Noroviruses

This group of viruses are known for causing the ‘winter vomiting bug’ of which there are outbreaks every year usually around January.

The norovirus is responsible for gastroenteritis or ‘stomach flu’ as it is more commonly know. But, if it is caused by contaminated food then it can also be considered a type of food poisoning.

The term ‘norovirus’suggests a single virus but the reality is that these are a group of viruses called noroviruses which are the most common cause of viral food poisoning.

The main problems with this virus include the fact that it is highly infectious, widely spread throughout our environment and difficult to eradicate through normal sanitary and food safety measures.

Anyone can develop norovirus but there are certain groups of people who are at an increased risk of doing so. These include the elderly, young children and people with a compromised immune system (e.g. due to cancer treatment)

History of the norovirus

This virus was initially known as the ‘Norwalk virus’after a town in the USA called Norwalk where the first reported incidence of norovirus occurred.

Since then, there have been outbreaks of this virus on cruise ships, in nursing homes, hospitals and schools. Basically, any place where large groups of people tend to congregate.

As a result of this the term ‘Norwalk’ has been replaced by the term ‘norovirus’.

The norovirus forms part of the Caliciviridae family of viruses which are round or hexagonal in shape and cause a variety of diseases which includes viral food poisoning in humans and foot and mouth in animals.

Causes of norovirus food poisoning

This virus can be easily transmitted in the following ways:

• Contaminated food and/or water
• Personal contact with someone already infected
• Contact with infected surfaces or objects
• Touching or exposure to vomit (from someone who is infected).

Contaminated food and/or water

In reference to contaminated food or water: this includes foods such as salads, vegetables and shellfish. If you share these or any other food with someone who is harbouring this virus then expect to develop norovirus.

This also applies if you eat food or drink water which has been handled by an infected individual.

Another major cause of norovirus is touching a surface or an object which has already been in contact with someone who is infected. This is often the case in large scale outbreaks such as those that happen on cruise liners or in hospitals.

In environments such as these where there are large groups of people, all in close proximity to one another, there is always going to be a risk of viral food poisoning.

If you stop to consider: in any of these environments, large amounts of food are prepared by groups of people and all it takes is for one infected person to handle this food and unwittingly, be responsible for the transmission of this virus.

Any food which they have prepared or cooked will now be contaminated by this virus which will spread to another person during consumption.

Personal contact with someone already infected

It is easy to contract this virus if you come into contact with someone who is already infected. Both of you may be unaware of this but if you touch hands or engage in any other type of personal contact then this will help to spread the virus.

Contact with infected surfaces or objects

If the infected person touches a surface, door handle or any object which will be touched by thousands of others then this will ensure that the virus is able to spread to lots of people.

Touching or exposure to vomit

This is another cause of norovirus. This virus can be transmitted between people due to exposure to infected vomit.

For example, if you work in a nursing home and clean up after someone who has been sick due to norovirus then be aware that this places you at risk of contracting this virus.

This applies to faeces as well. Both of these are ideal forms of transmission for norovirus.

Symptoms of norovirus food poisoning

This is a short lived infection although it can persist in high risk individuals. The incubation period is usually 24 to 48 hours after the initial exposure and the illness itself lasts for around two to three days.

Symptoms include:

• Fever
• Headache
• Abdominal pain
• Nausea
• Vomiting
• Diarrhoea
• Loss of appetite
• Fatigue

Most people recover from this infection within a few days and without any long term effects. Complications are rare but there is one which you need to be aware of which is dehydration.

Dehydration can be treated at home but severe cases will require hospitalisation.

Treatment for norovirus food poisoning

There is no specific treatment for norovirus per se but there are a few ways of easing the symptoms. These include drinking plenty of fluids and taking re-hydration powders to top up depleted vitamin and mineral levels.

These powders contain electrolytes which are needed to replace those lost as a result of vomiting and diarrhoea. These powders can be bought at a local pharmacy or online.

Get lots of rest during this period.

Contact your GP for further advice.

Preventing norovirus food poisoning

The difference between norovirus and bacterial food poisoning is that norovirus does not reproduce within food –which bacteria do. Plus cooking food at the correct temperature will destroy this virus.

So, the message here is to cook any food thoroughly and at the right temperature. Do not be tempted to consume any food which has not been cooked for the right length of time.

This is especially important in the case of shellfish, e.g. oysters which are notorious for causing food poisoning. It is impossible to distinguish between a safe oyster and a contaminated one so cook these thoroughly to be on the safe side.

Wash your hands before preparing food. Also wash any salads and vegetables before use.

Always wash your hands after visiting the bathroom and if you have been in contact with an infected person.

Note: you do not develop immunity to norovirus. If you develop this infection then be aware that it is possible to contract this again at some point in the future.