularly important if the shellfish is going to be eaten raw, such as oysters.

Shellfish must be caught or farmed in clean waters and not areas that may be contaminated by sewage.

It must also be stored away from high-risk food such as cooked meats, cooked fish, dairy products and cooked rice.

More information
You will find further guidance in our other leaflets on this website. Information can also be found on the Food Standards Agency website.

Alternatively, contact your local environmental health service for advice.

Please note
This leaflet is not an authoritative interpretation of the law and is intended only for guidance.

© 2018 itsa Ltd.